New upstream version 2.15.0

75 files changed, 795 insertions, 475 deletions

diff --git a/CHANGES.md b/CHANGES.md
index 9a593ae..acdc023 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,12 @@
+2.15.0 (2023-10-26)
+-------------------
+
+* atddiff: Breaking changes in the JSON output format of atddiff (#382)
+* atddiff: Fix `atddiff --version` output (#379)
+* atddiff: New experimental option `--no-locations` aimed at
+           producing more stable results that allow diffing successive
+           atddiff reports to spot new findings and ignore old ones (#377)
+
 2.14.1 (2023-10-20)
 -------------------
 
diff --git a/atd.opam b/atd.opam
index 8ff195d..01b7937 100644
--- a/atd.opam
+++ b/atd.opam
@@ -1,4 +1,4 @@
-version: "2.14.1"
+version: "2.15.0"
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
 synopsis: "Parser for the ATD data format description language"
diff --git a/atd/src/version.ml b/atd/src/version.ml
index ab1c248..ba7c4aa 100644
--- a/atd/src/version.ml
+++ b/atd/src/version.ml
@@ -1,3 +1,3 @@
 (* The version string is replaced by the actual version at release time
    by 'dune release'. *)
-let version = "2.14.1"
+let version = "2.15.0"
diff --git a/atdd.opam b/atdd.opam
index df066e4..7ccb5b1 100644
--- a/atdd.opam
+++ b/atdd.opam
@@ -1,4 +1,4 @@
-version: "2.14.1"
+version: "2.15.0"
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
 synopsis: "DLang code generation for ATD APIs"
diff --git a/atdd/src/lib/Version.ml b/atdd/src/lib/Version.ml
index ab1c248..ba7c4aa 100644
--- a/atdd/src/lib/Version.ml
+++ b/atdd/src/lib/Version.ml
@@ -1,3 +1,3 @@
 (* The version string is replaced by the actual version at release time
    by 'dune release'. *)
-let version = "2.14.1"
+let version = "2.15.0"
diff --git a/atddiff/src/bin/Atddiff_main.ml b/atddiff/src/bin/Atddiff_main.ml
index c3f5629..b052e8c 100644
--- a/atddiff/src/bin/Atddiff_main.ml
+++ b/atddiff/src/bin/Atddiff_main.ml
@@ -12,6 +12,7 @@ type conf = {
   filter: Atddiff.filter;
   json_defaults_old: bool;
   json_defaults_new: bool;
+  with_locations: bool;
   output_format: Atddiff.output_format;
   exit_success: bool;
   version: bool;
@@ -32,11 +33,13 @@ let exit_info = [
   finding_exit, "atddiff successfully found one or more issues to report.";
 ] |> List.map (fun (code, doc) -> Cmd.Exit.info ~doc code)
 
+let print_version_and_exit () =
+  print_endline Atddiff.version;
+  exit ok_exit
+
 let run conf =
-  if conf.version then (
-    print_endline Atddiff.version;
-    exit ok_exit
-  )
+  if conf.version then
+    print_version_and_exit ()
   else
     let out_data =
       Atddiff.compare_files
@@ -44,6 +47,7 @@ let run conf =
         ~json_defaults_old:conf.json_defaults_old
         ~json_defaults_new:conf.json_defaults_new
         ~output_format:conf.output_format
+        ~with_locations:conf.with_locations
         conf.old_file conf.new_file in
     let exit_code, data =
       match out_data with
@@ -166,6 +170,24 @@ let output_format_term : Atddiff.output_format Term.t =
                                 "json", Atddiff.JSON])
                Atddiff.Text info)
 
+let no_locations_term : bool Term.t =
+  let info =
+    Arg.info ["no-locations"]
+      ~doc:"[EXPERIMENTAL] \
+            Omit file/line/column information when printing findings. \
+            This is intended for maximizing the stability of the atddiff \
+            reports so that diffing successive reports gives meaningful \
+            results. This causes the results to be sorted by hash rather \
+            than by location. The hex hash of each result is shown in both \
+            text and JSON output. It is guaranteed to be the same for \
+            a given version of atddiff compiled with a given version of \
+            OCaml. In practice, it is not expected to change \
+            often and can be used to track findings over time. Distinct \
+            findings will have the same hash if they have \
+            the same error message up to location."
+  in
+  Arg.value (Arg.flag info)
+
 let exit_success_term : bool Term.t =
   let info =
     Arg.info ["exit-success"]
@@ -228,7 +250,7 @@ let cmdline_term run =
       old_file new_file out_file
       backward forward types
       json_defaults json_defaults_old json_defaults_new
-      output_format
+      output_format no_locations
       exit_success version =
     let filter =
       let module A = Atddiff in
@@ -256,6 +278,7 @@ let cmdline_term run =
       json_defaults_old;
       json_defaults_new;
       output_format;
+      with_locations = not no_locations;
       exit_success;
       version;
     }
@@ -271,19 +294,25 @@ let cmdline_term run =
         $ json_defaults_old_term
         $ json_defaults_new_term
         $ output_format_term
+        $ no_locations_term
         $ exit_success_term
         $ version_term
        )
 
 let parse_command_line_and_run run =
-  let info =
-    Cmd.info
-      ~doc
-      ~exits:exit_info
-      ~man
-      "atddiff"
-  in
-  Cmd.v info (cmdline_term run) |> Cmd.eval |> exit
+  match Sys.argv with
+  (* gross, but avoids complaints about missing input files *)
+  | [| _; "--version" |] ->
+      print_version_and_exit ()
+  | _ ->
+      let info =
+        Cmd.info
+          ~doc
+          ~exits:exit_info
+          ~man
+          "atddiff"
+      in
+      Cmd.v info (cmdline_term run) |> Cmd.eval |> exit
 
 let safe_run conf =
   try run conf
diff --git a/atddiff/src/lib/Atddiff.ml b/atddiff/src/lib/Atddiff.ml
index 836a137..97eb411 100644
--- a/atddiff/src/lib/Atddiff.ml
+++ b/atddiff/src/lib/Atddiff.ml
@@ -19,7 +19,7 @@ type output_format = Text | JSON
 
 let version = Version.version
 
-let rec select_finding filter (x : T.full_finding) =
+let rec select_finding filter (x : T.finding) =
   match filter with
   | Or filters ->
       List.exists (fun filter -> select_finding filter x) filters
@@ -30,12 +30,12 @@ let rec select_finding filter (x : T.full_finding) =
   | Filter (Affected_type_name name) ->
       List.mem name x.affected_types
   | Filter Backward ->
-      (match x.finding.direction with
+      (match x.direction with
        | Backward | Both -> true
        | Forward -> false
       )
   | Filter Forward ->
-      (match x.finding.direction with
+      (match x.direction with
        | Forward | Both -> true
        | Backward -> false
       )
@@ -45,6 +45,7 @@ let compare_files
   ?(json_defaults_old = false)
   ?(json_defaults_new = false)
   ?(output_format = Text)
+  ?(with_locations = true)
     old_file new_file =
   let load_file atd_file =
     atd_file
@@ -59,7 +60,8 @@ let compare_files
   let res =
     let options : Compare.options = {
       json_defaults_old;
-      json_defaults_new
+      json_defaults_new;
+      sort_by = (if with_locations then Location else Hash);
     } in
     Compare.asts options ast1 ast2
   in
@@ -70,6 +72,6 @@ let compare_files
         { findings = List.filter (select_finding filter) findings } in
       Error (
         match output_format with
-        | Text -> Format_text.to_string res
-        | JSON -> Format_JSON.to_string res ^ "\n"
+        | Text -> Format_text.to_string ~with_locations res
+        | JSON -> Format_JSON.to_string ~with_locations res ^ "\n"
       )
diff --git a/atddiff/src/lib/Atddiff.mli b/atddiff/src/lib/Atddiff.mli
index dddf5d4..27b08e7 100644
--- a/atddiff/src/lib/Atddiff.mli
+++ b/atddiff/src/lib/Atddiff.mli
@@ -40,6 +40,7 @@ val compare_files :
   ?json_defaults_old:bool ->
   ?json_defaults_new:bool ->
   ?output_format:output_format ->
+  ?with_locations:bool ->
   string -> string -> (unit, string) Result.t
 
 (* Version of the atddiff library and executable *)
diff --git a/atddiff/src/lib/Atddiff_output.atd b/atddiff/src/lib/Atddiff_output.atd
index 227f20c..28580bf 100644
--- a/atddiff/src/lib/Atddiff_output.atd
+++ b/atddiff/src/lib/Atddiff_output.atd
@@ -76,6 +76,11 @@ type incompatibility_kind = [
      different findings at the same location(s).
 *)
 type finding = {
+  (* A hexadecimal hash of all the other fields excluding location fields.
+     It is not necessarily unique but should be unique in most cases.
+     It's used for sorting, tracking, and referring to findings. *)
+  hash: string;
+
   direction: direction;
   kind: incompatibility_kind;
   location_old: location option;
@@ -84,10 +89,7 @@ type finding = {
   (* The description should not mention the affected root type definition
      so as to allow the deduplication of findings. *)
   description: string;
-}
 
-type full_finding = {
-  finding: finding;
   affected_types: string list;
 }
 
@@ -95,5 +97,5 @@ type full_finding = {
    A result is a list of unique findings.
 *)
 type result = {
-  findings: full_finding list;
+  findings: finding list;
 }
diff --git a/atddiff/src/lib/Atddiff_output_t.ml b/atddiff/src/lib/Atddiff_output_t.ml
index c096bd9..fbb2bbe 100644
--- a/atddiff/src/lib/Atddiff_output_t.ml
+++ b/atddiff/src/lib/Atddiff_output_t.ml
@@ -22,13 +22,13 @@ type incompatibility_kind =
 type direction =  Backward | Forward | Both 
 
 type finding = {
+  hash: string;
   direction: direction;
   kind: incompatibility_kind;
   location_old: location option;
   location_new: location option;
-  description: string
+  description: string;
+  affected_types: string list
 }
 
-type full_finding = { finding: finding; affected_types: string list }
-
-type result = { findings: full_finding list }
+type result = { findings: finding list }
diff --git a/atddiff/src/lib/Atddiff_output_t.mli b/atddiff/src/lib/Atddiff_output_t.mli
index c096bd9..fbb2bbe 100644
--- a/atddiff/src/lib/Atddiff_output_t.mli
+++ b/atddiff/src/lib/Atddiff_output_t.mli
@@ -22,13 +22,13 @@ type incompatibility_kind =
 type direction =  Backward | Forward | Both 
 
 type finding = {
+  hash: string;
   direction: direction;
   kind: incompatibility_kind;
   location_old: location option;
   location_new: location option;
-  description: string
+  description: string;
+  affected_types: string list
 }
 
-type full_finding = { finding: finding; affected_types: string list }
-
-type result = { findings: full_finding list }
+type result = { findings: finding list }
diff --git a/atddiff/src/lib/Compare.ml b/atddiff/src/lib/Compare.ml
index 75b8feb..5e4f665 100644
--- a/atddiff/src/lib/Compare.ml
+++ b/atddiff/src/lib/Compare.ml
@@ -39,11 +39,14 @@ module Strings = Set.Make(String)
 (* This is used for instanciating type variables. *)
 module Env = Map.Make(String)
 
