Autoloader: Avoid a PHP warning when an empty string is passed to is_directory_plugin().

[dd32]

Autoloader: Avoid a PHP warning when an empty string is passed to is_directory_plugin().

Example Warning: strpos(): Offset not contained in string.

Changes proposed in this Pull Request:

• Avoids a PHP warning when an empty string is passed to is_directory_plugin().

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

No.

Testing instructions:

I'm not really sure how this has happened, but on WordPress.org get_option( 'active_plugins' ) returns '' (an empty string) on some sites. I don't know if that's expected or not, but I suspect it only happens on sites that have never had a plugin activated on it directly, only through Network-activated plugins.

It causes get_active_plugin_paths() https://github.com/Automattic/jetpack/blob/master/packages/autoloader/src/class-plugins-handler.php#L48-L52 to have array( '' ) as it's $plugin_slugs value, which seems like it might be expected due to it casting the option result to an array..
I've included a unit test which covers at least the result of this.

An alternative patch could have been to perform an array_filter() over $plugin_slugs first in get_active_plugin_paths() but this seemed more defensive.

Proposed changelog entry for your changes:

• N/A

[jetpackbot]

Thank you for the great PR description!

When this PR is ready for review, please apply the [Status] Needs Review label. If you are an a11n, please have someone from your team review the code if possible. The Jetpack team will also review this PR and merge it to be included in the next Jetpack release.

E2E results is available here (for debugging purposes): https://jetpack-e2e-dashboard.herokuapp.com/pr-16442

Scheduled Jetpack release: August 4, 2020.
Scheduled code freeze: July 28, 2020

Generated by 🚫 dangerJS against 4860b7e

[kraftbj]

Thanks for the patch. We can't duplicate this on a brand new multisite with no local plugins activated in our initial look, so might just be some odd legacy w.org stuff going on.

[kbrown9]

This looks good to me. Thanks for the fix and the unit test!

[dd32]

We can't duplicate this on a brand new multisite with no local plugins activated in our initial look, so might just be some odd legacy w.org stuff going on.

I've never known the option to not contain an array either, so I really do suspect it's some ancient effect of some kind.

I suspect it may have predated the $default_value 2nd-argument to get_option() which caused the options to be set to an empty string in the first place, potentially even a bug only in a non-released version of WP (ie. trunk) which WordPress.org ran.

[kraftbj]

Makes sense. Either way, 40 minutes without any warnings on w.org, so that's an approved review from me. Thanks for the assist!

[jeherve]

Cherry-picked to branch-8.7 in 9c1c811

[jeherve]

Updated the release branch to a new version of Jetpack Autoloader with that fix in 461b349