How to keep escape keys from a json? - json

Question

I´m making an application with dart / flutter and I need to keep the escape keys from the json server api response, how can I do that?
Example:
JSON reponse:
{"\"\"example\"\"": "value\'"}
Goal (after .fromJson and json.decode):
Class.example = "\"\"example\"\"";
Class.value = "value\'";

Answer 1

If you do jsonDecode(r'{"\"\"example\"\"": "value\'"}'), then you get a map with the key ""example"" and the value value' (the quotes are part of the string content here, not delimiters).
The backslashes are removed, which is to be expected because that's what the JSON specification says should happen. The escaped quotes are retained. The key does not become just example.
If you want to retain the backslashes too, then you don't actually want JSON decoding, because JSON decoding treats \" inside a string literal as introducing the character ".
If you wanted a string containing \"\"example\"\" from JSON decoding, then the original source needed to be "\\\"\\\"example\\\"\\\"".
So, if the sender of the JSON wanted you to see backslashes, they should have included and escaped those backslashes too.
If you JSON encode the string back, you get the backslashes again (at least for "), since jsonEncode('""example""') is "\"\"example\"\"".
If you really want access to the source code of the JSON input, I'd use a non-standard JSON parser, one which allows you to access the source instead of only the parsed value.
Example:
import "package:jsontool/jsontool.dart";
/// Parses [source] as JSON, but retains source escapes in strings.
Object? readJsonSourceStrings(String source) {
return _readJson(JsonReader.fromString(source));
}
Object? _readJson(JsonReader<StringSlice> reader) {
if (reader.tryObject()) {
var map = <String, Object?>{};
while (reader.hasNextKey()) {
var keySlice = reader.nextKeySource()!;
var key = keySlice.substring(1, keySlice.length - 1);
map[key] = _readJson(reader);
}
return map;
}
if (reader.tryArray()) {
var list = <Object?>[];
while (reader.hasNext()) {
list.add(_readJson(reader));
}
return list;
}
if (reader.checkString()) {
var slice = reader.expectAnyValueSource();
return slice.substring(1, slice.length - 1);
}
return reader.tryNum() ?? reader.tryBool() ??
(reader.tryNull() ? null : (throw "Unreachable"));
}
void main() {
var m = readJsonSourceStrings(r'''{"\"\"example\"\"":"value\'"}''');
print(m); // {\"\"example\"\": value\'}
}
(Disclaimer: I wrote the jsontool package.)