Implement Record.import macro that allows using private macros on public records

Author: yrashk

lib/elixir/lib/record.ex

@@ -44,6 +44,28 @@ defmodule Record do
     end
   end
 
+  @doc """
+  Import public record definition as a set of private macros (as defined by defrecordp/2)
+
+  ## Usage
+
+     Record.import Record.Module, as: macro_name
+
+  ## Example
+
+     defmodule Test do
+       Record.import File.Stat, as: :file_stat
+
+       def size(file_stat(size: size)), do: size
+     end
+
+  """
+  defmacro import(module, as: name) do
+    quote do
+      Record.defmacros(unquote(name), unquote(module).__record__(:fields), __ENV__, unquote(module))
+    end
+  end
+
   @doc """
   Main entry point for private records definition. It defines
   a set of macros with the given `name` and the fields specified
@@ -128,31 +150,32 @@ defmodule Record do
       end
 
   """
-  def defmacros(name, values, env) do
+  def defmacros(name, values, env, tag // nil) do
     escaped = lc value inlist values do
       { key, value } = convert_value(value)
       { key, Macro.escape(value) }
     end
 
     contents = quote do
+
       defmacrop unquote(name)() do
-        Record.access(__MODULE__, unquote(escaped), [], __CALLER__)
+        Record.access(unquote(tag) || __MODULE__, unquote(escaped), [], __CALLER__)
       end
 
       defmacrop unquote(name)(record) when is_tuple(record) do
-        Record.to_keywords(__MODULE__, unquote(escaped), record)
+        Record.to_keywords(unquote(tag) || __MODULE__, unquote(escaped), record)
       end
 
       defmacrop unquote(name)(args) do
-        Record.access(__MODULE__, unquote(escaped), args, __CALLER__)
+        Record.access(unquote(tag) || __MODULE__, unquote(escaped), args, __CALLER__)
       end
 
       defmacrop unquote(name)(record, key) when is_atom(key) do
-        Record.get(__MODULE__, unquote(escaped), record, key)
+        Record.get(unquote(tag) || __MODULE__, unquote(escaped), record, key)
       end
 
       defmacrop unquote(name)(record, args) do
-        Record.dispatch(__MODULE__, unquote(escaped), record, args, __CALLER__)
+        Record.dispatch(unquote(tag) || __MODULE__, unquote(escaped), record, args, __CALLER__)
       end
     end
 

lib/elixir/src/elixir_dispatch.erl

@@ -18,7 +18,7 @@ default_functions() ->
 default_macros() ->
   [ { ?BUILTIN, ordsets:union(in_elixir_macros(), in_erlang_macros()) } ].
 default_requires() ->
-  [ ?BUILTIN, 'Elixir.Kernel.Typespec' ].
+  [ ?BUILTIN, 'Elixir.Kernel.Typespec', 'Elixir.Record' ].
 
 find_import(Meta, Name, Arity, S) ->
   Tuple = { Name, Arity },

lib/elixir/test/elixir/kernel/errors_test.exs

@@ -119,7 +119,7 @@ defmodule Kernel.ErrorsTest do
   end
 
   test :unrequired_macro do
-    assert "nofile:2: tried to invoke macro Kernel.ErrorsTest.UnproperMacro.unproper/1 but module was not required. Required: Kernel, Kernel.Typespec" ==
+    assert "nofile:2: tried to invoke macro Kernel.ErrorsTest.UnproperMacro.unproper/1 but module was not required. Required: Kernel, Kernel.Typespec, Record" ==
       format_rescue 'defmodule Foo do\nKernel.ErrorsTest.UnproperMacro.unproper([])\nend'
   end
 

lib/elixir/test/elixir/record_test.exs

@@ -3,6 +3,16 @@ Code.require_file "../test_helper.exs", __FILE__
 defrecord RecordTest.FileInfo,
   Record.extract(:file_info, from_lib: "kernel/include/file.hrl")
 
+defmodule RecordTest.FileInfo.Helper do
+  Record.import RecordTest.FileInfo, as: :file_info
+
+  def new do
+    file_info
+  end
+
+  def size(file_info(size: size)), do: size
+end
+
 defrecord RecordTest.SomeRecord, a: 0, b: 1
 defrecord RecordTest.WithNoField, []
 
@@ -183,6 +193,11 @@ defmodule RecordTest do
     end)
   end
 
+  test :import do
+    assert RecordTest.FileInfo.Helper.new == RecordTest.FileInfo.new
+    assert RecordTest.FileInfo.Helper.size(RecordTest.FileInfo.new(size: 100)) == 100
+  end
+
   defp file_info do
     { :ok, file_info } = :file.read_file_info(__FILE__)
     file_info