Using Colors.black as a primarySwatch causes an opaque error

[johnpryan]

Using Colors.black as a primarySwatch causes an opaque error

1. open https://dartpad.dev/b6409e10de32b280b8938aa75364fa7b
2. change primarySwatch from Colors.blue to Colors.black
3. click Run
4. Observe the app stops working without analysis errors or console output

Here's the error in the javascript console:

Uncaught Error: Assertion failed: file:///Users/brettmorgan/Documents/GitHub/dart-services/flutter/packages/flutter/lib/src/widgets/framework.dart:2687:20
_debugCurrentBuildTarget == context
is not true
    at Object.throw_ [as throw] (storage.googleapis.com/compilation_artifacts/2.10.0/dart_sdk.js:4328)
    at Object.assertFailed (storage.googleapis.com/compilation_artifacts/2.10.0/dart_sdk.js:4275)
    at storage.googleapis.com/compilation_artifacts/2.10.0/flutter_web.js:318195
    at framework.BuildOwner.new.buildScope (storage.googleapis.com/compilation_artifacts/2.10.0/flutter_web.js:318199)
    at RenderObjectToWidgetAdapter.new.attachToRenderTree (storage.googleapis.com/compilation_artifacts/2.10.0/flutter_web.js:306959)
    at binding$.WidgetsFlutterBinding.new.attachRootWidget (storage.googleapis.com/compilation_artifacts/2.10.0/flutter_web.js:306827)
    at storage.googleapis.com/compilation_artifacts/2.10.0/flutter_web.js:306822
    at internalCallback (storage.googleapis.com/compilation_artifacts/2.10.0/dart_sdk.js:23761)

[johnpryan]

Related to #1649

[domesticmouse]

I'm curious why this code doesn't throw a type error during analysis. primarySwatch is typed as MaterialColor and Colors.black is typed as a Color.

[domesticmouse]

As of Flutter 1.25 this is much less of an issue. The analyzer issues an error.

[johnpryan]

Type checking FTW. Now I'm thinking that the problem is with printing assertion failures:

import 'package:flutter/material.dart';
void main() {
  assert(1 == 2);
}

This prints an error in the javascript console, but not the DartPad console.

[RedBrogdon]

One of the areas of tech debt we really need to address is error reporting in general. If this can be bundled into some of the DartPad work we've already talked about in the next few months (by you or anyone else), it'd be worth the investment.

[johnpryan]

Another case where this shows up:

import 'package:flutter/material.dart';

void main() {
  runApp(const ListViewApp());
}

class ListViewApp extends StatelessWidget {
  static const itemCount = 10;
  const ListViewApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(),
        body: ListView.builder(
          // itemCount: itemCount, // uncomment to fix!
          itemBuilder: (context, idx) {
            assert(idx < itemCount);
            return ListTile(
              title: Text('$idx'),
            );
          },
        ),
      ),
    );
  }
}

We should be displaying something more user-friendly instead of crashing. Running locally shows a red widget of death:

but in DartPad we get a stack trace in the JavaScript console and Script error. in the DartPad console:

Uncaught Error: Assertion failed: file:///Users/brettmorgan/Documents/GitHub/dart-services/flutter-sdk/packages/flutter/lib/src/rendering/object.dart:1532:12
_debugCanPerformMutations
is not true
    at Object.throw_ [as throw] (dart_sdk.js:5037)
    at Object.assertFailed (dart_sdk.js:4976)
    at view.RenderView.new.markNeedsLayout (flutter_web.js:195881)
    at view.RenderView.new.set configuration [as configuration] (flutter_web.js:442310)
    at binding$.WidgetsFlutterBinding.new.handleMetricsChanged (flutter_web.js:327613)
    at binding$.WidgetsFlutterBinding.new.handleMetricsChanged (flutter_web.js:325887)
    at Object.invoke (dart_sdk.js:175219)
    at _engine.EnginePlatformDispatcher.__.invokeOnMetricsChanged (dart_sdk.js:156971)
    at _engine.DomRenderer.new.[_metricsDidChange] (dart_sdk.js:140844)
    at Object._checkAndCall (dart_sdk.js:5242)
    at Object.dcall (dart_sdk.js:5247)
    at VisualViewport.<anonymous> (dart_sdk.js:100617)

[johnpryan]

Tracking this issue here: #1966