[#1098] Detect unused record fields

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

@@ -0,0 +1,11 @@
+-module(diagnostics_unused_record_fields).
+
+-export([main/1]).
+
+-record(used_field, {field_a, field_b = 42}).
+-record(unused_field, {field_c, field_d}).
+
+main(#used_field{field_a = A, field_b = B}) ->
+  {A, B};
+main(R) ->
+  R#unused_field.field_c.

apps/els_lsp/src/els_diagnostics.erl

@@ -64,6 +64,7 @@ available_diagnostics() ->
   , <<"elvis">>
   , <<"unused_includes">>
   , <<"unused_macros">>
+  , <<"unused_record_fields">>
   ].
 
 -spec default_diagnostics() -> [diagnostic_id()].

apps/els_lsp/src/els_unused_record_fields_diagnostics.erl

@@ -0,0 +1,73 @@
+%%==============================================================================
+%% Unused Includes diagnostics
+%%==============================================================================
+-module(els_unused_record_fields_diagnostics).
+
+%%==============================================================================
+%% Behaviours
+%%==============================================================================
+-behaviour(els_diagnostics).
+
+%%==============================================================================
+%% Exports
+%%==============================================================================
+-export([ is_default/0
+        , run/1
+        , source/0
+        ]).
+
+%%==============================================================================
+%% Includes
+%%==============================================================================
+-include("els_lsp.hrl").
+
+%%==============================================================================
+%% Callback Functions
+%%==============================================================================
+
+-spec is_default() -> boolean().
+is_default() ->
+  true.
+
+-spec run(uri()) -> [els_diagnostics:diagnostic()].
+run(Uri) ->
+  case filename:extension(Uri) of
+    <<".erl">> ->
+      case els_utils:lookup_document(Uri) of
+        {error, _Error} ->
+          [];
+        {ok, Document} ->
+          UnusedRecordFields = find_unused_record_fields(Document),
+          [make_diagnostic(POI) || POI <- UnusedRecordFields ]
+      end;
+    _ ->
+      []
+  end.
+
+-spec source() -> binary().
+source() ->
+  <<"UnusedRecordFields">>.
+
+%%==============================================================================
+%% Internal Functions
+%%==============================================================================
+-spec find_unused_record_fields(els_dt_document:item()) -> [poi()].
+find_unused_record_fields(Document) ->
+  Definitions = els_dt_document:pois(Document, [record_def_field]),
+  Usages = els_dt_document:pois(Document, [record_field]),
+  UsagesIds = [Id || #{id := Id} <- Usages],
+  [POI || #{id := Id} = POI <- Definitions, not lists:member(Id, UsagesIds)].
+
+-spec make_diagnostic(poi()) -> els_diagnostics:diagnostic().
+make_diagnostic(#{id := POIId, range := POIRange}) ->
+  Range = els_protocol:range(POIRange),
+  MacroName = case POIId of
+    {Id, Arity} ->
+      els_utils:to_binary(
+        lists:flatten(io_lib:format("~s/~b", [Id, Arity])));
+    Id -> atom_to_binary(Id, utf8)
+  end,
+  Message = <<"Unused record field: ", MacroName/binary>>,
+  Severity = ?DIAGNOSTIC_WARNING,
+  Source = source(),
+  els_diagnostics:make_diagnostic(Range, Message, Severity, Source).

apps/els_lsp/test/els_diagnostics_SUITE.erl

@@ -38,6 +38,7 @@
         , unused_includes_compiler_attribute/1
         , exclude_unused_includes/1
         , unused_macros/1
+        , unused_record_fields/1
         ]).
 
 %%==============================================================================
@@ -773,6 +774,25 @@ unused_macros(Config) ->
   ?assertEqual(Expected, lists:sort(F, Diagnostics)),
   ok.
 
+-spec unused_record_fields(config()) -> ok.
+unused_record_fields(Config) ->
+  Uri = ?config(diagnostics_unused_record_fields_uri, Config),
+  els_mock_diagnostics:subscribe(),
+  ok = els_client:did_save(Uri),
+  Diagnostics = els_mock_diagnostics:wait_until_complete(),
+  Expected = [ #{ message => <<"Unused record field: unused_field/field_d">>
+                , range =>
+                    #{ 'end' => #{character => 39, line => 5}
+                     , start => #{character => 32, line => 5}
+                     }
+                , severity => 2
+                , source => <<"UnusedRecordFields">>
+                }
+             ],
+  F = fun(#{message := M1}, #{message := M2}) -> M1 =< M2 end,
+  ?assertEqual(Expected, lists:sort(F, Diagnostics)),
+  ok.
+
 %%==============================================================================
 %% Internal Functions
 %%==============================================================================

apps/els_lsp/test/els_initialization_SUITE.erl

@@ -128,6 +128,7 @@ initialize_diagnostics_custom(Config) ->
              , <<"dialyzer">>
              , <<"unused_includes">>
              , <<"unused_macros">>
+             , <<"unused_record_fields">>
              ],
   Result = els_diagnostics:enabled_diagnostics(),
   ?assertEqual(Expected, Result),
@@ -148,6 +149,7 @@ initialize_diagnostics_invalid(Config) ->
              , <<"elvis">>
              , <<"unused_includes">>
              , <<"unused_macros">>
+             , <<"unused_record_fields">>
              ],
   ?assertEqual(Expected, Result),
   ok.

apps/els_lsp/test/els_test_utils.erl

@@ -156,6 +156,7 @@ sources() ->
   , diagnostics_unused_includes
   , diagnostics_unused_includes_compiler_attribute
   , diagnostics_unused_macros
+  , diagnostics_unused_record_fields
   , elvis_diagnostics
   , execute_command_suggest_spec
   , format_input