Fix #1914

Error code of dune format should be non zero when it fails

Signed-off-by: Rudi Grinberg <rudi.grinberg@gmail.com>

CHANGES.md

@@ -33,6 +33,9 @@ correctly erased by ^K. (#1912, @aalekseyev)
 - Fix generation of `.merlin` files on Windows. `\` characters needed
   to be escaped (#1869, @mlasson)
 
+- Fix 0 error code when `$ dune format-dune-file` fails. (#1915, fix #1914,
+  @rgrinberg)
+
 1.7.3 (unreleased)
 ------------------
 

src/format_dune_lang.ml

@@ -122,9 +122,10 @@ let pp_top_sexps =
 let format_file ~input =
   match parse_file input with
   | exception Dune_lang.Parse_error e ->
-    Printf.printf
+    Printf.eprintf
       "Parse error: %s\n"
-      (Dune_lang.Parse_error.message e)
+      (Dune_lang.Parse_error.message e);
+    exit 1
   | OCaml_syntax loc ->
     Errors.warn loc "OCaml syntax is not supported, skipping."
   | Sexps sexps ->

test/blackbox-tests/test-cases/format-dune-file/run.t

@@ -36,6 +36,7 @@ Parse errors are displayed:
 
   $ echo '(' | dune format-dune-file
   Parse error: unclosed parenthesis at end of input
+  [1]
 
 When a list is indented, there is no extra space at the end.
 
@@ -153,3 +154,9 @@ Files in OCaml syntax are ignored with a warning.
   1 | (* -*- tuareg -*- *)
       ^^^^^^^^^^^^^^^^^^^^
   Warning: OCaml syntax is not supported, skipping.
+
+Non 0 error code:
+
+  $ echo "(" | dune format ; echo $?
+  Parse error: unclosed parenthesis at end of input
+  1