Add documentation retrieval for module's built-in attributes

Closes #227

lib/elixir_sense/core/builtin_attributes.ex

@@ -6,7 +6,6 @@ defmodule ElixirSense.Core.BuiltinAttributes do
     impl
     derive
     enforce_keys
-    struct
     compile
     deprecated
     dialyzer
@@ -28,7 +27,39 @@ defmodule ElixirSense.Core.BuiltinAttributes do
     typedoc
     doc
     moduledoc
+    for
+    protocol
   )a
 
   def all, do: @list
+
+  def docs(attribute) when attribute in @list do
+    case Module.reserved_attributes() do
+      %{^attribute => %{doc: doc}} ->
+        doc
+
+      _ ->
+        # Older Elixir versions haven't document these attributes
+        # Reference: https://github.com/elixir-lang/elixir/commit/14c55d15afbf08b0d8289a4399a15b4109b6ac5a
+        case attribute do
+          :enforce_keys ->
+            "Ensures the given keys are always set when building the struct defined in the current module."
+
+          :fallback_to_any ->
+            "If set to `true` generates a default protocol implementation " <>
+              "for all types (inside `defprotocol`)."
+
+          :for ->
+            "The current module/type a protocol implementation is being defined for (inside `defimpl`)."
+
+          :protocol ->
+            "The current protocol being implemented (inside `defimpl`)."
+
+          _ ->
+            nil
+        end
+    end
+  end
+
+  def docs(_), do: nil
 end

lib/elixir_sense/providers/docs.ex

@@ -6,6 +6,7 @@ defmodule ElixirSense.Providers.Docs do
   alias ElixirSense.Core.Introspection
   alias ElixirSense.Core.State
   alias ElixirSense.Core.SurroundContext
+  alias ElixirSense.Core.BuiltinAttributes
 
   @spec all(any, State.Env.t(), State.mods_funs_to_positions_t(), State.types_t()) ::
           {actual_mod_fun :: String.t(), docs :: Introspection.docs()} | nil
@@ -31,17 +32,24 @@ defmodule ElixirSense.Providers.Docs do
 
     type = SurroundContext.to_binding(context, module)
 
-    mod_fun_docs(
-      type,
-      binding_env,
-      imports,
-      requires,
-      aliases,
-      module,
-      mods_funs,
-      metadata_types,
-      scope
-    )
+    case type do
+      {:attribute, attribute} ->
+        docs = BuiltinAttributes.docs(attribute)
+        if docs, do: {"@" <> Atom.to_string(attribute), %{docs: docs}}
+
+      _ ->
+        mod_fun_docs(
+          type,
+          binding_env,
+          imports,
+          requires,
+          aliases,
+          module,
+          mods_funs,
+          metadata_types,
+          scope
+        )
+    end
   end
 
   defp mod_fun_docs(
@@ -72,8 +80,6 @@ defmodule ElixirSense.Providers.Docs do
     end
   end
 
-  # TODO attr
-
   defp mod_fun_docs(
          {mod, fun},
          binding_env,

lib/elixir_sense/providers/suggestion/complete.ex

@@ -412,10 +412,16 @@ defmodule ElixirSense.Providers.Suggestion.Complete do
       attribute_name when is_atom(attribute_name) <- attribute_names,
       name = Atom.to_string(attribute_name),
       Matcher.match?(name, hint),
-      do: name
+      do: attribute_name
     )
     |> Enum.sort()
-    |> Enum.map(&%{kind: :attribute, name: &1})
+    |> Enum.map(
+      &%{
+        kind: :attribute,
+        name: Atom.to_string(&1),
+        summary: BuiltinAttributes.docs(&1)
+      }
+    )
     |> format_expansion()
   end
 
@@ -1042,8 +1048,8 @@ defmodule ElixirSense.Providers.Suggestion.Complete do
     [%{type: :variable, name: name}]
   end
 
-  defp to_entries(%{kind: :attribute, name: name}) do
-    [%{type: :attribute, name: "@" <> name}]
+  defp to_entries(%{kind: :attribute, name: name, summary: summary}) do
+    [%{type: :attribute, name: "@" <> name, summary: summary}]
   end
 
   defp to_entries(%{

lib/elixir_sense/providers/suggestion/reducers/common.ex

@@ -9,7 +9,8 @@ defmodule ElixirSense.Providers.Suggestion.Reducers.Common do
 
   @type attribute :: %{
           type: :attribute,
-          name: String.t()
+          name: String.t(),
+          summary: String.t()
         }
 
   @type variable :: %{

test/elixir_sense/docs_test.exs

@@ -1016,4 +1016,29 @@ defmodule ElixirSense.DocsTest do
            Flattens the given `list` of nested lists.
            """
   end
+
+  test "retrieve reserved module attributes documentation" do
+    buffer = """
+    defmodule MyModule do
+      @on_load :on_load
+
+      def on_load(), do: :ok
+    end
+    """
+
+    assert %{
+             actual_subject: "@on_load",
+             docs: %{docs: "A hook that will be invoked whenever the module is loaded."}
+           } = ElixirSense.docs(buffer, 2, 6)
+  end
+
+  test "retrieve unreserved module attributes documentation" do
+    buffer = """
+    defmodule MyModule do
+      @my_attribute nil
+    end
+    """
+
+    refute ElixirSense.docs(buffer, 2, 6)
+  end
 end

test/elixir_sense/providers/suggestion/complete_test.exs

@@ -1034,16 +1034,19 @@ defmodule ElixirSense.Providers.Suggestion.CompleteTest do
       scope: {:some, 0}
     }
 
