FIXED: Also escape line terminators when writing graphql strings...

...as per https://spec.graphql.org/draft/#StringCharacter

Author: eshelyaron

graphql.pl

@@ -1182,6 +1182,10 @@
     graphql_write_value(V, Options).
 
 
+%! graphql_write_string(+Codes, +Options)// is det.
+%
+%  Generates Codes, except that codes in Codes that are not allowed in
+%  GraphQL string values are replaced by their escape sequences.
 graphql_write_string([], _Options) --> !, [].
 graphql_write_string([0'\"|T], Options) -->
     !,
@@ -1191,6 +1195,14 @@
     !,
     "\\\\",
     graphql_write_string(T, Options).
+graphql_write_string([0'\n|T], Options) -->
+    !,
+    "\\n",
+    graphql_write_string(T, Options).
+graphql_write_string([0'\r|T], Options) -->
+    !,
+    "\\r",
+    graphql_write_string(T, Options).
 graphql_write_string([H|T], Options) -->
     [H],
     graphql_write_string(T, Options).

test_graphql.pl

@@ -54,3 +54,24 @@
     graphql_read_document(codes(Codes), Doc, []).
 
 :- end_tests(graphql_round_trip).
+
+
+:- begin_tests(graphql_strings).
+
+test(escape_line_terminators) :-
+    String = "Hello,\r\nnewline!",
+    graphql_document_to_string(
+        {| graphql(String) ||
+           query { foo(bar: <String>
+                       baz: """
+                            Hello,
+                            multi-
+                            lines!
+                            """
+                      ) } |},
+        Text,
+        []
+    ),
+    string_lines(Text, [_]).
+
+:- end_tests(graphql_strings).