From 34ebffac16b1cf0f2d291b65b29a0cbf717cc57f Mon Sep 17 00:00:00 2001
From: Lukasz Samson <lukaszsamson@gmail.com>
Date: Wed, 4 Dec 2019 22:34:31 +0100
Subject: [PATCH 1/2] provide completions for protocol functions

---
 .../language_server/providers/completion.ex   | 28 +++++++++++++++++++
 .../test/providers/completion_test.exs        | 26 +++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/apps/language_server/lib/language_server/providers/completion.ex b/apps/language_server/lib/language_server/providers/completion.ex
index 06f82c4d9..8cd1c6d58 100644
--- a/apps/language_server/lib/language_server/providers/completion.ex
+++ b/apps/language_server/lib/language_server/providers/completion.ex
@@ -285,6 +285,34 @@ defmodule ElixirLS.LanguageServer.Providers.Completion do
     end
   end
 
+  defp from_completion_item(
+         %{
+           type: :protocol_function,
+           args: args,
+           spec: _spec,
+           name: name,
+           summary: summary,
+           arity: arity,
+           origin: origin
+         },
+         context
+       ) do
+    def_str = if(context[:def_before] == nil, do: "def ")
+
+    full_snippet = "#{def_str}#{snippet(name, args, arity)} do\n\t$0\nend"
+    label = "#{def_str}#{function_label(name, args, arity)}"
+
+    %__MODULE__{
+      label: label,
+      kind: :interface,
+      detail: "#{origin} protocol function",
+      documentation: summary,
+      insert_text: full_snippet,
+      priority: 2,
+      filter_text: name
+    }
+  end
+
   defp from_completion_item(%{type: :field, name: name, origin: origin}, _context) do
     %__MODULE__{
       label: to_string(name),
diff --git a/apps/language_server/test/providers/completion_test.exs b/apps/language_server/test/providers/completion_test.exs
index 99d20c7e5..6d4249062 100644
--- a/apps/language_server/test/providers/completion_test.exs
+++ b/apps/language_server/test/providers/completion_test.exs
@@ -55,4 +55,30 @@ defmodule ElixirLS.LanguageServer.Providers.CompletionTest do
       assert(Enum.any?(items, fn %{"label" => label} -> label == lfn end))
     end
   end
+
+  test "provides completions for protocol functions" do
+    text = """
+    defimpl Enumerable, for: MyModule do
+
+    #^
+    end
+    """
+
+    {line, char} = {1, 1}
+    TestUtils.assert_has_cursor_char(text, line, char)
+    {:ok, %{"items" => items}} = Completion.completion(text, line, char, true)
+
+    completions =
+      items
+      |> Enum.filter(&(&1["detail"] == "Enumerable protocol function"))
+      |> Enum.map(& &1["label"])
+      |> Enum.sort()
+
+    assert completions == [
+             "def count(enumerable)",
+             "def member?(enumerable,element)",
+             "def reduce(enumerable,acc,fun)",
+             "def slice(enumerable)"
+           ]
+  end
 end

From fc40bf60134e457b51a387086e395e01bcbb4dda Mon Sep 17 00:00:00 2001
From: Lukasz Samson <lukaszsamson@gmail.com>
Date: Thu, 5 Dec 2019 23:22:41 +0100
Subject: [PATCH 2/2] make test not depend on std lib

---
 apps/language_server/mix.exs                          |  4 ++++
 .../test/providers/completion_test.exs                | 10 +++-------
 .../test/support/fixtures/example_protocol.ex         | 11 +++++++++++
 3 files changed, 18 insertions(+), 7 deletions(-)
 create mode 100644 apps/language_server/test/support/fixtures/example_protocol.ex

diff --git a/apps/language_server/mix.exs b/apps/language_server/mix.exs
index 6aab9fdf9..d18f98b0f 100644
--- a/apps/language_server/mix.exs
+++ b/apps/language_server/mix.exs
@@ -10,6 +10,7 @@ defmodule ElixirLS.LanguageServer.Mixfile do
       config_path: "config/config.exs",
       deps_path: "../../deps",
       lockfile: "../../mix.lock",
+      elixirc_paths: elixirc_paths(Mix.env()),
       build_embedded: false,
       start_permanent: true,
       build_per_environment: false,
@@ -31,4 +32,7 @@ defmodule ElixirLS.LanguageServer.Mixfile do
       {:dialyxir, "~> 1.0.0-rc.6", runtime: false}
     ]
   end
+
+  defp elixirc_paths(:test), do: ["lib", "test/support"]
+  defp elixirc_paths(_), do: ["lib"]
 end
diff --git a/apps/language_server/test/providers/completion_test.exs b/apps/language_server/test/providers/completion_test.exs
index 6d4249062..adcac9f70 100644
--- a/apps/language_server/test/providers/completion_test.exs
+++ b/apps/language_server/test/providers/completion_test.exs
@@ -58,7 +58,7 @@ defmodule ElixirLS.LanguageServer.Providers.CompletionTest do
 
   test "provides completions for protocol functions" do
     text = """
-    defimpl Enumerable, for: MyModule do
+    defimpl ElixirLS.LanguageServer.Fixtures.ExampleProtocol, for: MyModule do
 
     #^
     end
@@ -70,15 +70,11 @@ defmodule ElixirLS.LanguageServer.Providers.CompletionTest do
 
     completions =
       items
-      |> Enum.filter(&(&1["detail"] == "Enumerable protocol function"))
+      |> Enum.filter(&(&1["detail"] =~ "protocol function"))
       |> Enum.map(& &1["label"])
-      |> Enum.sort()
 
     assert completions == [
-             "def count(enumerable)",
-             "def member?(enumerable,element)",
-             "def reduce(enumerable,acc,fun)",
-             "def slice(enumerable)"
+             "def my_fun(example,arg)"
            ]
   end
 end
diff --git a/apps/language_server/test/support/fixtures/example_protocol.ex b/apps/language_server/test/support/fixtures/example_protocol.ex
new file mode 100644
index 000000000..2e122eef6
--- /dev/null
+++ b/apps/language_server/test/support/fixtures/example_protocol.ex
@@ -0,0 +1,11 @@
+defprotocol ElixirLS.LanguageServer.Fixtures.ExampleProtocol do
+  @moduledoc """
+  ExampleProtocol protocol used in tests.
+  """
+
+  @doc """
+  Does what `my_fun` does for `t`
+  """
+  @spec my_fun(t, integer) :: binary
+  def my_fun(example, arg)
+end