+type sort_by = Location | Hash
+
 type options = {
   (* Are fields with defaults always populated in old JSON data? *)
   json_defaults_old : bool;
   (* Are fields with defaults always populated in new JSON data? *)
   json_defaults_new : bool;
+  sort_by: sort_by;
 }
 
 let is_builtin_name =
@@ -94,18 +97,43 @@ let split_types types1 types2 =
   let b = Strings.of_list types2 in
   Strings.diff a b, Strings.inter a b, Strings.diff b a
 
+let create_finding
+    ~direction ~kind ?location_old ?location_new ~description () =
+  {
+    hash = ""; (* computed later *)
+    direction;
+    kind;
+    location_old;
+    location_new;
+    description;
+    affected_types = []; (* computed later *)
+  }
+
+let complete_finding (x : finding) ~affected_types =
+  let x = { x with affected_types } in
+  let hash =
+    (* Make the hash function use all the data by using very large
+       parameters *)
+    Hashtbl.hash_param 1_000_000 1_000_000
+      (x.direction, x.kind, x.description, x.affected_types)
+    |> Printf.sprintf "%08x"
+  in
+  { x with hash }
+
 let report_deleted_types defs name_set =
   List.filter_map (fun (loc, (name, _param, _an), _expr) ->
     if Strings.mem name name_set then
-      Some (([name], []), {
-        direction = Backward;
-        kind = Deleted_type;
-        location_old = Some (loc |> Loc.of_atd_loc);
-        location_new = None;
-        description =
-          sprintf "The definition for type '%s' no longer exists."
-            name
-      })
+      Some (([name], []),
+            create_finding
+              ~direction:Backward
+              ~kind:Deleted_type
+              ~location_old: (loc |> Loc.of_atd_loc)
+              ~description:(
+                sprintf "The definition for type '%s' no longer exists."
+                   name
+              )
+              ()
+           )
     else
       None
   ) defs
@@ -113,13 +141,14 @@ let report_deleted_types defs name_set =
 let report_added_types defs name_set =
   List.filter_map (fun (loc, (name, _param, _an), _expr) ->
     if Strings.mem name name_set then
-      Some (([], [name]), {
-        direction = Forward;
-        kind = Deleted_type;
-        location_old = None;
-        location_new = Some (loc |> Loc.of_atd_loc);
-        description = sprintf "There is a new type named '%s'." name
-      })
+      Some (([], [name]),
+            create_finding
+              ~direction:Forward
+              ~kind:Deleted_type
+              ~location_new:(loc |> Loc.of_atd_loc)
+              ~description:(sprintf "There is a new type named '%s'." name)
+              ()
+           )
     else
       None
   ) defs
@@ -333,8 +362,18 @@ let report_structural_mismatches options def_tbl1 def_tbl2 shared_types :
       let key = (def_name, e1, e2) in
       Hashtbl.replace visited_tbl key ()
     in
-    let add stacks x =
-      findings := (stacks, x) :: !findings in
+    let add
+        ~direction ~kind ?location_old ?location_new ~description stacks =
+      let finding =
+        create_finding
+          ~direction
+          ~kind
+          ?location_old
+          ?location_new
+          ~description
+          ()
+      in
+      findings := (stacks, finding) :: !findings in
     (*
        'stacks' is the pair of stacks of type names visited starting from
        the root definition. They're the type names affected by the finding.
@@ -365,16 +404,16 @@ let report_structural_mismatches options def_tbl1 def_tbl2 shared_types :
       | Name (_, (loc1, name1, args1), _an1),
         Name (_, (loc2, name2, args2), _an2) ->
           if name1 <> name2 then
-            add stacks {
-              direction = Both;
-              kind = Incompatible_type;
-              location_old = Some (loc1 |> Loc.of_atd_loc);
-              location_new = Some (loc2 |> Loc.of_atd_loc);
-              description =
+            add stacks
+              ~direction:Both
+              ~kind:Incompatible_type
+              ~location_old:(loc1 |> Loc.of_atd_loc)
+              ~location_new:(loc2 |> Loc.of_atd_loc)
+              ~description:(
                 sprintf "Type names '%s' and '%s' are not the same and \
                          may not be compatible."
-                  name1 name2;
-            }
+                  name1 name2
+              )
           else
             ()
       | Wrap _, _ | _, Wrap _ -> assert false
@@ -382,14 +421,14 @@ let report_structural_mismatches options def_tbl1 def_tbl2 shared_types :
           (* Type variables were normalized so they can be compared
              directly. *)
           if var1 <> var2 then
-            add stacks {
-              direction = Both;
-              kind = Incompatible_type;
-              location_old = Some (loc1 |> Loc.of_atd_loc);
-              location_new = Some (loc2 |> Loc.of_atd_loc);
-              description =
+            add stacks
+              ~direction:Both
+              ~kind:Incompatible_type
+              ~location_old:(loc1 |> Loc.of_atd_loc)
+              ~location_new:(loc2 |> Loc.of_atd_loc)
+              ~description:(
                 sprintf "Incompatible type variables are being used.";
-            }
+              )
       | (Sum _
         | Record _
         | Tuple _
@@ -399,15 +438,15 @@ let report_structural_mismatches options def_tbl1 def_tbl2 shared_types :
         | Shared _
         | Name _
         | Tvar _) as e1, e2 ->
-          add stacks {
-            direction = Both;
-            kind = Incompatible_type;
-            location_old = Some (A.loc_of_type_expr e1 |> Loc.of_atd_loc);
-            location_new = Some (A.loc_of_type_expr e2 |> Loc.of_atd_loc);
-            description =
+          add stacks
+            ~direction:Both
+            ~kind:Incompatible_type
+            ~location_old:(A.loc_of_type_expr e1 |> Loc.of_atd_loc)
+            ~location_new:(A.loc_of_type_expr e2 |> Loc.of_atd_loc)
+            ~description:(
               sprintf "Incompatible kinds of types: %s is now %s."
-                (kind_of_expr e1) (a_kind_of_expr e2);
-          }
+                (kind_of_expr e1) (a_kind_of_expr e2)
+            )
     and cmp_variants stacks loc1 loc2 cases1 cases2 =
       let with_names cases =
         cases
@@ -429,24 +468,20 @@ let report_structural_mismatches options def_tbl1 def_tbl2 shared_types :
       left_only
       |> List.iter (fun json_name ->
         let loc, (_name, _an), _opt_e = List.assoc json_name named1 in
-        add stacks {
-          direction = Backward;
-          kind = Missing_variant { variant_name = json_name };
-          location_old = Some (loc |> Loc.of_atd_loc);
-          location_new = None;
-          description = sprintf "Case '%s' disappeared." json_name
-        }
+        add stacks
+          ~direction:Backward
+          ~kind:(Missing_variant { variant_name = json_name })
+          ~location_old:(loc |> Loc.of_atd_loc)
+          ~description:(sprintf "Case '%s' disappeared." json_name)
       );
       right_only
       |> List.iter (fun json_name ->
         let loc, (_name, _an), _opt_e = List.assoc json_name named2 in
-        add stacks {
-          direction = Forward;
-          kind = Missing_variant { variant_name = json_name };
-          location_old = None;
-          location_new = Some (loc |> Loc.of_atd_loc);
-          description = sprintf "Case '%s' is new." json_name
-        }
+        add stacks
+          ~direction:Forward
+          ~kind:(Missing_variant { variant_name = json_name })
+          ~location_new:(loc |> Loc.of_atd_loc)
+          ~description:(sprintf "Case '%s' is new." json_name)
       );
       shared
       |> List.iter (fun json_name ->
@@ -457,23 +492,23 @@ let report_structural_mismatches options def_tbl1 def_tbl2 shared_types :
         | Some e1, Some e2 ->
             cmp_expr stacks e1 e2
         | Some _, None ->
-            add stacks {
-              direction = Both;
-              kind = Missing_variant_argument { variant_name = json_name };
-              location_old = Some (loc1 |> Loc.of_atd_loc);
-              location_new = Some (loc2 |> Loc.of_atd_loc);
-              description =
+            add stacks
+              ~direction:Both
+              ~kind:(Missing_variant_argument { variant_name = json_name })
+              ~location_old:(loc1 |> Loc.of_atd_loc)
+              ~location_new:(loc2 |> Loc.of_atd_loc)
+              ~description:(
                 sprintf "Case '%s' no longer has an argument." json_name
-            }
+              )
         | None, Some _ ->
-            add stacks {
-              direction = Both;
-              kind = Missing_variant_argument { variant_name = json_name };
-              location_old = Some (loc1 |> Loc.of_atd_loc);
-              location_new = Some (loc2 |> Loc.of_atd_loc);
-              description =
+            add stacks
+              ~direction:Both
+              ~kind:(Missing_variant_argument { variant_name = json_name })
+              ~location_old:(loc1 |> Loc.of_atd_loc)
+              ~location_new:(loc2 |> Loc.of_atd_loc)
+              ~description:(
                 sprintf "Case '%s' used to not have an argument." json_name
-            }
+              )
       )
     and cmp_fields stacks loc1 loc2 fields1 fields2 =
       let with_names fields =
@@ -500,13 +535,13 @@ let report_structural_mismatches options def_tbl1 def_tbl2 shared_types :
         | Optional
         | With_default -> ()
         | Required ->
-            add stacks {
-              direction = Forward;
-              kind = Missing_field { field_name = json_name };
-              location_old = Some (loc |> Loc.of_atd_loc);
-              location_new = None;
-              description = sprintf "Required field '%s' disappeared." json_name
-            }
+            add stacks
+              ~direction:Forward
+              ~kind:(Missing_field { field_name = json_name })
+              ~location_old:(loc |> Loc.of_atd_loc)
+              ~description:(
+                sprintf "Required field '%s' disappeared." json_name
+              )
       );
       right_only
       |> List.iter (fun json_name ->
@@ -515,13 +550,13 @@ let report_structural_mismatches options def_tbl1 def_tbl2 shared_types :
         | Optional
         | With_default -> ()
         | Required ->
-            add stacks {
-              direction = Backward;
-              kind = Missing_field { field_name = json_name };
-              location_old = None;
-              location_new = Some (loc |> Loc.of_atd_loc);
-              description = sprintf "Required field '%s' is new." json_name
-            }
+            add stacks
+              ~direction:Backward
+              ~kind:(Missing_field { field_name = json_name })
+              ~location_new:(loc |> Loc.of_atd_loc)
+              ~description:(
+                sprintf "Required field '%s' is new." json_name
+              )
       );
       shared
       |> List.iter (fun json_name ->
@@ -537,57 +572,57 @@ let report_structural_mismatches options def_tbl1 def_tbl2 shared_types :
          | Required, With_default
            when options.json_defaults_new -> ()
          | Required, With_default ->
-             add stacks {
-              direction = Forward;
-              kind = Default_required { field_name = json_name };
-              location_old = Some (loc1 |> Loc.of_atd_loc);
-              location_new = Some (loc2 |> Loc.of_atd_loc);
-              description =
-                sprintf "\
+             add stacks
+               ~direction:Forward
+               ~kind:(Default_required { field_name = json_name })
+               ~location_old:(loc1 |> Loc.of_atd_loc)
+               ~location_new:(loc2 |> Loc.of_atd_loc)
+               ~description:(
+                 sprintf "\
 Formerly required field '%s' is now optional but has a default value.
 You must ensure that new implementations always populate the JSON field
 with a value (using atdgen's option -j-defaults or equivalent) so that older
 implementations can read newer data. If this is already the case, use
 'atddiff --json-defaults-new' to disable this warning."
-                  json_name
-            }
+                   json_name
+               )
          | Required, Optional ->
-             add stacks {
-              direction = Forward;
-              kind = Missing_field { field_name = json_name };
-              location_old = Some (loc1 |> Loc.of_atd_loc);
-              location_new = Some (loc2 |> Loc.of_atd_loc);
-              description =
-                sprintf "Formerly required field '%s' is now optional."
-                  json_name
-            }
+             add stacks
+               ~direction:Forward
+               ~kind:(Missing_field { field_name = json_name })
+               ~location_old:(loc1 |> Loc.of_atd_loc)
+               ~location_new:(loc2 |> Loc.of_atd_loc)
+               ~description:(
+                 sprintf "Formerly required field '%s' is now optional."
+                   json_name
+               )
          | With_default, Required
            when options.json_defaults_old -> ()
          | With_default, Required ->
-             add stacks {
-              direction = Backward;
-              kind = Default_required { field_name = json_name };
-              location_old = Some (loc1 |> Loc.of_atd_loc);
-              location_new = Some (loc2 |> Loc.of_atd_loc);
-              description =
-                sprintf "\
+             add stacks
+               ~direction:Backward
+               ~kind:(Default_required { field_name = json_name })
+               ~location_old:(loc1 |> Loc.of_atd_loc)
+               ~location_new:(loc2 |> Loc.of_atd_loc)
+               ~description:(
+                 sprintf "\
 Newly required field '%s' was optional but had a default value.
 If old implementations in use always populate the JSON field
 with a value (using atdgen's option -j-defaults or equivalent),
 then there's no problem and you should use
 'atddiff --json-defaults-old' to disable this warning."
-                  json_name
-            }
+                   json_name
+               )
          | Optional, Required ->
-             add stacks {
-              direction = Backward;
-              kind = Missing_field { field_name = json_name };
-              location_old = Some (loc1 |> Loc.of_atd_loc);
-              location_new = Some (loc2 |> Loc.of_atd_loc);
-              description =
-                sprintf "Formerly optional field '%s' is now required."
-                  json_name
-            }
+             add stacks
+               ~direction:Backward
+               ~kind:(Missing_field { field_name = json_name })
+               ~location_old:(loc1 |> Loc.of_atd_loc)
+               ~location_new:(loc2 |> Loc.of_atd_loc)
+               ~description:(
+                 sprintf "Formerly optional field '%s' is now required."
+                   json_name
+               )
         );
         cmp_expr stacks e1 e2
       )
@@ -596,13 +631,12 @@ then there's no problem and you should use
       let n1 = List.length cells1 in
       let n2 = List.length cells2 in
       if n1 <> n2 then
-        add stacks {
-          direction = Both;
-          kind = Incompatible_type;
-          location_old = Some (A.loc_of_type_expr e1 |> Loc.of_atd_loc);
-          location_new = Some (A.loc_of_type_expr e2 |> Loc.of_atd_loc);
-          description = sprintf "Incompatible tuple lengths";
-        }
+        add stacks
+          ~direction:Both
+          ~kind:Incompatible_type
+          ~location_old:(A.loc_of_type_expr e1 |> Loc.of_atd_loc)
+          ~location_new:(A.loc_of_type_expr e2 |> Loc.of_atd_loc)
+          ~description:"Incompatible tuple lengths"
       else
         List.iter2 (fun (_loc1, e1, _an1) (_loc2, e2, _an2) ->
           cmp_expr stacks e1 e2
@@ -643,7 +677,7 @@ let compare_opt_location (a : Loc.t option) (b : Loc.t option) =
    3b. Position in the new file
    4. Everything else (expected to not occur)
 *)
-let compare_findings (a : finding) (b : finding) =
+let compare_findings_by_location (a : finding) (b : finding) =
   (* sort by left-only, right-only, both *)
   let c = Int.compare (finding_group a) (finding_group b) in
   if c <> 0 then c
@@ -656,7 +690,13 @@ let compare_findings (a : finding) (b : finding) =
       if c <> 0 then c
       else Stdlib.compare a b
 
