Add Flutter 3 Compatibility

[JaffaKetchup]

• Fixed example compatibility with Flutter 3: fixes [BUG] Example cannot compile with Flutter 3 on Android #1234
• Changed linter rules & fixed other linter errors/warnings
  • Existing rule exceptions were redundant as they were not defined properly and so the analyzer did not parse them
  • Therefore, many of the exceptions' cases were already fixed in a previous PR
  • Added exception for 'library_private_types_in_public_api'

[ibrierley]

I think my only problem with this is flutter_lints. Forcing it to ^2.0.1 in the pubspec.yaml (in example and root folder), forces users to upgrade to Flutter3 (or a later flutter version anyway), which feels a bit too soon. Is there any specific reason to require this, and not just have ">=1.0.4" or something ?

[JaffaKetchup]

I would agree if it does force Flutter 3 usage then it needs to be changed. But as far as I can see, in both flutter_lints and lints (it's dependency), Flutter 3 usage isn't forced. Maybe I'm misunderstanding something?

https://github.com/flutter/packages/blob/main/packages/flutter_lints/pubspec.yaml
https://github.com/dart-lang/lints/blob/main/pubspec.yaml

[ibrierley]

Sorry, yes, it doesn't force 3, but >= 2.17.0 which is ahead of what I typically use 2.15.1 (so guessing others would be similar). I'm not sure whats a minimum most are on.

[ibrierley]

Sorry again, that's the Dart version, looks like typically I'm on Dart 2.15.1, flutter 2.8.1,

[JaffaKetchup]

Ok, I've relaxed the constraints. Note that the checks use the latest version available every time, so the code formatting must still match those rules, even if an editor may not necessarily warn the developer about those infractions.

[ibrierley]

I think flutter_map_example pubspec.yaml needs to be changed as well to match

[JaffaKetchup]

I did change the example as well.

[ibrierley]

Strange, I can see the files updated in here, but it doesn't seem to be checking the correct version out, maybe something gone astray my end. Will dig.

[ibrierley]

Ok, all good for me now, thanks!