dart:ui types not handled by mobx_codegen properly on Flutter stable/beta

[Bwolfs2]

Some people in the community are reporting to me that the Color class when placed in Observable is generating Dynamic.

  @observable
  Color colorPrimary = null;

And generated it:

  @override
  dynamic get colorPrimary {
    _$colorPrimaryAtom.context.enforceReadPolicy(_$colorPrimaryAtom);
    _$colorPrimaryAtom.reportObserved();
    return super.colorPrimary;
  }

The Color class is blocked somehow and we are unable to solve it, has anyone had this problem?

[irvine5k]

I have this problem too, should I worry about it with another classes?

[shyndman]

This should work, and I have verified that it is working correctly locally. So don't worry. We'll get you fixed up. :)

Can you please verify that you're running the latest version of mobx_codegen (0.4.0+1)? What version does your pubspec.lock say it's using?

[irvine5k]

mobx_codegen: ^0.4.0+1
build_runner: ^1.7.3


 mobx_codegen:
    dependency: "direct dev"
    description:
      name: mobx_codegen
      url: "https://pub.dartlang.org"
    source: hosted
    version: "0.4.0+1"

When generate files throws this error on Class:

'_$Cartouche.backColor' ('List<dynamic> Function()') isn't a valid override of '_Cartouche.backColor' ('List<Color> Function()').dart(invalid_override)

This is the store class:

import 'package:flutter/material.dart';
import 'package:mobx/mobx.dart';

part 'cartouche.g.dart';

class Cartouche = _Cartouche with _$Cartouche;

abstract class _Cartouche with Store {

  @observable
  List<bool> color = List.generate(60, (i) => false);

  @observable
  List<Color> backColor = List.generate(60, (i) => Colors.transparent);

}

Generated code:

@override
  List<dynamic> get backColor {
    _$backColorAtom.context.enforceReadPolicy(_$backColorAtom);
    _$backColorAtom.reportObserved();
    return super.backColor;
  }

  @override
  set backColor(List<dynamic> value) {
    _$backColorAtom.context.conditionallyRunInAction(() {
      super.backColor = value;
      _$backColorAtom.reportChanged();
    }, _$backColorAtom, name: '${_$backColorAtom.name}_set');
  }

[pavanpodila]

This looks like a bug in the analyzer package. The visitor for field-element itself is returning List<dynamic> instead of List<Color>. @shyndman looks like we may need to see if a more recent version of analyzer fixes this.

  void visitFieldElement(FieldElement element) { } // element is List<dynamic> !!!

Note that this is not a bug with mobx_codgen, but with the analyzer package. We will investigate and get back. Thanks so much for bringing to our attention!

[shyndman]

Do you have a local repro @pavanpodila?

@irvine5k, can you attach your entire pubspec.lock?

[pavanpodila]

@shyndman pls see this commit that shows the test that fails: 2b46073

If you place you debug breakpoint for visitFieldElement, you can see the failing type as List<dynamic>

[irvine5k]

Do you have a local repro @pavanpodila?

@irvine5k, can you attach your entire pubspec.lock?

mobx_color_pubspec.lock.txt

[shyndman]

@shyndman pls see this commit that shows the test that fails: 2b46073

If you place you debug breakpoint for visitFieldElement, you can see the failing type as List<dynamic>

@pavanpodila Are you running this test using Flutter's Dart, or a Dart installed standalone?

Including the Flutter dependency isn't enough. build_resolvers, which is responsible for configuring the analyzer, checks to see whether the Dart belongs to Flutter, and if so, includes the dart:ui and Flutter types: https://github.com/dart-lang/build/blob/master/build_resolvers/lib/src/resolver.dart#L326

I was able to uncomment the lines in that commit to see the code generator working appropriately.

[shyndman]

Thanks for the lock @irvine5k. Can I get you to try something?

From your project directory, can you run:
flutter clean && flutter packages pub run build_runner build --delete-conflicting-outputs

After that, do you still get the dynamics?

[irvine5k]

Thanks for the lock @irvine5k. Can I get you to try something?

From your project directory, can you run:
flutter clean && flutter packages pub run build_runner build --delete-conflicting-outputs

After that, do you still get the dynamics?

Yes, I do.

@override
  List<dynamic> get backColor {
    _$backColorAtom.context.enforceReadPolicy(_$backColorAtom);
    _$backColorAtom.reportObserved();
    return super.backColor;
  }

[shyndman]

Hm. Bear with me.

@irvine5k, I created a very simple project, containing only cartouche.dart and the necessary dependencies. My local version is generating code correctly.