-let group_and_sort_findings xs : full_finding list =
+let compare_findings_by_hash (a : finding) (b : finding) =
+  let c = String.compare a.hash b.hash in
+  if c <> 0 then c
+  else
+    compare_findings_by_location a b
+
+let group_and_sort_findings ~sort_by xs : finding list =
   let tbl = Hashtbl.create 100 in
   xs
   |> List.iter (fun ((affected_names1, affected_names2), finding) ->
@@ -669,17 +709,25 @@ let group_and_sort_findings xs : full_finding list =
         r := (Strings.union (Strings.of_list affected_names1) acc1,
               Strings.union (Strings.of_list affected_names2) acc2)
   );
-  Hashtbl.fold (fun finding r acc ->
-    let affected_names1, affected_names2 = !r in
-    (* For now, we report old and new type names as a single list.
-       We could be more precise about equivalence between old
-       and new names. Would it help the user? *)
-    let all_affected_names = Strings.union affected_names1 affected_names2 in
-    { finding;
-      affected_types = Strings.elements all_affected_names }
-    :: acc)
-    tbl []
-  |> List.sort (fun a b -> compare_findings a.finding b.finding)
+  let findings =
+    Hashtbl.fold (fun finding r acc ->
+      let affected_names1, affected_names2 = !r in
+      (* For now, we report old and new type names as a single list.
+         We could be more precise about equivalence between old
+         and new names. Would it help the user? *)
+      let all_affected_names = Strings.union affected_names1 affected_names2 in
+      assert (finding.affected_types = []);
+      complete_finding finding
+        ~affected_types:(Strings.elements all_affected_names)
+      :: acc)
+      tbl []
+  in
+  let compare_findings =
+    match sort_by with
+    | Location -> compare_findings_by_location
+    | Hash -> compare_findings_by_hash
+  in
+  List.sort compare_findings findings
 
 (*
    Expectations:
@@ -727,6 +775,6 @@ let asts options (ast1 : A.full_module) (ast2 : A.full_module) : result =
   in
   let findings =
     findings
-    |> group_and_sort_findings
+    |> group_and_sort_findings ~sort_by:options.sort_by
   in
   { findings }
diff --git a/atddiff/src/lib/Compare.mli b/atddiff/src/lib/Compare.mli
index a2d0a27..6c88267 100644
--- a/atddiff/src/lib/Compare.mli
+++ b/atddiff/src/lib/Compare.mli
@@ -4,11 +4,14 @@
    The findings are sorted nicely.
 *)
 
+type sort_by = Location | Hash
+
 type options = {
   (* Are fields with defaults always populated in old JSON data? *)
   json_defaults_old : bool;
   (* Are fields with defaults always populated in new JSON data? *)
   json_defaults_new : bool;
+  sort_by: sort_by;
 }
 
 val asts :
diff --git a/atddiff/src/lib/Format_JSON.ml b/atddiff/src/lib/Format_JSON.ml
index ceaf5a1..cd1a468 100644
--- a/atddiff/src/lib/Format_JSON.ml
+++ b/atddiff/src/lib/Format_JSON.ml
@@ -51,28 +51,29 @@ let fmt_location (x : location) : json =
     "end", fmt_position x.end_;
   ]
 
-let fmt_finding (x : finding) : json =
+let fmt_finding ~with_locations (x : finding) : json =
+  let x =
+    if with_locations then x
+    else
+      { x with location_old = None; location_new = None }
+  in
   `Assoc (remove_null_fields [
+    "hash", `String x.hash;
     "direction", fmt_direction x.direction;
     "kind", fmt_kind x.kind;
     "location_old", option fmt_location x.location_old;
     "location_new", option fmt_location x.location_new;
     "description", `String x.description;
-  ])
-
-let fmt_full_finding (x : full_finding) : json =
-  `Assoc [
-    "finding", fmt_finding x.finding;
     "affected_types", `List (List.map string x.affected_types);
-  ]
+  ])
 
-let to_yojson (x : result) : json =
+let to_yojson ~with_locations (x : result) : json =
   `Assoc [
-    "findings", `List (List.map fmt_full_finding x.findings)
+    "findings", `List (List.map (fmt_finding ~with_locations) x.findings)
   ]
 
-let to_string x =
+let to_string ~with_locations x =
   x
-  |> to_yojson
+  |> to_yojson ~with_locations
   |> Yojson.Safe.to_string
   |> Yojson.Safe.prettify
diff --git a/atddiff/src/lib/Format_JSON.mli b/atddiff/src/lib/Format_JSON.mli
index 360d12e..d7ca9e6 100644
--- a/atddiff/src/lib/Format_JSON.mli
+++ b/atddiff/src/lib/Format_JSON.mli
@@ -2,4 +2,6 @@
    Convert (tediously) the atddiff findings to JSON.
 *)
 
-val to_string : Atddiff_output_t.result -> string
+val to_string :
+  with_locations:bool ->
+  Atddiff_output_t.result -> string
diff --git a/atddiff/src/lib/Format_text.ml b/atddiff/src/lib/Format_text.ml
index 53da6f9..0432b33 100644
--- a/atddiff/src/lib/Format_text.ml
+++ b/atddiff/src/lib/Format_text.ml
@@ -15,8 +15,7 @@ let format_loc_text opt_loc1 opt_loc2 =
         (Loc.to_string loc1)
         (Loc.to_string loc2)
 
-let format_incompatibility_text buf (x : T.full_finding) =
-  let finding = x.finding in
+let format_incompatibility_text ~with_locations buf (finding : T.finding) =
   let is_certain =
     (* TODO: more clearly distinguish Warning from Error? *)
     match finding.kind with
@@ -37,23 +36,23 @@ let format_incompatibility_text buf (x : T.full_finding) =
     | Backward, false -> "Possible backward incompatibility"
     | Both, false -> "Possible forward and backward incompatibility"
   in
+  bprintf buf "[%s] %s:\n" finding.hash dir;
+  if with_locations then
+    bprintf buf "%s:\n"
+      (format_loc_text finding.location_old finding.location_new);
   bprintf buf "\
-%s:
-%s:
 %s
 The following types are affected:%s
 "
-    dir
-    (format_loc_text finding.location_old finding.location_new)
     finding.description
-    (x.affected_types
+    (finding.affected_types
      |> List.map (fun name -> "\n  " ^ name)
      |> String.concat "")
 
