Try to reproduce #671

test/credo/code/interpolation_helper_test.exs

@@ -454,4 +454,17 @@ defmodule Credo.Code.InterpolationHelperTest do
 
     assert expected == InterpolationHelper.replace_interpolations(source, "$")
   end
+
+  @tag needs_elixir: "1.7.0"
+  test "it should replace a single interpolation in a string" do
+    source = ~S"""
+    file_patt   = "*.{#{ Enum.join(file_exts, ",") }}"
+    """
+
+    expected = ~S"""
+    file_patt   = "*.{$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$}"
+    """
+
+    assert expected == InterpolationHelper.replace_interpolations(source, "$")
+  end
 end

test/credo/code_test.exs

@@ -251,6 +251,40 @@ defmodule Credo.CodeTest do
     assert match?({:ok, _}, Code.string_to_quoted(result))
   end
 
+  test "it should produce valid code /2" do
+    source = ~S"""
+    file_patt   = "*.{#{ Enum.join(file_exts, ",") }}"
+    """
+
+    expected = ~S"""
+    file_patt   = "                                  "
+    """
+
+    result = Credo.Code.clean_charlists_strings_sigils_and_comments(source)
+    result2 = Credo.Code.clean_charlists_strings_sigils_and_comments(result)
+
+    assert result == expected
+    assert result == result2, "clean_charlists_strings_sigils_and_comments/2 should be idempotent"
+    assert match?({:ok, _}, Code.string_to_quoted(result))
+  end
+
+  test "it should produce valid code /3" do
+    source = ~S"""
+    file_patt   = "*.{#{ Enum.join(file_exts, ",") }}"
+    """
+
+    expected = ~S"""
+    file_patt   = "                                  "
+    """
+
+    result = Credo.Code.clean_charlists_strings_and_sigils(source)
+    result2 = Credo.Code.clean_charlists_strings_and_sigils(result)
+
+    assert result == expected
+    assert result == result2, "clean_charlists_strings_and_sigils/2 should be idempotent"
+    assert match?({:ok, _}, Code.string_to_quoted(result))
+  end
+
   test "returns ast without metadata" do
     ast =
       {:__block__, [],