[Fix #1832] Add eldoc info for datomic query input parameters

1 files changed, 44 insertions, 4 deletions

diff --git a/cider-eldoc.el b/cider-eldoc.el
index b7012b46..8af59508 100644
--- a/cider-eldoc.el
+++ b/cider-eldoc.el
@@ -86,6 +86,15 @@ displayed.  When nil, always display eldoc for first symbol of the sexp."
   :group 'cider
   :package-version '(cider . "0.13.0"))
 
+(defcustom cider-eldoc-display-context-dependent-info nil
+  "When non-nil, display context dependent info in the eldoc where possible.
+CIDER will try to add expected function arguments based on the current context,
+for example for the datomic.api/q function where it will show the expected
+inputs of the query at point."
+  :type 'boolean
+  :group 'cider
+  :package-version '(cider . "0.15.0"))
+
 (defun cider--eldoc-format-class-names (class-names)
   "Return a formatted CLASS-NAMES prefix string.
 CLASS-NAMES is a list of classes to which a Java interop form belongs.
@@ -398,10 +407,23 @@ This includes the arglist and ns and symbol name (if available)."
                                         "arglists" arglists
                                         "docstring" docstring
                                         "type" type)))
-                ;; middleware eldoc lookups are expensive, so we
-                ;; cache the last lookup.  This eliminates the need
-                ;; for extra middleware requests within the same sexp.
-                (setq cider-eldoc-last-symbol (list thing eldoc-plist))
+                ;; add context dependent args if requested by defcustom
+                ;; do not cache this eldoc info to avoid showing info
+                ;: of the previous context
+                (if cider-eldoc-display-context-dependent-info
+                    (cond
+                     ;; add inputs of datomic query
+                     ((and (equal ns-or-class "datomic.api")
+                           (equal name-or-member "q"))
+                      (let ((arglists (lax-plist-get eldoc-plist "arglists")))
+                        (lax-plist-put eldoc-plist "arglists"
+                                       (cider--eldoc-add-datomic-query-inputs-to-arglists arglists))))
+                     ;; if none of the clauses is successful, do cache the eldoc
+                     (t (setq cider-eldoc-last-symbol (list thing eldoc-plist))))
+                  ;; middleware eldoc lookups are expensive, so we
+                  ;; cache the last lookup.  This eliminates the need
+                  ;; for extra middleware requests within the same sexp.
+                  (setq cider-eldoc-last-symbol (list thing eldoc-plist)))
                 eldoc-plist))))))))
 
 (defun cider--eldoc-remove-dot (sym)
@@ -413,6 +435,24 @@ Only useful for interop forms.  Clojure forms would be returned unchanged."
   "Check whether FILE-NAME is representing an EDN file."
   (and file-name (equal (file-name-extension file-name) "edn")))
 
+(defun cider--eldoc-add-datomic-query-inputs-to-arglists (arglists)
+  "Add the expected inputs of the datomic query to the ARGLISTS."
+  (if (cider-second-sexp-in-list)
+    (let* ((query (cider-second-sexp-in-list))
+           (query-inputs (nrepl-dict-get
+                          (cider-sync-request:eldoc-datomic-query query)
+                          "inputs")))
+      (if query-inputs
+          (thread-first
+              (thread-last arglists
+                (car)
+                (remove "&")
+                (remove "inputs"))
+            (append (car query-inputs))
+            (list))
+        arglists))
+    arglists))
+
 (defun cider-eldoc ()
   "Backend function for eldoc to show argument list in the echo area."
   (when (and (cider-connected-p)