Remove `dart:js` from dart2wasm

[srujzs]

This library was added to support allowInterop. All of the methods throw and importing dart:js returns a static error. However, doing conditional imports e.g. if (dart.library.js) succeeds in dart2wasm, because the library still exists in libraries.json. Since allowInterop is now no longer defined in dart:js, we should just remove this library altogether from the platform.

[mkustermann]

/cc @osa1 Could we disallow importing dart:js just like we (after cl/368343) disallow importing dart:ffi (until we remove dart:js entirely)?

[srujzs]

There's already a static error we've added to disallow importing dart:js in dart2wasm:

sdk/pkg/_js_interop_checks/lib/js_interop_checks.dart

Line 541 in 2250404

if (_disallowedInteropLibrariesInDart2Wasm

[osa1]

Do we need to make any changes in Flutter for this? I've created an SDK CL to remove dart:js from the platform: https://dart-review.googlesource.com/c/sdk/+/368642.

[mkustermann]

Do we need to make any changes in Flutter for this? I've created an SDK CL to remove dart:js from the platform: https://dart-review.googlesource.com/c/sdk/+/368642.

Maybe this issue also includes dart:js_util (which we currently use internally in the implementation of dart:js_interop)

[srujzs]

I don't think Flutter uses dart:js anywhere. I'm not sure why your CL results in package:js complaining about exporting dart:_js_annotations now. That should be tangential but I'll have to take a deeper look.

Maybe this issue also includes dart:js_util (which we currently use internally in the implementation of dart:js_interop)

There are a few migrations that need to happen in Flutter and elsewhere (as well as migrating our own implementation of dart:js_interop like you note) before package:js and dart:js_util can be removed from dart2wasm. I'd expect it to be harder than removing dart:js.

[sigmundch]

FYI - we run again into this issue. I've created https://dart-review.googlesource.com/c/sdk/+/380583 to attempt again. It's very similar to the change @osa1 created a while back, but I reduced the scope a bit to see if we can make it easier to land.

Do you recall @osa1 what issues you ran into (aside from the bot failures that the CL shows?)

Alternatively, we could use the "supports: false" line in the libraries.json to start incrementally (I'll prepare a change to do so for dart:js_util, since we still have cases where we load code from it).