Label package:js as "legacy"

[srujzs]

Now that we have dart:js_interop and dart:js_interop_unsafe, we should point users to these libraries instead. This can go as part of the README in package:js (or maybe somewhere on pub?). This does not mean this library is deprecated and users need to migrate over. That will be done at some future date that is not yet known.

This also aligns us with some of the changes to mark libraries as Web (Legacy) on https://api.dart.dev/stable/3.2.4/index.html.

[parlough]

As a sort of related note, I've updated DartPad to provide a diagnostic on usages of dart:js to suggest users migrate. I'll be doing the same for package:js and dart:js_util soon, likely alongside the 3.3 release.

[kevmoo]

@parlough – do we want to do a one-off in dartpad, or just use hint/lints in the analyzer?

[parlough]

@parlough – do we want to do a one-off in dartpad, or just use hint/lints in the analyzer?

Well it's not necessarily one-off as I previously added general support for deprecating packages that we want to drop as well as core libraries we don't support. However, if an analyzer warning or lint is added, we can easily switch over to that for versions of the SDK that support it. I'd be happy to help implement the lint if that's the desired direction!

A bit separate of a discussion as it's about the core libraries, but rather than a lint, I personally prefer an opt-in mode that the analyzer and web compilers can use to switch to an SDK outline without these libraries (#54347). That way they don't even show up in completion suggestions.

[parlough]

Duplicate of #54792

I'm going to close this in favor of #54792 which outlines a specific path for doing this (a pub release with readme update).

Feel free to reopen if you think this issue is different enough. Thanks!