[PHP] option exclude backwards compatible proto files

[bshaffer]

For PHP all nested messages generate two classes, the current namespaced class and a file to support backwards compatibility with the previous non-namespaced files. There's also a class_alias call at the bottom of every nested message. See this PR from almost 4 years ago.

As been almost 4 years, these files are now more of a nuisance. I see three potential options here, ranked from least to most risky:

• Add a flag to tell protoc to not generate these files for PHP (opt-out, most conservative)
• Add a flag to tell protoc to generate these files for PHP (opt-in, could potentially break some very slow to upgrade users)
• Remove the backwards compatibility logic all together (as it's been throwing deprecation errors for almost four years, I feel comfortable with this solution)

I'm happy to give a PR a try any of these options are possible!

[haberman]

I think removing the backward compat logic is the way to go at this point.

Four years with deprecation warnings seems sufficient.

[bshaffer]

The only issue I can think of is for libraries like google-cloud-php, we wouldn't want to remove the class_alias code from proto files which currently have it. Not because we think it's needed, but because it would constitute a backwards-compatibility change. So what we could do is:

1. Only remove the old alias file (e.g. Nested_Message.php) but keep the class alias (e.g. the call to class_alias at the bottom of Nested\Message.php) for now
2. Add a flag (once again) for removing or adding the call to class_alias
3. Not care at all and we can handle it on our end :)

[terax6669]

since the latest release still outputs deprecated files...

grep 'is deprecated and will be removed in the next major release' -R path/to/proto -l | xargs rm'

[github-actions]

We triage inactive PRs and issues in order to make it easier to find active work. If this issue should remain active or becomes active again, please add a comment.

This issue is labeled inactive because the last activity was over 90 days ago.

[haberman]

We're making a breaking change release now. This is the perfect time to remove these deprecated files.