jetpack-mu-wpcom: Code Block / Improve safety when modifying modules actions

[sirreal]

Proposed changes:

The Code block modifies the script modules actions in order to insert its own action between some of the Core actions.

This change attempts to abort and restore the Core actions in case they cannot be removed as expected.

Follow-up to #45181

The block enqueues an empty "dummy" module in order to add modules to the importmap. Without more invasive tools like Reflection, this method works. In order to avoid actually printing the empty module script tag and requesting the empty JavaScript file, an action is inserted to dequeue and re-enqueue the empty module at appropriate times. This requires moving the script modules printing actions so that the module can be dequeued and enqueued in the right order.

If, for some reason, there's a problem removing the existing actions, this process should abort and attempt to restore the previous behavior. This will result in the empty module being requested, which is harmless.

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

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

No.

Testing instructions:

The Core modules actions can be moved like this:

add_action(
	'after_setup_theme',
	function () {
		foreach ( array( 'wp_head', 'wp_footer', 'admin_print_footer_scripts' ) as $hook ) {
				remove_action( $hook, array( wp_script_modules(), 'print_import_map' ) );
				remove_action( $hook, array( wp_script_modules(), 'print_enqueued_script_modules' ) );
				remove_action( $hook, array( wp_script_modules(), 'print_script_module_preloads' ) );
				add_action( $hook, array( wp_script_modules(), 'print_import_map' ), 8 );
				add_action( $hook, array( wp_script_modules(), 'print_enqueued_script_modules' ), 8 );
				add_action( $hook, array( wp_script_modules(), 'print_script_module_preloads' ), 8 );
		}
	},
	80
);

If this is done on trunk, the core modules actions fail to be removed correctly so run twice. The result is duplicate script tags and preloads. This PR fixes that so that there are no duplicate tags. In both cases, the empty module script tag is printed (harmless).

[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 WoA dev 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 (WordPress.com Site Helper), and enable the wpcom-code-block/improve-actions-safety branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack-mu-wpcom-plugin wpcom-code-block/improve-actions-safety

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]

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/packages/jetpack-mu-wpcom/src/features/wpcom-blocks/code/class-code-block.php	0/192 (0.00%)	0.00%	3 ❤️‍🩹

Full summary · PHP report

[dmsnell]

was this a triggered bug in practice? did it occur because of other code messing with those filters?

[sirreal]

was this a triggered bug in practice? did it occur because of other code messing with those filters?

I was able to contrive a situation where this occurred by messing with the filters. It never happened on a real site, but to my knowledge the Code block with this logic was only only deployed on 3 real sites. It's hard to know whether this would be common or not.

[sirreal]

I need to double check the order that script modules use in Core. I think these conditions should be reversed so that the last action is removed first. Then, if it needs to be restored, it would be put back at the end of the filter list. That potentially helps to preserve the original ordering.