-let to_string (res : T.result) : string =
+let to_string ~with_locations (res : T.result) : string =
   let buf = Buffer.create 1000 in
   List.iter (fun x ->
-    format_incompatibility_text buf x;
+    format_incompatibility_text ~with_locations buf x;
     Buffer.add_char buf '\n'
   ) res.findings;
   Buffer.contents buf
diff --git a/atddiff/src/lib/Format_text.mli b/atddiff/src/lib/Format_text.mli
index 4467723..6310fc2 100644
--- a/atddiff/src/lib/Format_text.mli
+++ b/atddiff/src/lib/Format_text.mli
@@ -2,4 +2,6 @@
    Format comparison results in a human-readable form
 *)
 
-val to_string : Atddiff_output_t.result -> string
+val to_string :
+  with_locations:bool ->
+  Atddiff_output_t.result -> string
diff --git a/atddiff/src/lib/Version.ml b/atddiff/src/lib/Version.ml
index ab1c248..ba7c4aa 100644
--- a/atddiff/src/lib/Version.ml
+++ b/atddiff/src/lib/Version.ml
@@ -1,3 +1,3 @@
 (* The version string is replaced by the actual version at release time
    by 'dune release'. *)
-let version = "2.14.1"
+let version = "2.15.0"
diff --git a/atddiff/test/default/backward_incompatible_record.expected.txt b/atddiff/test/default/backward_incompatible_record.expected.txt
index bbdc3d4..dc2af28 100644
--- a/atddiff/test/default/backward_incompatible_record.expected.txt
+++ b/atddiff/test/default/backward_incompatible_record.expected.txt
@@ -1,10 +1,10 @@
-Backward incompatibility:
+[2283db51] Backward incompatibility:
 File "backward_incompatible_record_new.atd", line 2, characters 2-18:
 Required field 'added_field' is new.
 The following types are affected:
   backward_incompatible_record
 
-Backward incompatibility:
+[3c1ae3e6] Backward incompatibility:
 File "backward_incompatible_record_old.atd", line 2, characters 2-31
 File "backward_incompatible_record_new.atd", line 3, characters 2-23:
 Formerly optional field 'becomes_required' is now required.
diff --git a/atddiff/test/default/backward_incompatible_record_if_implicit_defaults.expected.txt b/atddiff/test/default/backward_incompatible_record_if_implicit_defaults.expected.txt
index 12d75a8..540b391 100644
--- a/atddiff/test/default/backward_incompatible_record_if_implicit_defaults.expected.txt
+++ b/atddiff/test/default/backward_incompatible_record_if_implicit_defaults.expected.txt
@@ -1,4 +1,4 @@
-Possible backward incompatibility:
+[1963da34] Possible backward incompatibility:
 File "backward_incompatible_record_if_implicit_defaults_old.atd", line 2, characters 2-24
 File "backward_incompatible_record_if_implicit_defaults_new.atd", line 2, characters 2-23:
 Newly required field 'becomes_required' was optional but had a default value.
diff --git a/atddiff/test/default/backward_incompatible_variant.expected.txt b/atddiff/test/default/backward_incompatible_variant.expected.txt
index e955fd8..9b11357 100644
--- a/atddiff/test/default/backward_incompatible_variant.expected.txt
+++ b/atddiff/test/default/backward_incompatible_variant.expected.txt
@@ -1,4 +1,4 @@
-Backward incompatibility:
+[2e6e3829] Backward incompatibility:
 File "backward_incompatible_variant_old.atd", line 1, characters 43-44:
 Case 'B' disappeared.
 The following types are affected:
diff --git a/atddiff/test/default/changed_renamed.expected.txt b/atddiff/test/default/changed_renamed.expected.txt
index 4198137..2544056 100644
--- a/atddiff/test/default/changed_renamed.expected.txt
+++ b/atddiff/test/default/changed_renamed.expected.txt
@@ -1,4 +1,4 @@
-Incompatibility in both directions:
+[214e5646] Incompatibility in both directions:
 File "changed_renamed_old.atd", line 10, characters 22-26
 File "changed_renamed_new.atd", line 10, characters 22-28:
 Type names 'int' and 'float' are not the same and may not be compatible.
diff --git a/atddiff/test/default/dune b/atddiff/test/default/dune
index 5ce778b..a8b118c 100644
--- a/atddiff/test/default/dune
+++ b/atddiff/test/default/dune
@@ -3,7 +3,7 @@
 (rule
  (targets backward_incompatible_record_if_implicit_defaults.txt)
  (deps backward_incompatible_record_if_implicit_defaults_old.atd backward_incompatible_record_if_implicit_defaults_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -13,7 +13,7 @@
 (rule
  (targets backward_incompatible_record.txt)
  (deps backward_incompatible_record_old.atd backward_incompatible_record_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -23,7 +23,7 @@
 (rule
  (targets backward_incompatible_variant.txt)
  (deps backward_incompatible_variant_old.atd backward_incompatible_variant_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -33,7 +33,7 @@
 (rule
  (targets changed_renamed.txt)
  (deps changed_renamed_old.atd changed_renamed_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -43,7 +43,7 @@
 (rule
  (targets forward_incompatible_record_if_implicit_defaults.txt)
  (deps forward_incompatible_record_if_implicit_defaults_old.atd forward_incompatible_record_if_implicit_defaults_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -53,7 +53,7 @@
 (rule
  (targets forward_incompatible_record.txt)
  (deps forward_incompatible_record_old.atd forward_incompatible_record_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -63,7 +63,7 @@
 (rule
  (targets forward_incompatible_variant.txt)
  (deps forward_incompatible_variant_old.atd forward_incompatible_variant_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -73,7 +73,7 @@
 (rule
  (targets ignored_type_parameters_are_ok.txt)
  (deps ignored_type_parameters_are_ok_old.atd ignored_type_parameters_are_ok_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -83,7 +83,7 @@
 (rule
  (targets json_field_name_change.txt)
  (deps json_field_name_change_old.atd json_field_name_change_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -93,7 +93,7 @@
 (rule
  (targets json_repr_change.txt)
  (deps json_repr_change_old.atd json_repr_change_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -103,7 +103,7 @@
 (rule
  (targets json_variant_name_change.txt)
  (deps json_variant_name_change_old.atd json_variant_name_change_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -113,7 +113,7 @@
 (rule
  (targets recursive.txt)
  (deps recursive_old.atd recursive_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -123,7 +123,7 @@
 (rule
  (targets recursive_types.txt)
  (deps recursive_types_old.atd recursive_types_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -133,7 +133,7 @@
 (rule
  (targets swapped_type_parameters.txt)
  (deps swapped_type_parameters_old.atd swapped_type_parameters_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -143,7 +143,7 @@
 (rule
  (targets type_arity_change.txt)
  (deps type_arity_change_old.atd type_arity_change_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -153,7 +153,7 @@
 (rule
  (targets type_name_change.txt)
  (deps type_name_change_old.atd type_name_change_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -163,7 +163,7 @@
 (rule
  (targets unchanged.txt)
  (deps unchanged_old.atd unchanged_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
@@ -173,7 +173,7 @@
 (rule
  (targets unchanged_renamed_nonroot_type.txt)
  (deps unchanged_renamed_nonroot_type_old.atd unchanged_renamed_nonroot_type_new.atd)
- (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success)))
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success )))
 
 (rule
  (alias runtest)
diff --git a/atddiff/test/default/forward_incompatible_record.expected.txt b/atddiff/test/default/forward_incompatible_record.expected.txt
index 893bd50..59f76c1 100644
--- a/atddiff/test/default/forward_incompatible_record.expected.txt
+++ b/atddiff/test/default/forward_incompatible_record.expected.txt
@@ -1,10 +1,10 @@
-Forward incompatibility:
+[381a0845] Forward incompatibility:
 File "forward_incompatible_record_old.atd", line 2, characters 2-20:
 Required field 'removed_field' disappeared.
 The following types are affected:
   forward_incompatible_record
 
-Forward incompatibility:
+[06b4c346] Forward incompatibility:
 File "forward_incompatible_record_old.atd", line 3, characters 2-23
 File "forward_incompatible_record_new.atd", line 2, characters 2-31:
 Formerly required field 'becomes_optional' is now optional.
diff --git a/atddiff/test/default/forward_incompatible_record_if_implicit_defaults.expected.txt b/atddiff/test/default/forward_incompatible_record_if_implicit_defaults.expected.txt
index 3e9eadb..1af5bbd 100644
--- a/atddiff/test/default/forward_incompatible_record_if_implicit_defaults.expected.txt
+++ b/atddiff/test/default/forward_incompatible_record_if_implicit_defaults.expected.txt
@@ -1,4 +1,4 @@
-Possible forward incompatibility:
+[2e39bd55] Possible forward incompatibility:
 File "forward_incompatible_record_if_implicit_defaults_old.atd", line 2, characters 2-23
 File "forward_incompatible_record_if_implicit_defaults_new.atd", line 2, characters 2-24:
 Formerly required field 'becomes_optional' is now optional but has a default value.
diff --git a/atddiff/test/default/forward_incompatible_variant.expected.txt b/atddiff/test/default/forward_incompatible_variant.expected.txt
index 2f69a8e..96f700a 100644
--- a/atddiff/test/default/forward_incompatible_variant.expected.txt
+++ b/atddiff/test/default/forward_incompatible_variant.expected.txt
@@ -1,4 +1,4 @@
-Forward incompatibility:
+[24b8e793] Forward incompatibility:
 File "forward_incompatible_variant_new.atd", line 1, characters 42-43:
 Case 'B' is new.
 The following types are affected:
diff --git a/atddiff/test/default/json_field_name_change.expected.txt b/atddiff/test/default/json_field_name_change.expected.txt
index 5375b25..7c1ed72 100644
--- a/atddiff/test/default/json_field_name_change.expected.txt
+++ b/atddiff/test/default/json_field_name_change.expected.txt
@@ -1,22 +1,22 @@
-Forward incompatibility:
+[2befd23c] Forward incompatibility:
 File "json_field_name_change_old.atd", line 2, characters 2-26:
 Required field 'a!' disappeared.
 The following types are affected:
   with_field_renames
 
-Forward incompatibility:
+[1dad2f90] Forward incompatibility:
 File "json_field_name_change_old.atd", line 3, characters 2-9:
 Required field 'b' disappeared.
 The following types are affected:
   with_field_renames
 
-Backward incompatibility:
+[0948d4d7] Backward incompatibility:
 File "json_field_name_change_new.atd", line 2, characters 2-9:
 Required field 'a' is new.
 The following types are affected:
   with_field_renames
 
