Fix double escaped back slashes in string arguments

src/absinthe_parser.yrl

@@ -361,36 +361,7 @@ put_description(Node, Description) ->
 % String
 
 extract_quoted_string_token({_Token, _Loc, Value}) ->
-  unicode:characters_to_binary(process_string(lists:sublist(Value, 2, length(Value) - 2))).
-
-process_string(Escaped) ->
-  process_string(Escaped, []).
-
-process_string([], Acc) ->
-  lists:reverse(Acc);
-process_string([$\\, $" | T], Acc) ->
-  process_string(T, [$" | Acc]);
-process_string([$\\, $\\ | T], Acc) ->
-  process_string(T, [$\\ | Acc]);
-process_string([$\\, $/ | T], Acc) ->
-  process_string(T, [$/ | Acc]);
-process_string([$\\, $b | T], Acc) ->
-  process_string(T, [$\b | Acc]);
-process_string([$\\, $f | T], Acc) ->
-  process_string(T, [$\f | Acc]);
-process_string([$\\, $n | T], Acc) ->
-  process_string(T, [$\n | Acc]);
-process_string([$\\, $r | T], Acc) ->
-  process_string(T, [$\r | Acc]);
-process_string([$\\, $t | T], Acc) ->
-  process_string(T, [$\t | Acc]);
-process_string([$\\, $u, A, B, C, D | T], Acc) ->
-  process_string(T, [hexlist_to_utf8_binary([A, B, C, D]) | Acc]);
-process_string([H | T], Acc) ->
-  process_string(T, [H | Acc]).
-
-hexlist_to_utf8_binary(HexList) ->
-  unicode:characters_to_binary([httpd_util:hexlist_to_integer(HexList)]).
+  unicode:characters_to_binary(lists:sublist(Value, 2, length(Value) - 2)).
 
 % Block String
 

test/absinthe/integration/execution/escape_sequence_test.exs

@@ -0,0 +1,72 @@
+defmodule Absinthe.Phase.Document.Execution.EscapeSequenceTest do
+  use Absinthe.Case, async: true
+
+  defmodule Schema do
+    use Absinthe.Schema
+
+    query do
+      field :echo, :string do
+        arg :value, :string
+
+        resolve(fn %{value: input_string}, _ ->
+          {:ok, input_string}
+        end)
+      end
+    end
+  end
+
+  test "one slash" do
+    assert Absinthe.run(
+             ~S"""
+             {
+               echo(value: "\FOO")
+             }
+             """,
+             Schema
+           ) == {:ok, %{data: %{"echo" => ~S"\FOO"}}}
+  end
+
+  test "two slashes" do
+    assert Absinthe.run(
+             ~S"""
+             {
+               echo(value: "\\FOO")
+             }
+             """,
+             Schema
+           ) == {:ok, %{data: %{"echo" => ~S"\FOO"}}}
+  end
+
+  test "four slashes" do
+    assert Absinthe.run(
+             ~S"""
+             {
+               echo(value: "\\\\FOO")
+             }
+             """,
+             Schema
+           ) == {:ok, %{data: %{"echo" => ~S"\\FOO"}}}
+  end
+
+  test "eight slashes" do
+    assert Absinthe.run(
+             ~S"""
+             {
+               echo(value: "\\\\\\\\FOO")
+             }
+             """,
+             Schema
+           ) == {:ok, %{data: %{"echo" => ~S"\\\\FOO"}}}
+  end
+
+  test "literal slash n" do
+    assert Absinthe.run(
+             ~S"""
+             {
+               echo(value: "\\nFOO")
+             }
+             """,
+             Schema
+           ) == {:ok, %{data: %{"echo" => ~S"\nFOO"}}}
+  end
+end

test/absinthe/lexer_test.exs

@@ -27,6 +27,28 @@ defmodule Absinthe.LexerTest do
              Absinthe.Lexer.tokenize(@query)
   end
 
+  @query ~S"""
+  {
+    { foo(bar: "\\\\FOO") }
+  }
+  """
+  test "multiple escaped slashes" do
+    assert Absinthe.Lexer.tokenize(@query) ==
+             {:ok,
+              [
+                {:"{", {1, 1}},
+                {:"{", {2, 3}},
+                {:name, {2, 5}, 'foo'},
+                {:"(", {2, 8}},
+                {:name, {2, 9}, 'bar'},
+                {:":", {2, 12}},
+                {:string_value, {2, 14}, ~S("\\FOO") |> String.to_char_list()},
+                {:")", {2, 23}},
+                {:"}", {2, 25}},
+                {:"}", {3, 1}}
+              ]}
+  end
+
   @query """
   {
     foo(bar: \"""