UnmodifiableMapMixin and others aren't Dart3-ready

[oprypin]

UnmodifiableMapMixin should become a mixin or mixin class. Otherwise it is not ready for use with Dart 3 / prefer_mixin.
All usages of it are expected to be within a with clause.

Others that I noticed are NonGrowableListMixin, UnmodifiableSetMixin

[lrhn]

https://dart-review.googlesource.com/c/sdk/+/288240 should hopefully land soon-ish.

[oprypin]

Is that related? This is about 'package:collection'

[lrhn]

(Already updated the URL, pasted the wrong one originally.)

[oprypin]

🙂 I think it's still different - 'dart:collection' vs 'package:collection'

[lrhn]

Argh. My bad. Wrong issue tracker entirely. (Naming footgun!)

Yes, yes they should.

[oprypin]

Ping on this issue. I think this is high priority to resolve and make a release of this library ahead of Dart 3.

Also cc @mit-mit @devoncarew

[lrhn]

There is technically no reason to eagerly change anything, since pre-3.0 code classes can still be used as mixins without the mixin modifier. As long as this package's min-SDK is 2.18.0, mixin in should keep workin.

It's only an issue if someone tries to interpret the pre-3.0 code as post-3.0 code, ignoring the languge-version of the pubspec, which is not a safe thing to do since 3.0 is a breaking change for the language.
(And I believe the case where that was happening is no longer an issue, so we're not in any rush to release a 3.0 version.)

It's another issue that migrating the package to 3.0 properly should, rightfully, mean a major version increment.
Those are harder to release.

[dannnnthemannnn]

Hey all, I'm trying to use collections.dart and am getting errors like:

packages/collection/src/boollist.dart:231:50:
Error: The class 'NonGrowableListMixin' can't be used as a mixin because it isn't a mixin class nor a mixin.
class _NonGrowableBoolList extends BoolList with NonGrowableListMixin {
This is pulled in via transitive dependencies.

My dart version:

dart --version
Dart SDK version: 3.4.0 (stable) (Mon May 6 07:59:58 2024 -0700) on "macos_arm64"

I see this package says its SDK is ^3.1 in the pubspec.yaml.

Am I doing something wrong or is there a way to get this to continue working? I am using the dart associated with the latest version of flutter

My build command is: dart run build_runner build --output=build

[lrhn]

Are you using the 1.19.0-wip version, which hasn't been released (or completed) yet?
The most recent release is 1.18.0, which uses SDK 2.18.

[dannnnthemannnn]

Ah I am using 1.18. So its not possible currently to use dart:collection with the current dart version? Curious how does flutter work when the current packaged dart version with flutter stable is 3.4?

[lrhn]

You should be able to use package:collection 1.18 with any SDK that supports language version 2.18. All 3.X SDKs supports that.

If you do so, you should not get any error.
Pre-3.0 classes with no superclass can be used as mixins, both by pre- and post-3.0 code.

If it cannot, we have a bug.

I cannot reproduce the issue. Using tip-of-tree SDK, in a fresh dart package (dart create coltest) with an SDK version of ^3.3.0 and dependency collection: 1.18.0, the following code has no error:

import "dart:collection";
import "package:collection/collection.dart";

abstract class C extends ListBase<int> with NonGrowableListMixin<int> {}

Any chance you can show an entire compilable file that has the error, and/or check the language version of package:collection in .dart_tool/package_config.json?

[dannnnthemannnn]

I am building using build runner/dart2js. The language version in collection says

{
  "name": "collection",
  "rootUri": "file:///Users/dannyfranklin/.pub-cache/git/collection-d51223f93e109408666606fbb13a37b79a1ec2c2/",
  "packageUri": "lib/",
  "languageVersion": "3.0"
},

I am building using flutter pub run build_runner build --output=build
and my build.

My build.yaml

targets:
  $default:
    sources:
      - "$package$"
      - "node/**"
      - "lib/**"
      - "js/**"
    builders:
      build_node_compilers|entrypoint:
        generate_for:
        - node/**
        options:
          compiler: dart2js
          # List any dart2js specific args here, or omit it.
          dart2js_args:
            - -O0
      json_serializable:
        options:
          explicit_to_json: true

My pubspec env:

environment:
  sdk: ">=2.18.0 <3.0.0"