-Backward incompatibility:
+[2f0c378c] Backward incompatibility:
 File "json_field_name_change_new.atd", line 3, characters 2-27:
 Required field 'bee' is new.
 The following types are affected:
diff --git a/atddiff/test/default/json_repr_change.expected.txt b/atddiff/test/default/json_repr_change.expected.txt
index faa42ba..b0e1059 100644
--- a/atddiff/test/default/json_repr_change.expected.txt
+++ b/atddiff/test/default/json_repr_change.expected.txt
@@ -1,4 +1,4 @@
-Incompatibility in both directions:
+[0667c515] Incompatibility in both directions:
 File "json_repr_change_old.atd", line 2, characters 21-40
 File "json_repr_change_new.atd", line 2, characters 21-61:
 Incompatible kinds of types: list/array is now a map.
diff --git a/atddiff/test/default/json_variant_name_change.expected.txt b/atddiff/test/default/json_variant_name_change.expected.txt
index ad4a99f..06b0e31 100644
--- a/atddiff/test/default/json_variant_name_change.expected.txt
+++ b/atddiff/test/default/json_variant_name_change.expected.txt
@@ -1,46 +1,46 @@
-Backward incompatibility:
+[142bf58a] Backward incompatibility:
 File "json_variant_name_change_old.atd", line 2, characters 4-5:
 Case 'A' disappeared.
 The following types are affected:
   with_constructor_renames
 
-Backward incompatibility:
+[148d17a6] Backward incompatibility:
 File "json_variant_name_change_old.atd", line 3, characters 4-12:
 Case 'B' disappeared.
 The following types are affected:
   with_constructor_renames
 
-Backward incompatibility:
+[3451ab10] Backward incompatibility:
 File "json_variant_name_change_old.atd", line 4, characters 4-23:
 Case 'cee' disappeared.
 The following types are affected:
   with_constructor_renames
 
-Backward incompatibility:
+[2ee9a5f5] Backward incompatibility:
 File "json_variant_name_change_old.atd", line 5, characters 4-30:
 Case 'dee' disappeared.
 The following types are affected:
   with_constructor_renames
 
-Forward incompatibility:
+[02dc524b] Forward incompatibility:
 File "json_variant_name_change_new.atd", line 2, characters 4-22:
 Case 'a!' is new.
 The following types are affected:
   with_constructor_renames
 
-Forward incompatibility:
+[3f5c23f4] Forward incompatibility:
 File "json_variant_name_change_new.atd", line 3, characters 4-29:
 Case 'b!' is new.
 The following types are affected:
   with_constructor_renames
 
-Forward incompatibility:
+[189456fd] Forward incompatibility:
 File "json_variant_name_change_new.atd", line 4, characters 4-5:
 Case 'C' is new.
 The following types are affected:
   with_constructor_renames
 
-Forward incompatibility:
+[1da9d4ce] Forward incompatibility:
 File "json_variant_name_change_new.atd", line 5, characters 4-12:
 Case 'D' is new.
 The following types are affected:
diff --git a/atddiff/test/default/recursive.expected.txt b/atddiff/test/default/recursive.expected.txt
index 0ec0696..aa4235c 100644
--- a/atddiff/test/default/recursive.expected.txt
+++ b/atddiff/test/default/recursive.expected.txt
@@ -1,4 +1,4 @@
-Forward incompatibility:
+[0ad2992b] Forward incompatibility:
 File "recursive_new.atd", line 9, characters 52-53:
 Case 'B' is new.
 The following types are affected:
diff --git a/atddiff/test/default/swapped_type_parameters.expected.txt b/atddiff/test/default/swapped_type_parameters.expected.txt
index 264e800..4b06109 100644
--- a/atddiff/test/default/swapped_type_parameters.expected.txt
+++ b/atddiff/test/default/swapped_type_parameters.expected.txt
@@ -1,4 +1,4 @@
-Incompatibility in both directions:
+[29041e94] Incompatibility in both directions:
 File "swapped_type_parameters_old.atd", line 3, characters 0-61
 File "swapped_type_parameters_new.atd", line 3, characters 0-61:
 Incompatible type variables are being used.
diff --git a/atddiff/test/default/type_arity_change.expected.txt b/atddiff/test/default/type_arity_change.expected.txt
index 9fa1d0f..c06cf3c 100644
--- a/atddiff/test/default/type_arity_change.expected.txt
+++ b/atddiff/test/default/type_arity_change.expected.txt
@@ -1,4 +1,4 @@
-Incompatibility in both directions:
+[319de7a2] Incompatibility in both directions:
 File "type_arity_change_old.atd", line 1, characters 0-48
 File "type_arity_change_new.atd", line 1, characters 0-42:
 Incompatible type variables are being used.
diff --git a/atddiff/test/default/type_name_change.expected.txt b/atddiff/test/default/type_name_change.expected.txt
index 3980191..2f0a9d2 100644
--- a/atddiff/test/default/type_name_change.expected.txt
+++ b/atddiff/test/default/type_name_change.expected.txt
@@ -1,22 +1,22 @@
-Possible backward incompatibility:
+[20f6af79] Possible backward incompatibility:
 File "type_name_change_old.atd", line 2, characters 0-33:
 The definition for type 'old_name_for_root_type' no longer exists.
 The following types are affected:
   old_name_for_root_type
 
-Possible backward incompatibility:
+[23b8d853] Possible backward incompatibility:
 File "type_name_change_old.atd", line 5, character 0 to line 7, character 1:
 The definition for type 'old_name_for_root_type_with_changes' no longer exists.
 The following types are affected:
   old_name_for_root_type_with_changes
 
-Possible forward incompatibility:
+[3ad32ed9] Possible forward incompatibility:
 File "type_name_change_new.atd", line 2, characters 0-33:
 There is a new type named 'new_name_for_root_type'.
 The following types are affected:
   new_name_for_root_type
 
-Possible forward incompatibility:
+[1b1d2804] Possible forward incompatibility:
 File "type_name_change_new.atd", line 5, character 0 to line 7, character 1:
 There is a new type named 'new_name_for_root_type_with_changes'.
 The following types are affected:
diff --git a/atddiff/test/filter/filter.expected.txt b/atddiff/test/filter/filter.expected.txt
index 9420112..f3da6e4 100644
--- a/atddiff/test/filter/filter.expected.txt
+++ b/atddiff/test/filter/filter.expected.txt
@@ -1,4 +1,4 @@
-Incompatibility in both directions:
+[099be5a3] Incompatibility in both directions:
 File "filter_old.atd", line 7, characters 16-20
 File "filter_new.atd", line 7, characters 16-23:
 Type names 'int' and 'string' are not the same and may not be compatible.
diff --git a/atddiff/test/filter_backward/filter.expected.txt b/atddiff/test/filter_backward/filter.expected.txt
index cf55878..d04a701 100644
--- a/atddiff/test/filter_backward/filter.expected.txt
+++ b/atddiff/test/filter_backward/filter.expected.txt
@@ -1,11 +1,11 @@
-Backward incompatibility:
+[1c4525c6] Backward incompatibility:
 File "filter_new.atd", line 6, characters 2-18:
 Required field 'added_field' is new.
 The following types are affected:
   a
   b
 
-Incompatibility in both directions:
+[099be5a3] Incompatibility in both directions:
 File "filter_old.atd", line 7, characters 16-20
 File "filter_new.atd", line 7, characters 16-23:
 Type names 'int' and 'string' are not the same and may not be compatible.
diff --git a/atddiff/test/filter_forward/filter.expected.txt b/atddiff/test/filter_forward/filter.expected.txt
index d2d468d..f86ea63 100644
--- a/atddiff/test/filter_forward/filter.expected.txt
+++ b/atddiff/test/filter_forward/filter.expected.txt
@@ -1,11 +1,11 @@
-Forward incompatibility:
+[3d596659] Forward incompatibility:
 File "filter_old.atd", line 6, characters 2-20:
 Required field 'deleted_field' disappeared.
 The following types are affected:
   a
   b
 
-Incompatibility in both directions:
+[099be5a3] Incompatibility in both directions:
 File "filter_old.atd", line 7, characters 16-20
 File "filter_new.atd", line 7, characters 16-23:
 Type names 'int' and 'string' are not the same and may not be compatible.
diff --git a/atddiff/test/generate-dune-rules b/atddiff/test/generate-dune-rules
index da2a00c..569e729 100755
--- a/atddiff/test/generate-dune-rules
+++ b/atddiff/test/generate-dune-rules
@@ -53,33 +53,41 @@ folders="
   json_defaults_old
   json_defaults_new
   json_output
+  no_locations_text
+  no_locations_json
 "
 
