Properly handle callback suggestion (#265)

* Property handle callback suggestion

* Fix snippet not adding arguments for callbacks

* Add tests for callback completion

* Update elixir_sense and make tests not depend on stdlib

Co-authored-by: Jason Axelson <jason.axelson@gmail.com>

Author: msaraiva

apps/language_server/lib/language_server/providers/completion.ex

@@ -281,14 +281,21 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
       insert_text = def_snippet(def_str, name, args, arity, options)
       label = "#{def_str}#{function_label(name, args, arity)}"
 
+      filter_text =
+        if def_str do
+          "#{def_str}#{name}"
+        else
+          name
+        end
+
       %__MODULE__{
         label: label,
         kind: :interface,
         detail: "#{origin} callback",
         documentation: summary,
         insert_text: insert_text,
         priority: 2,
-        filter_text: name,
+        filter_text: filter_text,
         tags: metadata_to_tags(metadata)
       }
     end
@@ -437,13 +444,13 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
 
   defp def_snippet(def_str, name, args, arity, opts) do
     if Keyword.get(opts, :snippets_supported, false) do
-      "#{def_str}#{function_snippet(name, args, arity)} do\n\t$0\nend"
+      "#{def_str}#{function_snippet(name, args, arity, opts)} do\n\t$0\nend"
     else
       "#{def_str}#{name}"
     end
   end
 
-  defp function_snippet(name, args, arity, opts \\ []) do
+  defp function_snippet(name, args, arity, opts) do
     cond do
       Keyword.get(opts, :capture_before?) && arity <= 1 ->
         Enum.join([name, "/", arity])

apps/language_server/test/providers/completion_test.exs

@@ -138,6 +138,51 @@ defmodule ElixirLS.LanguageServer.Providers.CompletionTest do
            ]
   end
 
+  test "provides completions for callbacks without `def` before" do
+    text = """
+    defmodule MyModule do
+      @behaviour ElixirLS.LanguageServer.Fixtures.ExampleBehaviour
+
+    # ^
+    end
+    """
+
+    {line, char} = {2, 2}
+    TestUtils.assert_has_cursor_char(text, line, char)
+    {:ok, %{"items" => items}} = Completion.completion(text, line, char, @supports)
+
+    first_completion =
+      items
+      |> Enum.filter(&(&1["detail"] =~ "callback"))
+      |> Enum.at(0)
+
+    assert first_completion["label"] =~ "def build_greeting"
+
+    assert first_completion["insertText"] == "def build_greeting(${1:name}) do\n\t$0\nend"
+  end
+
+  test "provides completions for callbacks with `def` before" do
+    text = """
+    defmodule MyModule do
+      @behaviour ElixirLS.LanguageServer.Fixtures.ExampleBehaviour
+
+      def
+       # ^
+    end
+    """
+
+    {line, char} = {3, 5}
+    TestUtils.assert_has_cursor_char(text, line, char)
+    {:ok, %{"items" => items}} = Completion.completion(text, line, char, @supports)
+
+    first_completion =
+      items
+      |> Enum.filter(&(&1["detail"] =~ "callback"))
+      |> Enum.at(0)
+
+    assert first_completion["label"] =~ "def build_greeting"
+  end
+
   test "returns module completions after pipe" do
     text = """
     defmodule MyModule do

apps/language_server/test/support/fixtures/example_behaviour.ex

@@ -0,0 +1,4 @@
+defmodule ElixirLS.LanguageServer.Fixtures.ExampleBehaviour do
+  @callback greet_world() :: nil
+  @callback build_greeting(name :: String.t()) :: String.t()
+end

mix.lock

@@ -1,7 +1,7 @@
 %{
   "dialyxir": {:hex, :dialyxir, "1.0.0", "6a1fa629f7881a9f5aaf3a78f094b2a51a0357c843871b8bc98824e7342d00a5", [:mix], [{:erlex, ">= 0.2.6", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "aeb06588145fac14ca08d8061a142d52753dbc2cf7f0d00fc1013f53f8654654"},
   "docsh": {:hex, :docsh, "0.7.2", "f893d5317a0e14269dd7fe79cf95fb6b9ba23513da0480ec6e77c73221cae4f2", [:rebar3], [{:providers, "1.8.1", [hex: :providers, repo: "hexpm", optional: false]}], "hexpm", "4e7db461bb07540d2bc3d366b8513f0197712d0495bb85744f367d3815076134"},
-  "elixir_sense": {:git, "https://github.com/elixir-lsp/elixir_sense.git", "6395dd568e542a8b05a2d3dee61f02142564f30d", []},
+  "elixir_sense": {:git, "https://github.com/elixir-lsp/elixir_sense.git", "648a501c42c16a610cb67c29f0beb0c087171849", []},
   "erl2ex": {:git, "https://github.com/dazuma/erl2ex.git", "244c2d9ed5805ef4855a491d8616b8842fef7ca4", []},
   "erlex": {:hex, :erlex, "0.2.6", "c7987d15e899c7a2f34f5420d2a2ea0d659682c06ac607572df55a43753aa12e", [:mix], [], "hexpm", "2ed2e25711feb44d52b17d2780eabf998452f6efda104877a3881c2f8c0c0c75"},
   "forms": {:hex, :forms, "0.0.1", "45f3b10b6f859f95f2c2c1a1de244d63855296d55ed8e93eb0dd116b3e86c4a6", [:rebar3], [], "hexpm", "530f63ed8ed5a171f744fc75bd69cb2e36496899d19dbef48101b4636b795868"},