Fix a case where wp_rand is undefined.

[zinigor]

Fixes a fatal error that can occur when wp_rand is called too early.

Proposed changes:

• Adds a check for the wp_rand function existence, replacing it with rand if necessary.

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?

Testing instructions:

• Add this action to your test site:

add_action( 'plugin_loaded', function() {
    if ( class_exists( '\Automattic\Jetpack\A8c_Mc_Stats' ) ) {
        $stats = new \Automattic\Jetpack\A8c_Mc_Stats();
        $stats->add( 'bogus', 'stat' );
        error_log( print_r( $stats->get_stats_urls(), true ) );
    }
} );

• Observe fatal errors in regular usage.
• Use this PR.
• Observe no fatals, instead only correct stat URLs in the logs.

[github-actions]

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[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 fix/mc-stats-wp-rand-undefined branch.

  • For jetpack-mu-wpcom changes, also add define( 'JETPACK_MU_WPCOM_LOAD_VIA_BETA_PLUGIN', true ); to your wp-config.php file.

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

  bin/jetpack-downloader test jetpack fix/mc-stats-wp-rand-undefined
  

  bin/jetpack-downloader test jetpack-mu-wpcom-plugin fix/mc-stats-wp-rand-undefined
  

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

[kraftbj]

Looks good to me.

[anomiex]

Personally I think the fatal probably indicates a problem in the caller, calling this too early. But it looks like it should do what's intended to work around problematic callers instead.