Add support for inlay hints (#1504)

Argument names in function calls will now show up as inlay hints.

Inlay hints are disabled by default, enable by adding this to config:

    inlay_hints_enabled: true

Additional changes:
* Add functional API to submit job results to els_server
* Improve completions by extracting argument names from spec.
* Improve completions by extracting argument names from all function clauses.
* Gracefully handle parsing of missing header file

apps/els_core/include/els_core.hrl

@@ -602,6 +602,35 @@
     command => els_command:command()
 }.
 
+%%------------------------------------------------------------------------------
+%% Inlay hint
+%%------------------------------------------------------------------------------
+-define(INLAY_HINT_KIND_TYPE, 1).
+-define(INLAY_HINT_KIND_PARAMETER, 2).
+
+-type inlay_hint_kind() ::
+    ?INLAY_HINT_KIND_TYPE
+    | ?INLAY_HINT_KIND_PARAMETER.
+
+-type inlay_hint_label_part() ::
+    #{
+        value := binary(),
+        tooltip => binary() | markup_content(),
+        location => location(),
+        command => els_command:command()
+    }.
+
+-type inlay_hint() :: #{
+    position := position(),
+    label := binary() | [inlay_hint_label_part()],
+    kind => inlay_hint_kind(),
+    textEdits => [text_edit()],
+    tooltip => binary() | markup_content(),
+    paddingLeft => boolean(),
+    paddingRight => boolean(),
+    data => map()
+}.
+
 %%------------------------------------------------------------------------------
 %% Workspace
 %%------------------------------------------------------------------------------

apps/els_core/src/els_client.erl

@@ -57,7 +57,8 @@
     preparecallhierarchy/3,
     callhierarchy_incomingcalls/1,
     callhierarchy_outgoingcalls/1,
-    get_notifications/0
+    get_notifications/0,
+    inlay_hint/2
 ]).
 
 -export([handle_responses/1]).
@@ -276,6 +277,10 @@ get_notifications() ->
 handle_responses(Responses) ->
     gen_server:cast(?SERVER, {handle_responses, Responses}).
 
+-spec inlay_hint(uri(), range()) -> ok.
+inlay_hint(Uri, Range) ->
+    gen_server:call(?SERVER, {inlay_hint, {Uri, Range}}).
+
 %%==============================================================================
 %% gen_server Callback Functions
 %%==============================================================================
@@ -462,6 +467,7 @@ method_lookup(implementation) -> <<"textDocument/implementation">>;
 method_lookup(folding_range) -> <<"textDocument/foldingRange">>;
 method_lookup(semantic_tokens) -> <<"textDocument/semanticTokens/full">>;
 method_lookup(preparecallhierarchy) -> <<"textDocument/prepareCallHierarchy">>;
+method_lookup(inlay_hint) -> <<"textDocument/inlayHint">>;
 method_lookup(callhierarchy_incomingcalls) -> <<"callHierarchy/incomingCalls">>;
 method_lookup(callhierarchy_outgoingcalls) -> <<"callHierarchy/outgoingCalls">>;
 method_lookup(workspace_symbol) -> <<"workspace/symbol">>;
@@ -476,6 +482,11 @@ request_params({document_symbol, {Uri}}) ->
     #{textDocument => TextDocument};
 request_params({workspace_symbol, {Query}}) ->
     #{query => Query};
+request_params({inlay_hint, {Uri, Range}}) ->
+    #{
+        textDocument => #{uri => Uri},
+        range => Range
+    };
 request_params({workspace_executecommand, {Command, Args}}) ->
     #{
         command => Command,

apps/els_core/src/els_config.erl

@@ -172,6 +172,7 @@ do_initialize(RootUri, Capabilities, InitOptions, {ConfigPath, Config}) ->
     RefactorErl = maps:get("refactorerl", Config, notconfigured),
     Providers = maps:get("providers", Config, #{}),
     EdocParseEnabled = maps:get("edoc_parse_enabled", Config, true),
+    InlayHintsEnabled = maps:get("inlay_hints_enabled", Config, false),
     Formatting = maps:get("formatting", Config, #{}),
     DocsMemo = maps:get("docs_memo", Config, false),
 
@@ -248,6 +249,7 @@ do_initialize(RootUri, Capabilities, InitOptions, {ConfigPath, Config}) ->
     ok = set(edoc_custom_tags, EDocCustomTags),
     ok = set(edoc_parse_enabled, EdocParseEnabled),
     ok = set(incremental_sync, IncrementalSync),
+    ok = set(inlay_hints_enabled, InlayHintsEnabled),
     ok = set(
         indexing,
         maps:merge(