-    assert expand('@numb', env) == [%{type: :attribute, name: "@number"}]
+    assert expand('@numb', env) == [%{type: :attribute, name: "@number", summary: nil}]
 
     assert expand('@num', env) ==
-             [%{type: :attribute, name: "@number"}, %{type: :attribute, name: "@numeral"}]
+             [
+               %{type: :attribute, name: "@number", summary: nil},
+               %{type: :attribute, name: "@numeral", summary: nil}
+             ]
 
     assert expand('@', env) ==
              [
-               %{name: "@nothing", type: :attribute},
-               %{type: :attribute, name: "@number"},
-               %{type: :attribute, name: "@numeral"}
+               %{name: "@nothing", type: :attribute, summary: nil},
+               %{type: :attribute, name: "@number", summary: nil},
+               %{type: :attribute, name: "@numeral", summary: nil}
              ]
   end
 
@@ -1067,7 +1070,13 @@ defmodule ElixirSense.Providers.Suggestion.CompleteTest do
     assert expand('@befo', env_outside_module) == []
 
     assert expand('@befo', env_module) ==
-             [%{type: :attribute, name: "@before_compile"}]
+             [
+               %{
+                 type: :attribute,
+                 name: "@before_compile",
+                 summary: "A hook that will be invoked before the module is compiled."
+               }
+             ]
   end
 
   test "kernel special form completion" do

test/elixir_sense/suggestions_test.exs

@@ -1513,53 +1513,92 @@ defmodule ElixirSense.SuggestionsTest do
            ] = ElixirSense.suggestions(buffer, 5, 9)
   end
 
-  test "lists attributes" do
-    buffer = """
-    defmodule MyModule do
-      @my_attribute1 true
-      @my_attribute2 false
-      @
-    end
-    """
+  describe "suggestions for module attributes" do
+    test "lists attributes" do
+      buffer = """
+      defmodule MyModule do
+        @my_attribute1 true
+        @my_attribute2 false
+        @
+      end
+      """
 
-    list =
-      ElixirSense.suggestions(buffer, 4, 4)
-      |> Enum.filter(fn s -> s.type == :attribute and s.name |> String.starts_with?("@my") end)
+      list =
+        ElixirSense.suggestions(buffer, 4, 4)
+        |> Enum.filter(fn s -> s.type == :attribute and s.name |> String.starts_with?("@my") end)
+        |> Enum.map(fn %{name: name} -> name end)
 
-    assert list == [
-             %{name: "@my_attribute1", type: :attribute},
-             %{name: "@my_attribute2", type: :attribute}
-           ]
-  end
+      assert list == ["@my_attribute1", "@my_attribute2"]
+    end
 
-  test "lists module attributes in module scope" do
-    buffer = """
-    defmodule MyModule do
-      @myattr "asd"
-      @moduledoc "asdf"
-      def some do
-        @m
+    test "lists module attributes in module scope" do
+      buffer = """
+      defmodule MyModule do
+        @myattr "asd"
+        @moduledoc "asdf"
+        def some do
+          @m
+        end
       end
+      """
+
+      list =
+        ElixirSense.suggestions(buffer, 2, 5)
+        |> Enum.filter(fn s -> s.type == :attribute end)
+        |> Enum.map(fn %{name: name} -> name end)
+
+      assert list == ["@macrocallback", "@moduledoc", "@myattr"]
+
+      list =
+        ElixirSense.suggestions(buffer, 5, 7)
+        |> Enum.filter(fn s -> s.type == :attribute end)
+        |> Enum.map(fn %{name: name} -> name end)
+
+      assert list == ["@myattr"]
     end
-    """
 
-    list =
-      ElixirSense.suggestions(buffer, 2, 5)
-      |> Enum.filter(fn s -> s.type == :attribute end)
+    test "built-in attributes should include documentation" do
+      buffer = """
+      defmodule MyModule do
+        @call
+        @enfor
+      end
+      """
 
-    assert list == [
-             %{name: "@macrocallback", type: :attribute},
-             %{name: "@moduledoc", type: :attribute},
-             %{name: "@myattr", type: :attribute}
-           ]
+      list =
+        ElixirSense.suggestions(buffer, 2, 7)
+        |> Enum.filter(fn s -> s.type == :attribute end)
 
-    list =
-      ElixirSense.suggestions(buffer, 5, 7)
-      |> Enum.filter(fn s -> s.type == :attribute end)
+      assert [%{summary: "Provides a specification for a behaviour callback."}] = list
 
-    assert list == [
-             %{name: "@myattr", type: :attribute}
-           ]
+      list =
+        ElixirSense.suggestions(buffer, 3, 8)
+        |> Enum.filter(fn s -> s.type == :attribute end)
+
+      assert [
+               %{
+                 summary:
+                   "Ensures the given keys are always set when building the struct defined in the current module."
+               }
+             ] = list
+    end
+
+    test "non built-in attributes should not include documentation" do
+      buffer = """
+      defmodule MyModule do
+        @myattr "asd"
+        def some do
+          @m
+        end
+      end
+      """
+
+      list =
+        ElixirSense.suggestions(buffer, 4, 6)
+        |> Enum.filter(fn s -> s.type == :attribute end)
+
+      assert [%{summary: nil}] = list
+    end
   end
 
   test "lists doc snippets in module body" do