 for folder in $folders; do
-  atddiff_options="--exit-success"
+  atddiff_options="--exit-success "
   case "$folder" in
     default)
       ;;
     filter)
-      atddiff_options="--exit-success --backward --forward --types a,b"
+      atddiff_options+="--backward --forward --types a,b"
       ;;
     filter_backward)
-      atddiff_options="--exit-success --backward"
+      atddiff_options+="--backward"
       ;;
     filter_forward)
-      atddiff_options="--exit-success --forward"
+      atddiff_options+="--forward"
       ;;
     json_defaults)
-      atddiff_options="--exit-success --json-defaults"
+      atddiff_options+="--json-defaults"
       ;;
     json_defaults_old)
-      atddiff_options="--exit-success --json-defaults-old"
+      atddiff_options+="--json-defaults-old"
       ;;
     json_defaults_new)
-      atddiff_options="--exit-success --json-defaults-new"
+      atddiff_options+="--json-defaults-new"
       ;;
     json_output)
-      atddiff_options="--exit-success --output-format json"
+      atddiff_options+="--output-format json"
+      ;;
+    no_locations_text)
+      atddiff_options+="--no-locations -f text"
+      ;;
+    no_locations_json)
+      atddiff_options+="--no-locations -f json"
       ;;
     *)
       echo "Error: Unknown atddiff command for test folder $folder" >&2
diff --git a/atddiff/test/json_defaults_new/backward_incompatible_record_if_implicit_defaults.expected.txt b/atddiff/test/json_defaults_new/backward_incompatible_record_if_implicit_defaults.expected.txt
index 12d75a8..540b391 100644
--- a/atddiff/test/json_defaults_new/backward_incompatible_record_if_implicit_defaults.expected.txt
+++ b/atddiff/test/json_defaults_new/backward_incompatible_record_if_implicit_defaults.expected.txt
@@ -1,4 +1,4 @@
-Possible backward incompatibility:
+[1963da34] Possible backward incompatibility:
 File "backward_incompatible_record_if_implicit_defaults_old.atd", line 2, characters 2-24
 File "backward_incompatible_record_if_implicit_defaults_new.atd", line 2, characters 2-23:
 Newly required field 'becomes_required' was optional but had a default value.
diff --git a/atddiff/test/json_defaults_old/forward_incompatible_record_if_implicit_defaults.expected.txt b/atddiff/test/json_defaults_old/forward_incompatible_record_if_implicit_defaults.expected.txt
index 3e9eadb..1af5bbd 100644
--- a/atddiff/test/json_defaults_old/forward_incompatible_record_if_implicit_defaults.expected.txt
+++ b/atddiff/test/json_defaults_old/forward_incompatible_record_if_implicit_defaults.expected.txt
@@ -1,4 +1,4 @@
-Possible forward incompatibility:
+[2e39bd55] Possible forward incompatibility:
 File "forward_incompatible_record_if_implicit_defaults_old.atd", line 2, characters 2-23
 File "forward_incompatible_record_if_implicit_defaults_new.atd", line 2, characters 2-24:
 Formerly required field 'becomes_optional' is now optional but has a default value.
diff --git a/atddiff/test/json_output/all_errors.expected.txt b/atddiff/test/json_output/all_errors.expected.txt
index 24eca06..02977cb 100644
--- a/atddiff/test/json_output/all_errors.expected.txt
+++ b/atddiff/test/json_output/all_errors.expected.txt
@@ -1,281 +1,256 @@
 {
   "findings": [
     {
-      "finding": {
-        "direction": "Backward",
-        "kind": "Deleted_type",
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 1, "column": 0 },
-          "end": { "path": "all_errors_old.atd", "line": 1, "column": 18 }
-        },
-        "description": "The definition for type 'deleted' no longer exists."
+      "hash": "1b6b514f",
+      "direction": "Backward",
+      "kind": "Deleted_type",
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 1, "column": 0 },
+        "end": { "path": "all_errors_old.atd", "line": 1, "column": 18 }
       },
+      "description": "The definition for type 'deleted' no longer exists.",
       "affected_types": [ "deleted" ]
     },
     {
-      "finding": {
-        "direction": "Forward",
-        "kind": [ "Missing_field", { "field_name": "deleted_field" } ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 4, "column": 2 },
-          "end": { "path": "all_errors_old.atd", "line": 4, "column": 20 }
-        },
-        "description": "Required field 'deleted_field' disappeared."
+      "hash": "158ae3ef",
+      "direction": "Forward",
+      "kind": [ "Missing_field", { "field_name": "deleted_field" } ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 4, "column": 2 },
+        "end": { "path": "all_errors_old.atd", "line": 4, "column": 20 }
       },
+      "description": "Required field 'deleted_field' disappeared.",
       "affected_types": [ "changed_record", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Forward",
-        "kind": [ "Missing_field", { "field_name": "renamed_field" } ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 9, "column": 2 },
-          "end": { "path": "all_errors_old.atd", "line": 9, "column": 20 }
-        },
-        "description": "Required field 'renamed_field' disappeared."
+      "hash": "15e4e116",
+      "direction": "Forward",
+      "kind": [ "Missing_field", { "field_name": "renamed_field" } ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 9, "column": 2 },
+        "end": { "path": "all_errors_old.atd", "line": 9, "column": 20 }
       },
+      "description": "Required field 'renamed_field' disappeared.",
       "affected_types": [ "changed_record", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Backward",
-        "kind": [ "Missing_variant", { "variant_name": "Deleted_case" } ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 13, "column": 4 },
-          "end": { "path": "all_errors_old.atd", "line": 13, "column": 16 }
-        },
-        "description": "Case 'Deleted_case' disappeared."
+      "hash": "31591865",
+      "direction": "Backward",
+      "kind": [ "Missing_variant", { "variant_name": "Deleted_case" } ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 13, "column": 4 },
+        "end": { "path": "all_errors_old.atd", "line": 13, "column": 16 }
       },
+      "description": "Case 'Deleted_case' disappeared.",
       "affected_types": [ "changed_variant", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Backward",
-        "kind": [
-          "Missing_variant", { "variant_name": "Deleted_case_with_arg" }
-        ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 14, "column": 4 },
-          "end": { "path": "all_errors_old.atd", "line": 14, "column": 35 }
-        },
-        "description": "Case 'Deleted_case_with_arg' disappeared."
+      "hash": "3d0bf6cf",
+      "direction": "Backward",
+      "kind": [
+        "Missing_variant", { "variant_name": "Deleted_case_with_arg" }
+      ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 14, "column": 4 },
+        "end": { "path": "all_errors_old.atd", "line": 14, "column": 35 }
       },
+      "description": "Case 'Deleted_case_with_arg' disappeared.",
       "affected_types": [ "changed_variant", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Forward",
-        "kind": "Deleted_type",
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 1, "column": 0 },
-          "end": { "path": "all_errors_new.atd", "line": 1, "column": 18 }
-        },
-        "description": "There is a new type named 'created'."
+      "hash": "3669ce41",
+      "direction": "Forward",
+      "kind": "Deleted_type",
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 1, "column": 0 },
+        "end": { "path": "all_errors_new.atd", "line": 1, "column": 18 }
       },
+      "description": "There is a new type named 'created'.",
       "affected_types": [ "created" ]
     },
     {
-      "finding": {
-        "direction": "Backward",
-        "kind": [ "Missing_field", { "field_name": "new_field" } ],
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 4, "column": 2 },
-          "end": { "path": "all_errors_new.atd", "line": 4, "column": 16 }
-        },
-        "description": "Required field 'new_field' is new."
+      "hash": "29c893c7",
+      "direction": "Backward",
+      "kind": [ "Missing_field", { "field_name": "new_field" } ],
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 4, "column": 2 },
+        "end": { "path": "all_errors_new.atd", "line": 4, "column": 16 }
       },
+      "description": "Required field 'new_field' is new.",
       "affected_types": [ "changed_record", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Backward",
-        "kind": [ "Missing_field", { "field_name": "RENAMED_FIELD" } ],
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 9, "column": 2 },
-          "end": { "path": "all_errors_new.atd", "line": 9, "column": 48 }
-        },
-        "description": "Required field 'RENAMED_FIELD' is new."
+      "hash": "144944d4",
+      "direction": "Backward",
+      "kind": [ "Missing_field", { "field_name": "RENAMED_FIELD" } ],
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 9, "column": 2 },
+        "end": { "path": "all_errors_new.atd", "line": 9, "column": 48 }
       },
+      "description": "Required field 'RENAMED_FIELD' is new.",
       "affected_types": [ "changed_record", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Forward",
-        "kind": [ "Missing_variant", { "variant_name": "New_case" } ],
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 13, "column": 4 },
-          "end": { "path": "all_errors_new.atd", "line": 13, "column": 12 }
-        },
-        "description": "Case 'New_case' is new."
+      "hash": "2517ca31",
+      "direction": "Forward",
+      "kind": [ "Missing_variant", { "variant_name": "New_case" } ],
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 13, "column": 4 },
+        "end": { "path": "all_errors_new.atd", "line": 13, "column": 12 }
       },
+      "description": "Case 'New_case' is new.",
       "affected_types": [ "changed_variant", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Forward",
-        "kind": [
-          "Missing_variant", { "variant_name": "New_case_with_arg" }
-        ],
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 14, "column": 4 },
-          "end": { "path": "all_errors_new.atd", "line": 14, "column": 28 }
-        },
-        "description": "Case 'New_case_with_arg' is new."
+      "hash": "17632fe1",
+      "direction": "Forward",
+      "kind": [ "Missing_variant", { "variant_name": "New_case_with_arg" } ],
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 14, "column": 4 },
+        "end": { "path": "all_errors_new.atd", "line": 14, "column": 28 }
       },
+      "description": "Case 'New_case_with_arg' is new.",
       "affected_types": [ "changed_variant", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Forward",
-        "kind": [ "Missing_field", { "field_name": "becomes_optional" } ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 5, "column": 2 },
-          "end": { "path": "all_errors_old.atd", "line": 5, "column": 23 }
-        },
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 5, "column": 2 },
-          "end": { "path": "all_errors_new.atd", "line": 5, "column": 31 }
-        },
-        "description": "Formerly required field 'becomes_optional' is now optional."
+      "hash": "3f56a184",
+      "direction": "Forward",
+      "kind": [ "Missing_field", { "field_name": "becomes_optional" } ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 5, "column": 2 },
+        "end": { "path": "all_errors_old.atd", "line": 5, "column": 23 }
       },
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 5, "column": 2 },
+        "end": { "path": "all_errors_new.atd", "line": 5, "column": 31 }
+      },
+      "description": "Formerly required field 'becomes_optional' is now optional.",
       "affected_types": [ "changed_record", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Forward",
-        "kind": [
-          "Default_required",
-          { "field_name": "becomes_optional_with_default" }
-        ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 6, "column": 2 },
-          "end": { "path": "all_errors_old.atd", "line": 6, "column": 36 }
-        },
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 6, "column": 2 },
-          "end": { "path": "all_errors_new.atd", "line": 6, "column": 37 }
-        },
