Add a trailing comma

[vogella]

Thanks for your tools. Would be nice to always add a trailing comma, which is the standard in Dart.

Example:

{
    "tags": [
        "flutter"
    ],
    "owner": {
        "reputation": 354,
        "user_id": 6324029,
        "user_type": "registered",
        "profile_image": "https://www.gravatar.com/avatar/293ab6d0d3810adb641b0d37b800f774?s=128&d=identicon&r=PG&f=1",
        "display_name": "hoangquyy",
        "link": "https://stackoverflow.com/users/6324029/hoangquyy"
    },
    "is_answered": false,
    "view_count": 6,
    "answer_count": 1,
    "score": 0,
    "last_activity_date": 1574754851,
    "creation_date": 1574754058,
    "question_id": 59045950,
    "link": "https://stackoverflow.com/questions/59045950/can-we-download-video-and-play-it-with-flutter-without-add-it-into-asset",
    "title": "Can we download video and play it with flutter without add it into asset?"
}

Should write (basically adding a , after this.link

  Owner({
    this.reputation,
    this.userId,
    this.userType,
    this.profileImage,
    this.displayName,
    this.link,
  });

instead of:

Owner(
      {this.reputation,
      this.userId,
      this.userType,
      this.profileImage,
      this.displayName,
      this.link});

[javiercbk]

Thanks for your suggestion. The library relies on dart_style for all the formatting. I'm surprised that dart_style does not add the trailing comma.

The using dart_style is something mentioned in "Effective Dart". But the same page makes this explicit point:

Note that dartfmt does 99% of this for you, but the last 1% is you. It does not split long string literals to fit in 80 columns, so you have to do that manually.

So I think it is fair to say that this library should fix this, but I won't be able to easily fix this if the dart_style library erases the trailing comma.

I'll research this.