Potential fatal error when autoloading non-existent Composer class

[aaemnnosttv]

Bug Description

There have been a few reports of fatal errors since the last release 1.98.0

PHP Warning:  require_once(/var/www/html/web/wp-content/plugins/google-site-kit/third-party/vendor/composer/InstalledVersions.php): Failed to open stream: No such file or directory in /var/www/html/web/wp-content/plugins/google-site-kit/includes/loader.php on line 34
PHP Fatal error:  Uncaught Error: Failed opening required '/var/www/html/web/wp-content/plugins/google-site-kit/third-party/vendor/composer/InstalledVersions.php' (include_path='.:/usr/share/php') in /var/www/html/web/wp-content/plugins/google-site-kit/includes/loader.php:34

• https://wordpress.org/support/topic/version-4-4-3-causes-fatal-error-with-google-site-kit-1-98-0/

This dates back to a change made in #3830 which was later undone in #1146.

The initial guard which prevented this from happening used the required class name to only load Site Kit classes by checking the full class name. This had to be removed in #1146 when certain vendor-provided polyfill classes also needed to be autoloaded. Ultimately, the problem is that a non-existent class is attempted to be required.

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Acceptance criteria

• The Site Kit autoloader should not throw any errors due to non-existent files or classes

Implementation Brief

• Merge Update autoloader to avoid loading non-existing classes #6888

Test Coverage

• No changes

QA Brief

• Add the following snippet to a plugin or theme to reproduce the error on 1.98.0

add_action( 'plugins_loaded', array( '\Composer\InstalledVersions', 'getInstalledPackages' ) );

• Once merged, the error should no longer happen on develop

Changelog entry

• Fix a potential error when attempting to autoload a class from a non-existent file.

[eugene-manuilov]

IB ✔️

[wpdarren]

QA Update: ✅

Verified

On 1.98.0 the PHP error message appeared in my logs.

I switched to the main branch and navigated around Site Kit and left it for 10 minutes and no further errors appeared.