Fix false positive for TrailingWhitespace

Refs #1203

Author: rrrene

lib/credo/code/strings.ex

@@ -589,7 +589,7 @@ defmodule Credo.Code.Strings do
          delimiter,
          empty_line_replacement
        ) do
-    parse_heredoc(t, acc, heredoc_acc, replacement, delimiter, empty_line_replacement)
+    parse_heredoc(t, acc, heredoc_acc <> "\\\"", replacement, delimiter, empty_line_replacement)
   end
 
   defp parse_heredoc(

test/credo/check/readability/trailing_white_space_test.exs

@@ -351,6 +351,36 @@ defmodule Credo.Check.Readability.TrailingWhiteSpaceTest do
     |> refute_issues()
   end
 
+  test "it should NOT report escaped heredocs in regular heredocs" do
+    ~S'''
+    defmodule Example do
+      @moduledoc ~S"""
+      config_yaml = \"\"\"
+      apiVersion: v1
+      \"\"\"
+      """
+    end
+    '''
+    |> to_source_file
+    |> run_check(@described_check)
+    |> refute_issues()
+  end
+
+  test "it should NOT report escaped heredocs in regular heredocs /2" do
+    ~S'''
+    defmodule Example do
+      @moduledoc ~S"""
+      \"\"\"
+      ...
+      \"\"\"
+      """
+    end
+    '''
+    |> to_source_file
+    |> run_check(@described_check)
+    |> refute_issues()
+  end
+
   #
   # cases raising issues
   #

test/credo/code/heredocs_test.exs

@@ -744,4 +744,30 @@ defmodule Credo.Code.HeredocsTest do
 
     assert result == result2, "Heredocs.replace_with_spaces/2 should be idempotent"
   end
+
+  test "should treat heredoc sigils correctly (issue #1202)" do
+    source =
+      ~S'''
+      defmodule Example do
+        @moduledoc ~S"""
+        \"\"\"
+        asdf
+        \"\"\"
+        """
+      end
+      '''
+
+    expected =
+      ~S'''
+      defmodule Example do
+        @moduledoc ~S"""
+        ......
+        ....
+        ......
+        """
+      end
+      '''
+
+    assert expected == source |> Heredocs.replace_with_spaces(".", ".", ".")
+  end
 end