AK: JSON, Escape spacial character in string serialization

Author: https://github.com/asliturk
Commit: https://github.com/SerenityOS/serenity/commit/8e9776165f4
Pull-request: https://github.com/SerenityOS/serenity/pull/2455
Reviewed-by: https://github.com/JonArcherII
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/bugaevc

AK/JsonObject.h

@@ -31,6 +31,7 @@
 #include <AK/JsonObjectSerializer.h>
 #include <AK/JsonValue.h>
 #include <AK/String.h>
+#include <AK/StringImpl.h>
 
 namespace AK {
 
@@ -136,9 +137,36 @@ template<typename Builder>
 inline void JsonValue::serialize(Builder& builder) const
 {
     switch (m_type) {
-    case Type::String:
-        builder.appendf("\"%s\"", m_value.as_string->characters());
-        break;
+    case Type::String: {
+        auto size = m_value.as_string->length();
+        builder.append("\"");
+        for (size_t i = 0; i < size; i++) {
+            char ch = m_value.as_string->characters()[i];
+            switch (ch) {
+            case '\e':
+                builder.append("\\u001B");
+                break;
+            case '\b':
+                builder.append("\\b");
+                break;
+            case '\n':
+                builder.append("\\n");
+                break;
+            case '\t':
+                builder.append("\\t");
+                break;
+            case '\"':
+                builder.append("\\\"");
+                break;
+            case '\\':
+                builder.append("\\\\");
+                break;
+            default:
+                builder.appendf("%c", ch);
+            }
+        }
+        builder.append("\"");
+    } break;
     case Type::Array:
         m_value.as_array->serialize(builder);
         break;

AK/JsonParser.cpp

@@ -116,14 +116,22 @@ String JsonParser::consume_quoted_string()
         case 'f':
             buffer.append('\f');
             break;
-        case 'u':
-            consume();
-            consume();
-            consume();
-            consume();
-            // FIXME: This is obviously not correct, but we don't have non-ASCII support so meh.
-            buffer.append('?');
-            break;
+        case 'u': {
+            StringBuilder sb;
+            sb.append(consume());
+            sb.append(consume());
+            sb.append(consume());
+            sb.append(consume());
+
+            bool ok;
+            u32 codepoint = AK::StringUtils::convert_to_uint_from_hex(sb.to_string(), ok);
+            if (ok && codepoint < 128) {
+                buffer.append((char)codepoint);
+            } else {
+                // FIXME: This is obviously not correct, but we don't have non-ASCII support so meh.
+                buffer.append('?');
+            }
+        } break;
         default:
             buffer.append(escaped_ch);
             break;