Add dart=3.7 pragmas to protobuf lib code

[osa1]

With this we can finally have the same formatting in the internal version and the open source version.

This also syncs some simple changes from internal to the open source.

With this the library code is almost identical internally and in the open source. There are still a few changes that need to be synced (enum names, reflection callbacks), which I'll do separately.

cl/832251175 adds the pragmas internally and reformats internal code. Also includes some trivial syncs from this version to the internal.

To avoid bumping SDK dependency from 3.7 to 3.10, we format with 3.7 instead of 3.10. However note that SDK 3.9 cannot be used to format the repo as it has a bug and the formatter in 3.9 does not respect the @dart=... lines.

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:protobuf	5.2.0	ready to publish	protobuf-v5.2.0
package:protoc_plugin	25.0.0	ready to publish	protoc_plugin-v25.0.0

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

[natebosch]

This is not safe to land. This breaks compatibility with older SDKs. It's troubling that we don't have CI set up to catch this.

We must either pin to language version 3.7 or change the constraint in the pubspec

environment:
  sdk: ^3.10.0

[osa1]

Why 3.7?

Why can't users who can't upgrade to 3.10 use the older version of the library?

The formatter in 3.9 doesn't respect the // @dart=... lines, that's why I waited until 3.10 to add these lines. We can add 3.7 as long as we always format with 3.10 or newer.

Why do you want to support 3.7 @natebosch?

You're right that if we have a min. supported version policy there should be checks to enforce it.

I've been maintaining this library for the past 3.5 years and I'm not aware of any such policy.

[sigurdm]

Why can't users who can't upgrade to 3.10 use the older version of the library?

They can use the old version, but they can also accidentally get this new one by pub upgrade which is unfortunate, as it won't work.

In other words the @dart= pragmas should not be higher than the minimum allowed by the sdk constraint at https://github.com/google/protobuf.dart/blob/master/protobuf/pubspec.yaml#L9.

[osa1]

Good point, we should make sure the pubspec is in sync with the @dart comments.

What should be the oldest supported SDK version? Do we have a policy in ecosystem packages for the min. supported version?

[sigurdm]

I don't think we have a policy. The lower bound cannot be lower than the target of the generated code. So I guess it would make sense to make it ^3.10.0.

That means older darts won't benefit from the new protobuf improvements, but I think that is acceptable.

[natebosch]

I don't think we should land this without some mechanism to prevent incorrect updates. Maybe it's sufficient to add a CI run on the lowest supported SDK?