Store record metadata in the documentation chunk (#13939)

Author: josevalim

lib/elixir/lib/record.ex

@@ -36,10 +36,9 @@ defmodule Record do
 
   ## Reflection
 
-  A list of all records in a module, if any, can be retrieved by reading the
-  `@__records__` module attribute. It returns a list of maps with the record
-  kind, name, tag, and fields. The attribute is only available inside the
-  module definition.
+  The record tag and its fields are stored as metadata in the "Docs" chunk
+  of the record definition macro. You can retrieve the documentation for
+  a module by calling `Code.fetch_docs/1`.
   """
 
   @doc """
@@ -253,6 +252,7 @@ defmodule Record do
       tag = tag || name
       fields = Record.__record__(__MODULE__, :defrecord, name, tag, kv)
 
+      @doc record: {tag, fields}
       defmacro unquote(name)(args \\ []) do
         Record.__access__(unquote(tag), unquote(fields), args, __CALLER__)
       end
@@ -312,6 +312,8 @@ defmodule Record do
     error_on_duplicate_record(module, name)
 
     fields = fields(kind, kv)
+
+    # TODO: Remove me on Elixir v2.0
     Module.register_attribute(module, :__records__, accumulate: true)
 
     Module.put_attribute(module, :__records__, %{

lib/elixir/test/elixir/record_test.exs

@@ -341,6 +341,20 @@ defmodule RecordTest do
     end
   end
 
+  test "docs metadata" do
+    import PathHelpers
+
+    write_beam(
+      defmodule Metadata do
+        Record.defrecord(:user, foo: 0, bar: "baz")
+      end
+    )
+
+    {:docs_v1, 348, :elixir, "text/markdown", _, %{}, docs} = Code.fetch_docs(RecordTest.Metadata)
+    {{:macro, :user, 1}, _meta, _sig, _docs, metadata} = List.keyfind(docs, {:macro, :user, 1}, 0)
+    assert %{record: {:user, [foo: 0, bar: "baz"]}} = metadata
+  end
+
   describe "warnings" do
     import ExUnit.CaptureIO