Detect duplicate .sitemap entries

I had several duplicate .sitemap entries, which created bizarre
problems trying to construct relative links.  Detect those and
abort when they are seen.

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/App/DocKnot/Spin/Sitemap.pm b/lib/App/DocKnot/Spin/Sitemap.pm
index f8dfcd1..ee2d4d2 100644
--- a/lib/App/DocKnot/Spin/Sitemap.pm
+++ b/lib/App/DocKnot/Spin/Sitemap.pm
@@ -38,6 +38,7 @@ use List::SomeUtils qw(pairwise);
 #         Text exception on file parsing errors
 sub _read_data {
     my ($self, $path) = @_;
+    my %seen;
 
     # @indents holds a stack of indentation levels to detect indentation
     # changes that translate into page structure.  Each element in the stack
@@ -71,6 +72,12 @@ sub _read_data {
             die "invalid line $. in $path\n";
         }
 
+        # Error on duplicate lines.
+        if ($seen{$url}) {
+            die "duplicate entry for $url in $path (line $.)\n";
+        }
+        $seen{$url} = 1;
+
         # Open or close indentation levels.
         my $indent = length($spaces);
         if (!@indents || $indent > $indents[-1]->[0]) {