Stop generating `.packages`

[lrhn]

There is no need for a new SDK to generate a .packages file for itself. The only reason for having one is to support old third-party tools which have not started using the .dart_tool/package_config.json file yet.

We should identify any such tools blocking us from removing the .packages file, make sure they are updated, and then stop generating .packages files.

The sooner this is done, the better.

Would it be possible to stop generating the .packages file for Pub in SDK -dev builds? That should smoke out any remaining uses of the file. Maybe keep the feature available under a flag, so people really needing it can still get it that way?

[jonasfj]

ironically, pub might be one of the tools that depends on this file :D

Or put, differently: pub still expects the .packages file to be present when testing if dependencies are up-to-date (with pubspec.lock and pubspec.yaml).

I think we could:

1. Ensure that pub doesn't require the presence of .packages optional,
2. Add a --legacy-packages-file flag: Add flag controlling creation of .packages file. #2757
3. Send out a breaking change notification that .packages is going away.
4. Update docs: Migrate from .packages to package_config.json site-www#2777

[lrhn]

Another thing that we can do, before flipping the flag, is that every time a pub run of a globally activated package finds only a .packages file, it immediately generates a .dart_tool/package_config.json file too (maybe just blindly copying the data from the .packages file and adding language version 2.7 to every package).

[mit-mit]

@jonasfj is the first item in your checklist done now?

[mit-mit]

Also, can I suggest we add the --no-packages-file flag, and configure all our own tests to run with that, to see if we can shake out any unknown issues?

[sigurdm]

@jonasfj is the first item in your checklist done now?

Yes, this was done in: #2764

[mit-mit]

Hi @jonasfj we need to make progress on this; can we go ahead and add the --no-packages-file flag?

[sigurdm]

Hi @jonasfj we need to make progress on this; can we go ahead and add the --no-packages-file flag?

I'll start reviving the PR we have lying around.

[sigurdm]

Done in #2757