-        "description": "Formerly required field 'becomes_optional_with_default' is now optional but has a default value.\nYou must ensure that new implementations always populate the JSON field\nwith a value (using atdgen's option -j-defaults or equivalent) so that older\nimplementations can read newer data. If this is already the case, use\n'atddiff --json-defaults-new' to disable this warning."
+      "hash": "190e42a9",
+      "direction": "Forward",
+      "kind": [
+        "Default_required", { "field_name": "becomes_optional_with_default" }
+      ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 6, "column": 2 },
+        "end": { "path": "all_errors_old.atd", "line": 6, "column": 36 }
+      },
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 6, "column": 2 },
+        "end": { "path": "all_errors_new.atd", "line": 6, "column": 37 }
       },
+      "description": "Formerly required field 'becomes_optional_with_default' is now optional but has a default value.\nYou must ensure that new implementations always populate the JSON field\nwith a value (using atdgen's option -j-defaults or equivalent) so that older\nimplementations can read newer data. If this is already the case, use\n'atddiff --json-defaults-new' to disable this warning.",
       "affected_types": [ "changed_record", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Backward",
-        "kind": [ "Missing_field", { "field_name": "becomes_required" } ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 7, "column": 2 },
-          "end": { "path": "all_errors_old.atd", "line": 7, "column": 31 }
-        },
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 7, "column": 2 },
-          "end": { "path": "all_errors_new.atd", "line": 7, "column": 23 }
-        },
-        "description": "Formerly optional field 'becomes_required' is now required."
+      "hash": "2483323d",
+      "direction": "Backward",
+      "kind": [ "Missing_field", { "field_name": "becomes_required" } ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 7, "column": 2 },
+        "end": { "path": "all_errors_old.atd", "line": 7, "column": 31 }
+      },
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 7, "column": 2 },
+        "end": { "path": "all_errors_new.atd", "line": 7, "column": 23 }
       },
+      "description": "Formerly optional field 'becomes_required' is now required.",
       "affected_types": [ "changed_record", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Backward",
-        "kind": [
-          "Default_required",
-          { "field_name": "with_default_becomes_required" }
-        ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 8, "column": 2 },
-          "end": { "path": "all_errors_old.atd", "line": 8, "column": 37 }
-        },
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 8, "column": 2 },
-          "end": { "path": "all_errors_new.atd", "line": 8, "column": 36 }
-        },
-        "description": "Newly required field 'with_default_becomes_required' was optional but had a default value.\nIf old implementations in use always populate the JSON field\nwith a value (using atdgen's option -j-defaults or equivalent),\nthen there's no problem and you should use\n'atddiff --json-defaults-old' to disable this warning."
+      "hash": "029d6a0f",
+      "direction": "Backward",
+      "kind": [
+        "Default_required", { "field_name": "with_default_becomes_required" }
+      ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 8, "column": 2 },
+        "end": { "path": "all_errors_old.atd", "line": 8, "column": 37 }
       },
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 8, "column": 2 },
+        "end": { "path": "all_errors_new.atd", "line": 8, "column": 36 }
+      },
+      "description": "Newly required field 'with_default_becomes_required' was optional but had a default value.\nIf old implementations in use always populate the JSON field\nwith a value (using atdgen's option -j-defaults or equivalent),\nthen there's no problem and you should use\n'atddiff --json-defaults-old' to disable this warning.",
       "affected_types": [ "changed_record", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Both",
-        "kind": [
-          "Missing_variant_argument", { "variant_name": "Added_arg" }
-        ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 15, "column": 4 },
-          "end": { "path": "all_errors_old.atd", "line": 15, "column": 13 }
-        },
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 15, "column": 4 },
-          "end": { "path": "all_errors_new.atd", "line": 15, "column": 22 }
-        },
-        "description": "Case 'Added_arg' used to not have an argument."
+      "hash": "14e1a0cb",
+      "direction": "Both",
+      "kind": [ "Missing_variant_argument", { "variant_name": "Added_arg" } ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 15, "column": 4 },
+        "end": { "path": "all_errors_old.atd", "line": 15, "column": 13 }
+      },
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 15, "column": 4 },
+        "end": { "path": "all_errors_new.atd", "line": 15, "column": 22 }
       },
+      "description": "Case 'Added_arg' used to not have an argument.",
       "affected_types": [ "changed_variant", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Both",
-        "kind": [
-          "Missing_variant_argument", { "variant_name": "Removed_arg" }
-        ],
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 16, "column": 4 },
-          "end": { "path": "all_errors_old.atd", "line": 16, "column": 22 }
-        },
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 16, "column": 4 },
-          "end": { "path": "all_errors_new.atd", "line": 16, "column": 15 }
-        },
-        "description": "Case 'Removed_arg' no longer has an argument."
+      "hash": "0e0c3d69",
+      "direction": "Both",
+      "kind": [
+        "Missing_variant_argument", { "variant_name": "Removed_arg" }
+      ],
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 16, "column": 4 },
+        "end": { "path": "all_errors_old.atd", "line": 16, "column": 22 }
       },
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 16, "column": 4 },
+        "end": { "path": "all_errors_new.atd", "line": 16, "column": 15 }
+      },
+      "description": "Case 'Removed_arg' no longer has an argument.",
       "affected_types": [ "changed_variant", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Both",
-        "kind": "Incompatible_type",
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 17, "column": 18 },
-          "end": { "path": "all_errors_old.atd", "line": 17, "column": 22 }
-        },
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 17, "column": 18 },
-          "end": { "path": "all_errors_new.atd", "line": 17, "column": 23 }
-        },
-        "description": "Type names 'int' and 'bool' are not the same and may not be compatible."
+      "hash": "01efeb01",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 17, "column": 18 },
+        "end": { "path": "all_errors_old.atd", "line": 17, "column": 22 }
+      },
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 17, "column": 18 },
+        "end": { "path": "all_errors_new.atd", "line": 17, "column": 23 }
       },
+      "description": "Type names 'int' and 'bool' are not the same and may not be compatible.",
       "affected_types": [ "changed_variant", "indirect_changes" ]
     },
     {
-      "finding": {
-        "direction": "Both",
-        "kind": "Incompatible_type",
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 26, "column": 20 },
-          "end": { "path": "all_errors_old.atd", "line": 26, "column": 60 }
-        },
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 26, "column": 20 },
-          "end": { "path": "all_errors_new.atd", "line": 26, "column": 39 }
-        },
-        "description": "Incompatible kinds of types: map is now a list/array."
+      "hash": "09d11702",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 26, "column": 20 },
+        "end": { "path": "all_errors_old.atd", "line": 26, "column": 60 }
       },
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 26, "column": 20 },
+        "end": { "path": "all_errors_new.atd", "line": 26, "column": 39 }
+      },
+      "description": "Incompatible kinds of types: map is now a list/array.",
       "affected_types": [ "changed_map1" ]
     },
     {
-      "finding": {
-        "direction": "Both",
-        "kind": "Incompatible_type",
-        "location_old": {
-          "start": { "path": "all_errors_old.atd", "line": 27, "column": 20 },
-          "end": { "path": "all_errors_old.atd", "line": 27, "column": 39 }
-        },
-        "location_new": {
-          "start": { "path": "all_errors_new.atd", "line": 27, "column": 20 },
-          "end": { "path": "all_errors_new.atd", "line": 27, "column": 60 }
-        },
-        "description": "Incompatible kinds of types: list/array is now a map."
+      "hash": "2ddece43",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "location_old": {
+        "start": { "path": "all_errors_old.atd", "line": 27, "column": 20 },
+        "end": { "path": "all_errors_old.atd", "line": 27, "column": 39 }
+      },
+      "location_new": {
+        "start": { "path": "all_errors_new.atd", "line": 27, "column": 20 },
+        "end": { "path": "all_errors_new.atd", "line": 27, "column": 60 }
       },
+      "description": "Incompatible kinds of types: list/array is now a map.",
       "affected_types": [ "changed_map2" ]
     }
   ]
diff --git a/atddiff/test/no_locations_json/dune b/atddiff/test/no_locations_json/dune
new file mode 100644
index 0000000..87367fc
--- /dev/null
+++ b/atddiff/test/no_locations_json/dune
@@ -0,0 +1,32 @@
+; Generated by ./generate-dune-rules
+; For adding tests, read the instructions in the Makefile.
+(rule
+ (targets ordering.txt)
+ (deps ordering_old.atd ordering_new.atd)
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success --no-locations -f json)))
+
+(rule
+ (alias runtest)
+ (deps ordering.txt)
+ (action (diff ordering.expected.txt ordering.txt)))
+
+(rule
+ (targets same_hash.txt)
+ (deps same_hash_old.atd same_hash_new.atd)
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success --no-locations -f json)))
+
+(rule
+ (alias runtest)
+ (deps same_hash.txt)
+ (action (diff same_hash.expected.txt same_hash.txt)))
+
+(rule
+ (targets simple.txt)
+ (deps simple_old.atd simple_new.atd)
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success --no-locations -f json)))
+
+(rule
+ (alias runtest)
+ (deps simple.txt)
+ (action (diff simple.expected.txt simple.txt)))
+
diff --git a/atddiff/test/no_locations_json/ordering.expected.txt b/atddiff/test/no_locations_json/ordering.expected.txt
new file mode 100644
index 0000000..91e9d2a
--- /dev/null
+++ b/atddiff/test/no_locations_json/ordering.expected.txt
@@ -0,0 +1,46 @@
+{
+  "findings": [
+    {
+      "hash": "0ba447bf",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "description": "Incompatible kinds of types: list/array is now a string.",
+      "affected_types": [ "e" ]
+    },
+    {
+      "hash": "1c2c4aae",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "description": "Incompatible kinds of types: tuple is now a string.",
+      "affected_types": [ "c" ]
+    },
+    {
+      "hash": "2182fd1f",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "description": "Incompatible kinds of types: list/array is now a string.",
+      "affected_types": [ "b" ]
+    },
+    {
+      "hash": "2e525f5c",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "description": "Incompatible kinds of types: list/array is now a string.",
+      "affected_types": [ "f" ]
+    },
+    {
+      "hash": "3b527108",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "description": "Incompatible kinds of types: tuple is now a string.",
+      "affected_types": [ "d" ]
+    },
+    {
+      "hash": "3f176ef7",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "description": "Type names 'int' and 'string' are not the same and may not be compatible.",
+      "affected_types": [ "a" ]
+    }
+  ]
+}
diff --git a/atddiff/test/no_locations_json/ordering_new.atd b/atddiff/test/no_locations_json/ordering_new.atd
new file mode 100644
index 0000000..e37b9df
