Allow escaping linked translations

[Fasust]

I ran into an issue with linking translations and having them immediately followed by another word character.

Example:

{
  "common": {
    "nbsp": "\u00a0",
    "@nbsp": "No-Break Space https://unicode-explorer.com/c/00A0",
  },
   "message": "10@:common.nbspDays"
}

Message is linking to @:common.nbsp, but the link will be interpreted as @:common.nbspDays which is invalid.
My PR adds the option to escape linked translations:

{
  "common": {
    "nbsp": "\u00a0",
    "@nbsp": "No-Break Space https://unicode-explorer.com/c/00A0",
  },
   "message": "10@:{common.nbsp}Days"
}

[Tienisto]

Hi, thanks for the PR!
Do you know how other solutions handle this issue? This feature is inspired by linked translations of easy_localization but they probably followed the structure of Vue i18n.

I think it is better to handle it similar to how Dart handles interpolation ($ for greedy interpolation, ${} for edge cases).
Therefore, the following syntax might be safer to use (e.g. when somebody wants to have an actual @ in the string right after the linked translation):

{
  "message": "10@:{common.nbsp}Days"
}

Here, I surrounded the path with {...}
Let me know how you think about this. It might be a little bit more difficult to implement though.

[Fasust]

Thank you for the feedback @Tienisto
I updated the code to use your suggested escaping syntax

[Tienisto]

Please add the following tests in StringTextNode/StringInterpolation.braces (that will fail):

test('with links', () {
      final test = r'{myArg} @:myLink';
      final node = textNode(test, StringInterpolation.braces);
      expect(node.content, r'${myArg} ${_root.myLink}');
      expect(node.params, <String>{'myArg'});
    });

test('with escaped links', () {
      final test = r'{myArg} @:linkA @:{linkB}hello @:{linkC}';
      final node = textNode(test, StringInterpolation.braces);
      expect(node.content,
          r'${myArg} ${_root.linkA} ${_root.linkB}hello ${_root.linkC}');
      expect(node.params, <String>{'myArg'});
});

The main problem here is that we parse the linked translations after the interpolation ({myArg}). Therefore, @:{myLink} is parsed as an interpolation argument instead of a link

[Tienisto]

You probably need to parse the linked translations first and update replaceBracesInterpolation to add exclusion for matches starting with @:. Let me know if you need help

[Fasust]

Good catch @Tienisto , I added the tests you recommended. As far as I understand, ignoring matches leading with @: in replaceBracesInterpolation has solved the issue.

[Tienisto]

Nice!