Can you clone https://github.com/shyndman/mobx_list_color_repro, and run flutter packages pub run build_runner build? Does cartouche.g.dart get generated properly there?

[irvine5k]

Hm. Bear with me.

@irvine5k, I created a very simple project, containing only cartouche.dart and the necessary dependencies. My local version is generating code correctly.

Can you clone https://github.com/shyndman/mobx_list_color_repro, and run flutter packages pub run build_runner build? Does cartouche.g.dart get generated properly there?

@shyndman It does not work for me.

@override
  List get backColor {
    _$backColorAtom.context.enforceReadPolicy(_$backColorAtom);
    _$backColorAtom.reportObserved();
    return super.backColor;
  }

  @override
  set backColor(List value) {
    _$backColorAtom.context.conditionallyRunInAction(() {
      super.backColor = value;
      _$backColorAtom.reportChanged();
    }, _$backColorAtom, name: '${_$backColorAtom.name}_set');
  }

[shyndman]

hm, interesting that the dynamics are implicit here.

ok, next. what's your flutter --version?

[irvine5k]

@shyndman

Flutter 1.12.13+hotfix.5 • channel stable • https://github.com/flutter/flutter.git
Framework • revision 27321ebbad (4 weeks ago) • 2019-12-10 18:15:01 -0800
Engine • revision 2994f7e1e6
Tools • Dart 2.7.0

[shyndman]

k, give me a few

[shyndman]

OK, I have a reproduction! Nice.

Give me a few more. :)

[shyndman]

Alright, so stable and beta both produce incorrect output.

I have verified that two options fix the output:

1. Switch to Flutter dev or master channels OR
2. Downgrade your mobx dependencies to:
   mobx: ^0.3.6
mobx_codegen: '0.3.11'

@pavanpodila and I will introduce tests and a better process to make sure this doesn't happen again. Sorry about that.

[irvine5k]

No problem, @shyndman.

Thanks for your time.

[shyndman]

After a bit of research, I believe this to be the issue: dart-lang/build#2528

[shyndman]

Update: Heard back from the Dart folks, and I'm going to take a stab at fixing this in the build_resolvers library over the next couple days.

[irvine5k]

@shyndman Any news?

This bug occurred with another classes and was reported in community, unfortunately I can't describe how to reproduce it, seems kinda random.

And it's not the first time that I see like it in the Flutterando community. I asked him(member of community that is struggling with this problem) to contribute in this issue but apparently he's not gonna to do it.

Maybe this "Category" is using dart:ui in its members but we need investigate if there's other classes with the same problem.

There's any "workaround" further this below?

Switch to Flutter dev or master channels OR
Downgrade your mobx dependencies to:
mobx: ^0.3.6
mobx_codegen: '0.3.11'

[shyndman]

Hi @irvine5k,

No progress on build_resolvers yet. I'm going to look soon.

Is this the Category class from the Flutter framework? If so, then yes, it's the same problem.

[irvine5k]

Hi @irvine5k,

No progress on build_resolvers yet. I'm going to look soon.

Is this the Category class from the Flutter framework? If so, then yes, it's the same problem.

According him it's a class generated by Moor

Versions:

flutter_mobx 0.3.6
mobx 0.4.0+1
mobx_codegen 0.4.0+1
build_runner 1.7.3

[shyndman]

Thanks for the info.

I believe this is a whole other problem, and one that I've seen before — build's inability to analyze the source code of another file generated via build. mobx_codegen can't actually see the Category class, so it resolves to dynamic.

That said, I'm not a build expert. Let me verify that this is indeed the case, and if so, we can start looking into how to fix it.

[irvine5k]

Thanks for the info.

I believe this is a whole other problem, and one that I've seen before — build's inability to analyze the source code of another file generated via build. mobx_codegen can't actually see the Category class, so it resolves to dynamic.

That said, I'm not a build expert. Let me verify that this is indeed the case, and if so, we can start looking into how to fix it.

Thanks for your response @shyndman and your attention for this issue. I'll reporting more bugs and helping with I can.

Let me know about any evolution with this issue, so I can tell to the Flutterando's community.

[shyndman]

Sent a pull over to the build project which should resolve dart:ui problems if accepted.
dart-lang/build#2603

[shyndman]

Pull merged. We're almost there.

[shyndman]

Alright, build_resolvers is published as version 1.3.2. I'm putting together a PR right now to set it as our minimum version in mobx_codegen.

[irvine5k]

Great news o/