--- /dev/null
+++ b/atddiff/test/no_locations_json/ordering_new.atd
@@ -0,0 +1,6 @@
+type a = string
+type b = string
+type c = string
+type d = string
+type e = string
+type f = string
diff --git a/atddiff/test/no_locations_json/ordering_old.atd b/atddiff/test/no_locations_json/ordering_old.atd
new file mode 100644
index 0000000..2b35677
--- /dev/null
+++ b/atddiff/test/no_locations_json/ordering_old.atd
@@ -0,0 +1,6 @@
+type a = int
+type b = int list
+type c = (b * b)
+type d = (a * b)
+type e = c list
+type f = d list
diff --git a/atddiff/test/no_locations_json/same_hash.expected.txt b/atddiff/test/no_locations_json/same_hash.expected.txt
new file mode 100644
index 0000000..f71f730
--- /dev/null
+++ b/atddiff/test/no_locations_json/same_hash.expected.txt
@@ -0,0 +1,18 @@
+{
+  "findings": [
+    {
+      "hash": "177fee07",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "description": "Type names 'int' and 'string' are not the same and may not be compatible.",
+      "affected_types": [ "t" ]
+    },
+    {
+      "hash": "177fee07",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "description": "Type names 'int' and 'string' are not the same and may not be compatible.",
+      "affected_types": [ "t" ]
+    }
+  ]
+}
diff --git a/atddiff/test/no_locations_json/same_hash_new.atd b/atddiff/test/no_locations_json/same_hash_new.atd
new file mode 100644
index 0000000..86bd5b4
--- /dev/null
+++ b/atddiff/test/no_locations_json/same_hash_new.atd
@@ -0,0 +1 @@
+type t = (string * string)
diff --git a/atddiff/test/no_locations_json/same_hash_old.atd b/atddiff/test/no_locations_json/same_hash_old.atd
new file mode 100644
index 0000000..a26d4ce
--- /dev/null
+++ b/atddiff/test/no_locations_json/same_hash_old.atd
@@ -0,0 +1,5 @@
+(*
+  This test produces two findings with the same hash ID
+*)
+
+type t = (int * int)
diff --git a/atddiff/test/no_locations_json/simple.expected.txt b/atddiff/test/no_locations_json/simple.expected.txt
new file mode 100644
index 0000000..12db515
--- /dev/null
+++ b/atddiff/test/no_locations_json/simple.expected.txt
@@ -0,0 +1,11 @@
+{
+  "findings": [
+    {
+      "hash": "177fee07",
+      "direction": "Both",
+      "kind": "Incompatible_type",
+      "description": "Type names 'int' and 'string' are not the same and may not be compatible.",
+      "affected_types": [ "t" ]
+    }
+  ]
+}
diff --git a/atddiff/test/no_locations_json/simple_new.atd b/atddiff/test/no_locations_json/simple_new.atd
new file mode 100644
index 0000000..c6a8e28
--- /dev/null
+++ b/atddiff/test/no_locations_json/simple_new.atd
@@ -0,0 +1 @@
+type t = string
diff --git a/atddiff/test/no_locations_json/simple_old.atd b/atddiff/test/no_locations_json/simple_old.atd
new file mode 100644
index 0000000..975adb5
--- /dev/null
+++ b/atddiff/test/no_locations_json/simple_old.atd
@@ -0,0 +1 @@
+type t = int
diff --git a/atddiff/test/no_locations_text/dune b/atddiff/test/no_locations_text/dune
new file mode 100644
index 0000000..27773c9
--- /dev/null
+++ b/atddiff/test/no_locations_text/dune
@@ -0,0 +1,32 @@
+; Generated by ./generate-dune-rules
+; For adding tests, read the instructions in the Makefile.
+(rule
+ (targets ordering.txt)
+ (deps ordering_old.atd ordering_new.atd)
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success --no-locations -f text)))
+
+(rule
+ (alias runtest)
+ (deps ordering.txt)
+ (action (diff ordering.expected.txt ordering.txt)))
+
+(rule
+ (targets same_hash.txt)
+ (deps same_hash_old.atd same_hash_new.atd)
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success --no-locations -f text)))
+
+(rule
+ (alias runtest)
+ (deps same_hash.txt)
+ (action (diff same_hash.expected.txt same_hash.txt)))
+
+(rule
+ (targets simple.txt)
+ (deps simple_old.atd simple_new.atd)
+ (action (run %{bin:atddiff} %{deps} -o %{targets} --exit-success --no-locations -f text)))
+
+(rule
+ (alias runtest)
+ (deps simple.txt)
+ (action (diff simple.expected.txt simple.txt)))
+
diff --git a/atddiff/test/no_locations_text/ordering.expected.txt b/atddiff/test/no_locations_text/ordering.expected.txt
new file mode 100644
index 0000000..9cf28f6
--- /dev/null
+++ b/atddiff/test/no_locations_text/ordering.expected.txt
@@ -0,0 +1,30 @@
+[0ba447bf] Incompatibility in both directions:
+Incompatible kinds of types: list/array is now a string.
+The following types are affected:
+  e
+
+[1c2c4aae] Incompatibility in both directions:
+Incompatible kinds of types: tuple is now a string.
+The following types are affected:
+  c
+
+[2182fd1f] Incompatibility in both directions:
+Incompatible kinds of types: list/array is now a string.
+The following types are affected:
+  b
+
+[2e525f5c] Incompatibility in both directions:
+Incompatible kinds of types: list/array is now a string.
+The following types are affected:
+  f
+
+[3b527108] Incompatibility in both directions:
+Incompatible kinds of types: tuple is now a string.
+The following types are affected:
+  d
+
+[3f176ef7] Incompatibility in both directions:
+Type names 'int' and 'string' are not the same and may not be compatible.
+The following types are affected:
+  a
+
diff --git a/atddiff/test/no_locations_text/ordering_new.atd b/atddiff/test/no_locations_text/ordering_new.atd
new file mode 100644
index 0000000..e37b9df
--- /dev/null
+++ b/atddiff/test/no_locations_text/ordering_new.atd
@@ -0,0 +1,6 @@
+type a = string
+type b = string
+type c = string
+type d = string
+type e = string
+type f = string
diff --git a/atddiff/test/no_locations_text/ordering_old.atd b/atddiff/test/no_locations_text/ordering_old.atd
new file mode 100644
index 0000000..2b35677
--- /dev/null
+++ b/atddiff/test/no_locations_text/ordering_old.atd
@@ -0,0 +1,6 @@
+type a = int
+type b = int list
+type c = (b * b)
+type d = (a * b)
+type e = c list
+type f = d list
diff --git a/atddiff/test/no_locations_text/same_hash.expected.txt b/atddiff/test/no_locations_text/same_hash.expected.txt
new file mode 100644
index 0000000..a0fd66a
--- /dev/null
+++ b/atddiff/test/no_locations_text/same_hash.expected.txt
@@ -0,0 +1,10 @@
+[177fee07] Incompatibility in both directions:
+Type names 'int' and 'string' are not the same and may not be compatible.
+The following types are affected:
+  t
+
+[177fee07] Incompatibility in both directions:
+Type names 'int' and 'string' are not the same and may not be compatible.
+The following types are affected:
+  t
+
diff --git a/atddiff/test/no_locations_text/same_hash_new.atd b/atddiff/test/no_locations_text/same_hash_new.atd
new file mode 100644
index 0000000..86bd5b4
--- /dev/null
+++ b/atddiff/test/no_locations_text/same_hash_new.atd
@@ -0,0 +1 @@
+type t = (string * string)
diff --git a/atddiff/test/no_locations_text/same_hash_old.atd b/atddiff/test/no_locations_text/same_hash_old.atd
new file mode 100644
index 0000000..a26d4ce
--- /dev/null
+++ b/atddiff/test/no_locations_text/same_hash_old.atd
@@ -0,0 +1,5 @@
+(*
+  This test produces two findings with the same hash ID
+*)
+
+type t = (int * int)
diff --git a/atddiff/test/no_locations_text/simple.expected.txt b/atddiff/test/no_locations_text/simple.expected.txt
new file mode 100644
index 0000000..5dfaec8
--- /dev/null
+++ b/atddiff/test/no_locations_text/simple.expected.txt
@@ -0,0 +1,5 @@
+[177fee07] Incompatibility in both directions:
+Type names 'int' and 'string' are not the same and may not be compatible.
+The following types are affected:
+  t
+
diff --git a/atddiff/test/no_locations_text/simple_new.atd b/atddiff/test/no_locations_text/simple_new.atd
new file mode 100644
index 0000000..c6a8e28
--- /dev/null
+++ b/atddiff/test/no_locations_text/simple_new.atd
@@ -0,0 +1 @@
+type t = string
diff --git a/atddiff/test/no_locations_text/simple_old.atd b/atddiff/test/no_locations_text/simple_old.atd
new file mode 100644
index 0000000..975adb5
--- /dev/null
+++ b/atddiff/test/no_locations_text/simple_old.atd
@@ -0,0 +1 @@
+type t = int
diff --git a/atddiff/test/version/dune b/atddiff/test/version/dune
new file mode 100644
index 0000000..b0de332
--- /dev/null
+++ b/atddiff/test/version/dune
@@ -0,0 +1,14 @@
+(rule
+ (targets version.txt)
+ (deps )
+ (action
+   (with-stdout-to version.txt
+     (run %{bin:atddiff} --version)
+   )
+ )
+)
+
+(rule
+ (alias runtest)
+ (deps version.txt)
+ (action (diff version.expected.txt version.txt)))
diff --git a/atddiff/test/version/version.expected.txt b/atddiff/test/version/version.expected.txt
new file mode 100644
index 0000000..68e69e4
--- /dev/null
+++ b/atddiff/test/version/version.expected.txt
@@ -0,0 +1 @@
+2.15.0
diff --git a/atdgen-codec-runtime.opam b/atdgen-codec-runtime.opam
index 74f80ea..256c507 100644
--- a/atdgen-codec-runtime.opam
+++ b/atdgen-codec-runtime.opam
@@ -1,4 +1,4 @@
-version: "2.14.1"
+version: "2.15.0"
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
 synopsis: "Runtime for atdgen generated bucklescript converters"
diff --git a/atdgen-runtime.opam b/atdgen-runtime.opam
index 74bea00..e9ff352 100644
--- a/atdgen-runtime.opam
+++ b/atdgen-runtime.opam
@@ -1,4 +1,4 @@
-version: "2.14.1"
+version: "2.15.0"
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
 synopsis: "Runtime library for code generated by atdgen"
diff --git a/atdgen-runtime/src/version.ml b/atdgen-runtime/src/version.ml
index ab1c248..ba7c4aa 100644
--- a/atdgen-runtime/src/version.ml
+++ b/atdgen-runtime/src/version.ml
@@ -1,3 +1,3 @@
 (* The version string is replaced by the actual version at release time
    by 'dune release'. *)
-let version = "2.14.1"
+let version = "2.15.0"
diff --git a/atdgen.opam b/atdgen.opam
index bbb6c45..a2f277a 100644
--- a/atdgen.opam
+++ b/atdgen.opam
@@ -1,4 +1,4 @@
-version: "2.14.1"
+version: "2.15.0"
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
 synopsis:
diff --git a/atdgen/src/deprecated/version.ml b/atdgen/src/deprecated/version.ml
index ab1c248..ba7c4aa 100644
--- a/atdgen/src/deprecated/version.ml
+++ b/atdgen/src/deprecated/version.ml
@@ -1,3 +1,3 @@
 (* The version string is replaced by the actual version at release time
    by 'dune release'. *)
-let version = "2.14.1"
+let version = "2.15.0"
diff --git a/atdgen/src/version.ml b/atdgen/src/version.ml
index ab1c248..ba7c4aa 100644
--- a/atdgen/src/version.ml
+++ b/atdgen/src/version.ml
@@ -1,3 +1,3 @@
 (* The version string is replaced by the actual version at release time
    by 'dune release'. *)
-let version = "2.14.1"
+let version = "2.15.0"
diff --git a/atdj.opam b/atdj.opam
index fd87834..de46d06 100644
--- a/atdj.opam
+++ b/atdj.opam
@@ -1,4 +1,4 @@
-version: "2.14.1"
+version: "2.15.0"
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
 synopsis: "Java code generation for ATD"
diff --git a/atdpy.opam b/atdpy.opam
index 31c89f5..4f4494e 100644
--- a/atdpy.opam
+++ b/atdpy.opam
@@ -1,4 +1,4 @@
-version: "2.14.1"
+version: "2.15.0"
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
 synopsis: "Python/mypy code generation for ATD APIs"
diff --git a/atdpy/src/lib/Version.ml b/atdpy/src/lib/Version.ml
index ab1c248..ba7c4aa 100644
--- a/atdpy/src/lib/Version.ml
+++ b/atdpy/src/lib/Version.ml
@@ -1,3 +1,3 @@
 (* The version string is replaced by the actual version at release time
    by 'dune release'. *)
-let version = "2.14.1"
+let version = "2.15.0"
diff --git a/atds.opam b/atds.opam
index 8c25f74..6896b30 100644
--- a/atds.opam
+++ b/atds.opam
@@ -1,4 +1,4 @@
-version: "2.14.1"
+version: "2.15.0"
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
 synopsis: "ATD Code generator for Scala"
diff --git a/atdts.opam b/atdts.opam
index 37ae9c4..2a6090e 100644
--- a/atdts.opam
+++ b/atdts.opam
@@ -1,4 +1,4 @@
-version: "2.14.1"
+version: "2.15.0"
 # This file is generated by dune, edit dune-project instead
 opam-version: "2.0"
 synopsis: "TypeScript code generation for ATD APIs"
diff --git a/atdts/src/lib/Version.ml b/atdts/src/lib/Version.ml
index ab1c248..ba7c4aa 100644
--- a/atdts/src/lib/Version.ml
+++ b/atdts/src/lib/Version.ml
@@ -1,3 +1,3 @@
 (* The version string is replaced by the actual version at release time
    by 'dune release'. *)
-let version = "2.14.1"
+let version = "2.15.0"
diff --git a/dune-project b/dune-project
index d6c1a69..5acec87 100644
--- a/dune-project
+++ b/dune-project
@@ -3,7 +3,7 @@
 (implicit_transitive_deps false)
 
 (name atd)
-(version 2.14.1)
+(version 2.15.0)
 (license MIT)
 
 (maintainers