[erlang-ls#772] Only complete arguments for snippets.

This commit prevents the completion provider from providing arguments
for functions/macros when an editor does not enable snippets. With
snippet support, arguments are useful because they can be tabbed between,
but for an editor which does not implement snippets, the generated
arguments are mostly a hassle: you have to move back to replace the
arguments.

apps/els_lsp/src/els_completion_provider.erl

@@ -695,10 +695,16 @@ completion_item(#{kind := Kind, id := {F, A}, data := POIData}, Data, false)
        Kind =:= type_definition ->
   ArgsNames = maps:get(args, POIData),
   Label = io_lib:format("~p/~p", [F, A]),
+  SnippetSupport = snippet_support(),
+  Format =
+    case SnippetSupport of
+      true -> ?INSERT_TEXT_FORMAT_SNIPPET;
+      false -> ?INSERT_TEXT_FORMAT_PLAIN_TEXT
+    end,
   #{ label            => els_utils:to_binary(Label)
    , kind             => completion_item_kind(Kind)
-   , insertText       => snippet_function(F, ArgsNames)
-   , insertTextFormat => ?INSERT_TEXT_FORMAT_SNIPPET
+   , insertText       => format_function(F, ArgsNames, SnippetSupport)
+   , insertTextFormat => Format
    , data             => Data
    };
 completion_item(#{kind := Kind, id := {F, A}}, Data, true)
@@ -717,10 +723,16 @@ completion_item(#{kind := Kind = record, id := Name}, Data, _) ->
    };
 completion_item(#{kind := Kind = define, id := Name, data := Info}, Data, _) ->
   #{args := ArgNames} = Info,
+  SnippetSupport = snippet_support(),
+  Format =
+    case SnippetSupport of
+      true -> ?INSERT_TEXT_FORMAT_SNIPPET;
+      false -> ?INSERT_TEXT_FORMAT_PLAIN_TEXT
+    end,
   #{ label            => macro_label(Name)
    , kind             => completion_item_kind(Kind)
-   , insertText       => snippet_macro(Name, ArgNames)
-   , insertTextFormat => ?INSERT_TEXT_FORMAT_SNIPPET
+   , insertText       => format_macro(Name, ArgNames, SnippetSupport)
+   , insertTextFormat => Format
    , data             => Data
    }.
 
@@ -730,29 +742,30 @@ macro_label({Name, Arity}) ->
 macro_label(Name) ->
   atom_to_binary(Name, utf8).
 
--spec snippet_function(atom(), [{integer(), string()}]) -> binary().
-snippet_function(Name, Args) ->
-  snippet_args(atom_to_label(Name), Args).
+-spec format_function(atom(), [{integer(), string()}], boolean()) -> binary().
+format_function(Name, Args, SnippetSupport) ->
+  format_args(atom_to_label(Name), Args, SnippetSupport).
 
--spec snippet_macro( atom() | {atom(), non_neg_integer()}
-                   , [{integer(), string()}]) -> binary().
-snippet_macro({Name0, _Arity}, Args) ->
+-spec format_macro( atom() | {atom(), non_neg_integer()}
+                   , [{integer(), string()}]
+                   , boolean()) -> binary().
+format_macro({Name0, _Arity}, Args, SnippetSupport) ->
   Name = atom_to_binary(Name0, utf8),
-  snippet_args(Name, Args);
-snippet_macro(Name, none) ->
+  format_args(Name, Args, SnippetSupport);
+format_macro(Name, none, _SnippetSupport) ->
   atom_to_binary(Name, utf8).
 
--spec snippet_args(binary(), [{integer(), string()}]) -> binary().
-snippet_args(Name, Args0) ->
+-spec format_args(binary(), [{integer(), string()}], boolean()) -> binary().
+format_args(Name, Args0, SnippetSupport) ->
   Args =
-    case snippet_support() of
+    case SnippetSupport of
       false ->
-        [A || {_N, A} <- Args0];
+        [];
       true ->
-        [["${", integer_to_list(N), ":", A, "}"] || {N, A} <- Args0]
+        ArgList = [["${", integer_to_list(N), ":", A, "}"] || {N, A} <- Args0],
+        ["(", string:join(ArgList, ", "), ")"]
     end,
-  Snippet = [Name, "(", string:join(Args, ", "), ")"],
-  els_utils:to_binary(Snippet).
+  els_utils:to_binary([Name | Args]).
 
 -spec snippet_support() -> boolean().
 snippet_support() ->