Backup: Add namespace versioning to Helper_Script_Manager and other classes

[pypt]

Add class versioning using PHP namespaces, to make sure that the plugin always loads the expected version of a class.

Proposed changes:

When two or more plugins are installed that contain a class with the same name (e.g. the main Jetpack plugin and the Jetpack VaultPress Backup plugin both ship Automattic\Jetpack\Backup\Helper_Script_Manager class), the Jetpack autoloader #34297 (comment), and under certain circumstances it might even decide to load an older version of the class.

Specifically, we had issues with the Jetpack VaultPress Backup plugin loading an older version of the Helper_Script_Manager class using the newer code, in which case an abspath property in Helper_Script_Manager::install_helper_script() (#34297) wasn't always returned.

• p1703028095475669-slack-CS8UYNPEE

To avoid that behavior, and always load the exact same version of the class that has been shipped with the plugin, we're adding simple namespace-based versioning to Helper_Script_Manager, backup plugin, and other related code.

All of the classes that make up the package/plugin got moved to either the Automattic\Jetpack\Backup\V0001 or the Automattic\Jetpack\Transport_Helper\V0001 namespace. Code that uses said classes refer to them using the versioned namespace (e.g. Automattic\Jetpack\Backup\V0001\Helper_Script_Manager::install_helper_script(), so that once the plugin gets installed, it always loads and uses a specific version of its dependencies (and not an older/newer one, which it might be incompatible with).

Older versions of the Jetpack plugins don't use these namespaces (e.g. they refer to the Helper_Script_Manager class as Automattic\Jetpack\Backup\Helper_Script_Manager), so if the plugin with versioned namespaces gets installed together with an older plugin without those, both should work fine.

If we ever need to change the plugin, the process is somewhat cumbersome yet straightforward:

1. Do the changes that you need;
2. Search for V0001, replace it with V0002 everywhere.

to make sure that older versions of the plugin load and use the V0001 version of the relevant code, and the newer versions use V0002.

Relevant discussions:

• peaFOp-2ar-p2
• Backup: Rewrite Helper_Script_Manager class, add tests #34297 (comment)

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

peaFOp-2ar-p2

Does this pull request change what data or activity we track or use?

No.

Testing instructions:

Just like with #34297, run a Jetpack VaultPress Backup backup without credentials set up, so that the tool is then forced to upload the helper script via Jetpack API and thus trigger this code.

Make sure that the abspath property gets always returned in the install_helper_script() results.

Also, test with multiple versions/forms of various Jetpack plugins installed, e.g. the newer Jetpack VaultPress Backup plugin (with this patch), and the older main Jetpack plugin (without this patch); make sure that you still always get the abspath back.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the modify/backup-helper-script-manager-class-versioning branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack modify/backup-helper-script-manager-class-versioning
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

The e2e test report can be found here. Please note that it can take a few minutes after the e2e tests checks are complete for the report to be available.

---

Once your PR is ready for review, check one last time that all required checks appearing at the bottom of this PR are passing or skipped.
Then, add the "[Status] Needs Team Review" label and ask someone from your team review the code. Once reviewed, it can then be merged.
If you need an extra review from someone familiar with the codebase, you can update the labels from "[Status] Needs Team Review" to "[Status] Needs Review", and in that case Jetpack Approvers will do a final review of your PR.

---

Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

• WordPress.com Simple releases happen daily.
• WoA releases happen weekly.
• Releases to self-hosted sites happen monthly. The next release is scheduled for January 9, 2024 (scheduled code freeze on January 8, 2024).

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

---

Backup plugin:

• Next scheduled release: February 6, 2024.
• Scheduled code freeze: January 29, 2024.

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

---

Protect plugin:

• Next scheduled release: February 6, 2024.
• Scheduled code freeze: January 29, 2024.

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

---

Migration plugin:

• Next scheduled release: February 6, 2024.
• Scheduled code freeze: January 29, 2024.

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[anomiex]

A quick opengrok search didn't turn up anything outside of the monorepo referring to the namespaces being changed, so 🤞 hopefully it won't break Simple.

I didn't review much beyond that and the few notes inline.