[#1047] Mark headers with compiler attributes as used

apps/els_lsp/priv/code_navigation/src/diagnostics_unused_includes_compiler_attribute.erl

@@ -0,0 +1,8 @@
+%% Issue 1047
+-module(diagnostics_unused_includes_compiler_attribute).
+
+-include_lib("kernel/include/file.hrl").
+-include_lib("eunit/include/eunit.hrl").
+
+the_test() ->
+  ok.

apps/els_lsp/src/els_parser.erl

@@ -221,7 +221,12 @@ attribute(Tree) ->
           []
       end;
     {compile, [Arg]} ->
-      find_compile_options_pois(Arg);
+      %% When we encounter a compiler attribute, we include a POI
+      %% indicating the fact. This is useful, for example, to avoid
+      %% marking header files including parse transforms or other
+      %% compiler attributes as unused. See #1047
+      Marker = poi(erl_syntax:get_pos(Arg), compile, unused),
+      [Marker|find_compile_options_pois(Arg)];
     {AttrName, [Arg]} when AttrName =:= export;
                            AttrName =:= export_type ->
       find_export_pois(Tree, AttrName, Arg);

apps/els_lsp/src/els_unused_includes_diagnostics.erl

@@ -65,6 +65,7 @@ find_unused_includes(#{uri := Uri} = Document) ->
     , export_type_entry
     ]),
   IncludedUris0 = els_diagnostics_utils:included_uris(Document),
+  IncludedUris1 = filter_includes_with_compiler_attributes(IncludedUris0),
   ExcludeUnusedIncludes =
       lists:filtermap(
           fun(Include) ->
@@ -74,7 +75,7 @@ find_unused_includes(#{uri := Uri} = Document) ->
                       false
               end
           end, els_config:get(exclude_unused_includes)),
-  IncludedUris = IncludedUris0 -- ExcludeUnusedIncludes,
+  IncludedUris = IncludedUris1 -- ExcludeUnusedIncludes,
   Fun = fun(POI, Acc) ->
             update_unused(Graph, Uri, POI, Acc)
         end,
@@ -120,3 +121,31 @@ inclusion_range(Uri, Document) ->
     _ ->
       #{from => {1, 1}, to => {2, 1}}
   end.
+
+%% @doc Given a list of included uris, filter out the ones containing
+%% compiler attributes. If the Uri cannot be found, keep it in the list.
+-spec filter_includes_with_compiler_attributes([uri()]) -> [uri()].
+filter_includes_with_compiler_attributes(Uris) ->
+  Filter = fun(Uri) ->
+               case els_utils:lookup_document(Uri) of
+                 {error, _Error} ->
+                   {true, Uri};
+                 {ok, Document} ->
+                    case contains_compiler_attributes(Document) of
+                      true ->
+                        false;
+                      false ->
+                        {true, Uri}
+                    end
+               end
+           end,
+  lists:filtermap(Filter, Uris).
+
+%% @doc Return true if the Document contains a compiler attribute.
+-spec contains_compiler_attributes(els_dt_document:item()) -> boolean().
+contains_compiler_attributes(Document) ->
+  compiler_attributes(Document) =/= [].
+
+-spec compiler_attributes(els_dt_document:item()) -> [poi()].
+compiler_attributes(Document) ->
+  els_dt_document:pois(Document, [compile]).

apps/els_lsp/test/els_diagnostics_SUITE.erl

@@ -35,6 +35,7 @@
         , crossref_autoimport_disabled/1
         , crossref_pseudo_functions/1
         , unused_includes/1
+        , unused_includes_compiler_attribute/1
         , exclude_unused_includes/1
         , unused_macros/1
         ]).
@@ -369,14 +370,11 @@ compiler_with_parse_transform_included(Config) ->
   els_mock_diagnostics:subscribe(),
   ok = els_client:did_save(Uri),
   Diagnostics = els_mock_diagnostics:wait_until_complete(),
-  ?assertEqual(2, length(Diagnostics)),
+  ?assertEqual(1, length(Diagnostics)),
   Warnings = [D || #{severity := ?DIAGNOSTIC_WARNING} = D <- Diagnostics],
-  ?assertEqual(2, length(Warnings)),
+  ?assertEqual(1, length(Warnings)),
   WarningRanges = [ Range || #{range := Range} <- Warnings],
   ExpectedWarningsRanges =
-        [#{ 'end' => #{character => 32, line => 4}
-          , start => #{character => 0, line => 4}}
-        ] ++
         fixcolumns(
           [ #{ 'end' => #{character => 9, line => 6}
              , start => #{character => 5, line => 6}}], Config),
@@ -709,6 +707,28 @@ unused_includes(Config) ->
   ?assertEqual(Expected, lists:sort(F, Diagnostics)),
   ok.
 
+-spec unused_includes_compiler_attribute(config()) -> ok.
+unused_includes_compiler_attribute(Config) ->
+  Uri = ?config(diagnostics_unused_includes_compiler_attribute_uri, Config),
+  els_mock_diagnostics:subscribe(),
+  ok = els_client:did_save(Uri),
+  Diagnostics = els_mock_diagnostics:wait_until_complete(),
+  Expected = [ #{ message => <<"Unused file: file.hrl">>
+                , range =>
+                    #{ 'end' => #{ character => 40
+                                 , line => 3
+                                 }
+                     , start => #{ character => 0
+                                 , line => 3
+                                 }
+                     }
+                , severity => 2
+                , source => <<"UnusedIncludes">>
+                }
+             ],
+  ?assertEqual(Expected, Diagnostics),
+  ok.
+
 -spec exclude_unused_includes(config()) -> ok.
 exclude_unused_includes(Config) ->
   Uri = ?config(diagnostics_unused_includes_uri, Config),

apps/els_lsp/test/els_test_utils.erl

@@ -154,6 +154,7 @@ sources() ->
   , diagnostics_xref
   , diagnostics_xref_pseudo
   , diagnostics_unused_includes
+  , diagnostics_unused_includes_compiler_attribute
   , diagnostics_unused_macros
   , elvis_diagnostics
   , execute_command_suggest_spec