Sort errors by location before appending them to the AST

This may seem like an unnecessary feature since the whole point
of embedding errors is to allow reporting them all at once. This works
with merlin but not with the compiler which will only report the first
one it encounters.

Signed-off-by: Nathan Rebours <[email protected]>

src/driver.ml

@@ -631,6 +631,12 @@ let print_passes () =
     if !perform_checks_on_extensions then
       Printf.printf "<builtin:check-unused-extensions>\n")
 
+let sort_errors_by_loc errors =
+  List.sort errors ~cmp:(fun error error' ->
+      let loc = Location.Error.get_location error in
+      let loc' = Location.Error.get_location error' in
+      Location.compare loc loc')
+
 (*$*)
 
 let map_structure_gen st ~tool_name ~hook ~expect_mismatch_handler ~input_name
@@ -652,7 +658,8 @@ let map_structure_gen st ~tool_name ~hook ~expect_mismatch_handler ~input_name
     st
   in
   let with_errors errors st =
-    List.map errors ~f:(fun error ->
+    let sorted = sort_errors_by_loc errors in
+    List.map sorted ~f:(fun error ->
         Ast_builder.Default.pstr_extension
           ~loc:(Location.Error.get_location error)
           (Location.Error.to_extension error)
@@ -727,7 +734,8 @@ let map_signature_gen sg ~tool_name ~hook ~expect_mismatch_handler ~input_name
     sg
   in
   let with_errors errors sg =
-    List.map errors ~f:(fun error ->
+    let sorted = sort_errors_by_loc errors in
+    List.map sorted ~f:(fun error ->
         Ast_builder.Default.psig_extension
           ~loc:(Location.Error.get_location error)
           (Location.Error.to_extension error)