Fixes to ExUnit.Diff, closes #9926

Author: josevalim

lib/elixir/lib/kernel/special_forms.ex

@@ -14,7 +14,8 @@ defmodule Kernel.SpecialForms do
   forms used to define tuple and binary data structures respectively.
 
   This module also documents macros that return information about Elixir's
-  compilation environment, such as (`__ENV__/0`, `__MODULE__/0`, `__DIR__/0` and `__CALLER__/0`).
+  compilation environment, such as (`__ENV__/0`, `__MODULE__/0`, `__DIR__/0`,
+  `__STACKTRACE__/0`, and `__CALLER__/0`).
 
   Additionally, it documents two special forms, `__block__/1` and
   `__aliases__/1`, which are not intended to be called directly by the

lib/ex_unit/lib/ex_unit/diff.ex

@@ -57,7 +57,8 @@ defmodule ExUnit.Diff do
   end
 
   defp diff_quoted({name, _, context} = left, right, env)
-       when is_atom(name) and is_atom(context) do
+       when is_atom(name) and is_atom(context) and
+              name not in [:__MODULE__, :__DIR__, :__STACKTRACE__, :__ENV__, :__CALLER__] do
     diff_var(left, right, env)
   end
 
@@ -94,7 +95,8 @@ defmodule ExUnit.Diff do
     end
   end
 
-  defp diff_quoted({:<>, _, _} = left, right, env) when is_binary(right) do
+  defp diff_quoted({:<>, _, [literal, _]} = left, right, env)
+       when is_binary(literal) and is_binary(right) do
     diff_string_concat(left, right, env)
   end
 
@@ -761,11 +763,10 @@ defmodule ExUnit.Diff do
     String.bag_distance(left, right) > 0.4
   end
 
-  defp parse_string({:<>, _, [literal, rest]}) do
+  defp parse_string({:<>, _, [literal, rest]}) when is_binary(literal) do
     {parsed, quoted, indexes, parsed_length} = parse_string(rest)
     literal_length = String.length(literal)
     length = literal_length + parsed_length
-
     {literal <> parsed, quoted, [literal_length | indexes], length}
   end
 

lib/ex_unit/test/ex_unit/diff_test.exs

@@ -141,6 +141,11 @@ defmodule ExUnit.DiffTest do
     refute_diff(^b = :a, "-^b-", "+:a+", pins)
   end
 
+  test "pseudo vars" do
+    assert_diff(__MODULE__ = ExUnit.DiffTest, [])
+    refute_diff(__MODULE__ = SomethingElse, "-__MODULE__-", "+SomethingElse+")
+  end
+
   test "integers" do
     assert_diff(123 = 123, [])
     assert_diff(-123 = -123, [])
@@ -749,7 +754,7 @@ defmodule ExUnit.DiffTest do
     )
   end
 
-  test "concat operator" do
+  test "concat binaries" do
     assert_diff("fox hops" <> " over the dog" = "fox hops over the dog", [])
     assert_diff("fox hops " <> "over " <> "the dog" = "fox hops over the dog", [])
 
@@ -783,6 +788,10 @@ defmodule ExUnit.DiffTest do
       ~s/"fox hops over the dog"/
     )
 
+    refute_diff("fox" <> " hops" = :a, ~s/-"fox" <> " hops"-/, "+:a+")
+  end
+
+  test "concat binaries with pin" do
     pins = %{{:x, nil} => " over the dog"}
 
     assert_diff("fox hops" <> x = "fox hops over the dog", x: " over the dog")
@@ -801,8 +810,16 @@ defmodule ExUnit.DiffTest do
       ~s/"fox hops over +t+he dog"/,
       pins
     )
+  end
 
-    refute_diff("fox" <> " hops" = :a, ~s/-"fox" <> " hops"-/, "+:a+")
+  test "concat binaries with specifiers" do
+    input = "foobar"
+
+    refute_diff(
+      <<trap::binary-size(3)>> <> "baz" = input,
+      "-<<trap::binary-size(3)>> <> \"baz\"-",
+      "+\"foobar\"+"
+    )
   end
 
   test "underscore" do