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

@@ -0,0 +1,26 @@
+-module(inlay_hint).
+-export([test/0]).
+
+-record(foo, {}).
+
+test() ->
+    a(1, 2),
+    b(1, 2),
+    c(1),
+    d(1, 2),
+    lists:append([], []).
+
+a(Hej, Hoj) ->
+    Hej + Hoj.
+
+b(x, y) ->
+    0;
+b(A, _B) ->
+    A.
+
+c(#foo{}) ->
+    ok.
+
+d([1,2,3] = Foo,
+  Bar = #{hej := 123}) ->
+    ok.

apps/els_lsp/src/els_arg.erl

@@ -0,0 +1,25 @@
+-module(els_arg).
+-export([name/1]).
+-export([name/2]).
+-export([index/1]).
+-export_type([arg/0]).
+
+-type arg() :: #{
+    index := pos_integer(),
+    name := string() | undefined,
+    range => els_poi:poi_range()
+}.
+
+-spec name(arg()) -> string().
+name(Arg) ->
+    name("Arg", Arg).
+
+-spec name(string(), arg()) -> string().
+name(Prefix, #{index := N, name := undefined}) ->
+    Prefix ++ integer_to_list(N);
+name(_Prefix, #{name := Name}) ->
+    Name.
+
+-spec index(arg()) -> string().
+index(#{index := Index}) ->
+    integer_to_list(Index).

apps/els_lsp/src/els_background_job.erl

@@ -9,6 +9,7 @@
 -export([
     new/1,
     list/0,
+    list_titles/0,
     stop/1,
     stop_all/0
 ]).
@@ -82,6 +83,22 @@ list() ->
             supervisor:which_children(els_background_job_sup)
     ].
 
+%% @doc Return the list of running background jobs
+-spec list_titles() -> [any()].
+list_titles() ->
+    Children = supervisor:which_children(els_background_job_sup),
+    lists:flatmap(
+        fun({_Id, Pid, _Type, _Modules}) ->
+            case catch gen_server:call(Pid, get_title) of
+                {ok, Title} ->
+                    [Title];
+                _ ->
+                    []
+            end
+        end,
+        Children
+    ).
+
 %% @doc Terminate a background job
 -spec stop(pid()) -> ok.
 stop(Pid) ->
@@ -145,6 +162,12 @@ init(#{entries := Entries, title := Title} = Config) ->
 
 -spec handle_call(any(), {pid(), any()}, state()) ->
     {noreply, state()}.
+handle_call(
+    get_title,
+    _From,
+    #{config := #{title := Title}} = State
+) ->
+    {reply, {ok, Title}, State};
 handle_call(_Request, _From, State) ->
     {noreply, State}.
 

apps/els_lsp/src/els_code_actions.erl

@@ -264,7 +264,7 @@ format_args(Document, Arity, Range) ->
     ],
     case Matches of
         [#{data := #{args := Args0}} | _] ->
-            string:join([A || {_N, A} <- Args0], ", ");
+            string:join([els_arg:name(A) || A <- Args0], ", ");
         [] ->
             string:join(lists:duplicate(Arity, "_"), ", ")
     end.

apps/els_lsp/src/els_code_lens_provider.erl

@@ -42,11 +42,7 @@ run_lenses_job(Uri) ->
             end,
         entries => [Document],
         title => <<"Lenses">>,
-        on_complete =>
-            fun(Lenses) ->
-                els_server ! {result, Lenses, self()},
-                ok
-            end
+        on_complete => fun els_server:register_result/1
     },
     {ok, Pid} = els_background_job:new(Config),
     Pid.

apps/els_lsp/src/els_compiler_diagnostics.erl

@@ -117,20 +117,30 @@ parse(Uri) ->
             _ ->
                 undefined
         end,
-    {ok, Epp} = epp:open([
+    Options = [
         {name, FileName},
         {includes, els_config:get(include_paths)},
         {macros, [
             {'MODULE', dummy_module, redefine},
             {'MODULE_STRING', "dummy_module", redefine}
         ]}
-    ]),
-    Res = [
-        epp_diagnostic(Document, Anno, Module, Desc)
-     || {error, {Anno, Module, Desc}} <- epp:parse_file(Epp)
     ],
-    epp:close(Epp),
-    Res.
+    case epp:open(Options) of
+        {ok, Epp} ->
+            Res = [
+                epp_diagnostic(Document, Anno, Module, Desc)
+             || {error, {Anno, Module, Desc}} <- epp:parse_file(Epp)
+            ],
+            epp:close(Epp),
+            Res;
+        {error, Reason} ->
+            ?LOG_ERROR(
+                "Failed to open: ~s\n"
+                "Reason: ~p",
+                [FileName, Reason]
+            ),
+            []
+    end.
 
 %% Possible cases to handle
 %% ,{error,{19,erl_parse,["syntax error before: ","'-'"]}}