handle double quote escaping

Author: mythz

src/ServiceStack.Common/Script/JsToken.cs

@@ -146,6 +146,10 @@ public static bool FirstCharEquals(this string literal, char c) =>
         public static char SafeGetChar(this ReadOnlySpan<char> literal, int index) =>
             index >= 0 && index < literal.Length ? literal[index] : default(char);
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static bool SafeCharEquals(this ReadOnlySpan<char> literal, int index, char c) =>
+            index >= 0 && index < literal.Length && literal[index] == c;
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static char SafeGetChar(this ReadOnlyMemory<char> literal, int index) => literal.Span.SafeGetChar(index);
 
@@ -356,7 +360,8 @@ public static ReadOnlySpan<char> ParseJsToken(this ReadOnlySpan<char> literal, o
                     c = literal[i];
                     if (c == quoteChar)
                     {
-                        if (literal.SafeGetChar(i - 1) != '\\' || literal.SafeGetChar(i - 2) == '\\')
+                        if (!literal.SafeCharEquals(i - 1,'\\') ||
+                            (literal.SafeCharEquals(i - 2,'\\') && !literal.SafeCharEquals(i - 3,'\\')))
                             break;
                     }
 

tests/ServiceStack.WebHost.Endpoints.Tests/ScriptTests/JsonTests.cs

@@ -13,5 +13,13 @@ public void Does_escape_strings_in_JSON()
 
             Assert.That(obj["app.settings"], Is.EqualTo("debug true\nname MyApp\n"));
         }
+
+        [Test]
+        public void Can_parse_escaped_json()
+        {
+            var json = "{\"content\": \"warn(\\n          false,\\n          \\\"props in \\\\\\\"\\\" + (route.path) + \\\"\\\\\\\" is a \\\" + (typeof config) + \\\", \\\" +\\n          \\\"expecting an object, function or boolean.\\\"\\n        );\"}";
+            var obj = (Dictionary<string,object>)JSON.parse(json);
+            Assert.That(obj.ContainsKey("content"));
+        }
     }
 }