Make sure unintialized @Attribute warnings points to the correct file

Author: Yuki Ito

lib/elixir/lib/exception.ex

@@ -282,12 +282,13 @@ defmodule Exception do
     trace = trace || try do
       throw(:stacktrace)
     catch
-      :stacktrace -> Enum.drop(:erlang.get_stacktrace, 1)
+      :stacktrace -> Enum.drop(:erlang.get_stacktrace, 2)
     end
 
-    if entry = Enum.at(trace, 1) do
-      format_stacktrace_entry(entry)
-    else
+    case trace do
+      [entry|_] ->
+        format_stacktrace_entry(entry)
+      _ ->
       "nofile:0: "
     end
   end

lib/elixir/lib/kernel.ex

@@ -2063,17 +2063,18 @@ defmodule Kernel do
 
   # @attribute or @attribute()
   defp do_at(args, name, function?, env) when is_atom(args) or args == [] do
+    stack =
+      case bootstraped?(Path) do
+        true  -> env.stacktrace
+        false -> []
+      end
+
     case function? do
       true ->
-        stack =
-          case bootstraped?(Path) do
-            true  -> env.stacktrace
-            false -> []
-          end
         attr = Module.get_attribute(env_module(env), name, stack)
         :erlang.element(1, :elixir_quote.escape(attr, false))
       false ->
-        quote do: Module.get_attribute(__MODULE__, unquote(name), true)
+        quote do: Module.get_attribute(__MODULE__, unquote(name), unquote(Macro.escape(stack)))
     end
   end
 

lib/elixir/test/elixir/fixtures/attribute_warning.ex

@@ -0,0 +1,3 @@
+defmodule AttributeWarning do
+  @foo
+end

lib/elixir/test/elixir/kernel/warning_test.exs

@@ -4,6 +4,8 @@ defmodule Kernel.WarningTest do
   use ExUnit.Case
   import ExUnit.CaptureIO
 
+  import PathHelpers
+
   defp capture_err(fun) do
     capture_io(:stderr, fun)
   end
@@ -329,6 +331,14 @@ defmodule Kernel.WarningTest do
     purge Sample
   end
 
+  test :undefined_module_attribute_with_file do
+    assert capture_err(fn ->
+      Code.load_file(fixture_path("attribute_warning.ex"))
+    end) =~ "attribute_warning.ex:2: AttributeWarning (module) undefined module attribute @foo, please remove access to @foo or explicitly set it to nil before access"
+  after
+    purge AttributeWarning
+  end
+
   test :in_guard_empty_list do
     assert capture_err(fn ->
       Code.eval_string """