Add a mu-plugin loader that loads a specific version of a plugin if r…

…equired. (#561)

* Add a mu-plugin loader that loads a specific version of a plugin if required.

* Run the check on both locally-active plugins and network-activated plugins

Gutenberg shows up in both sometimes, so we should check and remove from both.

* Add Pattern Creator as incompatible with GB

* Don't filter the active plugins on the plugins management page, to avoid the filtered array being saved and becoming un-filtered.

---------

Co-authored-by: Kelly Dwan <[email protected]>

mu-plugins/plugin-tweaks/incompatible-plugins.php

@@ -0,0 +1,88 @@
+<?php
+
+namespace WordPressdotorg\MU_Plugins\Plugin_Tweaks\IncompatiblePlugins;
+
+defined( 'WPINC' ) || die();
+
+// Don't run this on the plugins.php page, as we don't want to operate on filtered options.
+if ( defined( 'WP_ADMIN' ) && WP_ADMIN && str_contains( $_SERVER['REQUEST_URI'] ?? '', '/plugins.php' ) ) {
+	return;
+}
+
+/**
+ * Plugin config.
+ *
+ * Each item in the array contains a plugin to check (`check`), and a plugin
+ * that should be deactivated (`from`) in favor of another plugin (`to`).
+ */
+const PLUGINS = [
+	[
+		// Blocks Everywhere: Uses private/unstable APIs,
+		// which are blocked after GB 16.8.
+		'check' => 'blocks-everywhere/blocks-everywhere.php',
+		'from'  => 'gutenberg/gutenberg.php',
+		'to'    => 'gutenberg-16.8/gutenberg.php',
+	],
+	[
+		// Pattern Creator: Uses private/unstable APIs,
+		// which are blocked after GB 16.8.
+		'check' => 'pattern-creator/pattern-creator.php',
+		'from'  => 'gutenberg/gutenberg.php',
+		'to'    => 'gutenberg-16.8/gutenberg.php',
+	],
+];
+
+/**
+ * Check the above list of plugins, and filter the appropriate option.
+ *
+ * This needs to be done on plugin inclusion, as network-wide plugins are included immediately after mu-plugins.
+ */
+function filter_the_filters() {
+	$active_plugins          = (array) get_option( 'active_plugins', [] );
+	$active_sitewide_plugins = is_multisite() ? get_site_option( 'active_sitewide_plugins', [] ) : [];
+
+	foreach ( PLUGINS as $incompatible_plugin ) {
+		$check = $incompatible_plugin['check'];
+		$from  = $incompatible_plugin['from'];
+		$to    = $incompatible_plugin['to'];
+
+		// Check to see if the incompatible plugin is active first.
+		// Not using the functions that do this, as they're only loaded in wp-admin.
+		if (
+			! in_array( $check, $active_plugins, true ) &&
+			! isset( $active_sitewide_plugins[ $check ] )
+		) {
+			continue;
+		}
+
+		if ( in_array( $from, $active_plugins, true ) ) {
+			add_filter(
+				'option_active_plugins',
+				function( $plugins ) use ( $from, $to ) {
+					// Splice to retain load order, if it's important.
+					array_splice(
+						$plugins,
+						array_search( $from, $plugins, true ),
+						1,
+						$to
+					);
+					return $plugins;
+				}
+			);
+		}
+
+		if ( isset( $active_sitewide_plugins[ $from ] ) ) {
+			add_filter(
+				'site_option_active_sitewide_plugins',
+				function( $plugins ) use ( $from, $to ) {
+					$plugins[ $to ] = $plugins[ $from ];
+					unset( $plugins[ $from ] );
+
+					return $plugins;
+				}
+			);
+		}
+	}
+}
+
+filter_the_filters();

mu-plugins/plugin-tweaks/index.php

@@ -11,3 +11,4 @@
 
 require_once __DIR__ . '/wporg-internal-notes.php';
 require_once __DIR__ . '/stream.php';
+require_once __DIR__ . '/incompatible-plugins.php';