Fix Gutenberg plugin assuming its directory is named "gutenberg" (#78705)

* Fix broken Demo menu link when plugin directory is not named "gutenberg"

The Demo submenu was registered without a callback, so add_submenu_page()
never registered a page hook. In wp-admin/menu-header.php the menu URL then
falls back to a file_exists() heuristic on WP_PLUGIN_DIR/{slug}, which only
matches when the plugin folder is literally named "gutenberg". Running from
gutenberg-build/ (or any other directory) makes the check fail, producing a
broken /wp-admin/gutenberg link that 404s.

Pass a no-op callback so the page hook is registered and the link becomes
independent of the plugin directory name. The admin_init redirect still runs
first, so the callback body never executes.

Fixes #76473

* Fix plugin deactivation when plugin directory is not named "gutenberg"

The version-check failure path hardcoded the plugin slug
'gutenberg/gutenberg.php', so deactivate_plugins() failed to match and
the plugin kept running when installed under a different directory name
(e.g. gutenberg-build/). Resolve the slug from the main file via
plugin_basename( __FILE__ ) so deactivation works regardless of folder name.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* Fix collaboration activation hook when plugin directory is not named "gutenberg"

The activation hook was registered with the hardcoded slug
'activate_gutenberg/gutenberg.php', so it never fired when the plugin was
installed under a different directory name (e.g. gutenberg-build/), leaving
the wp_collaboration_enabled default option unset on activation. Build the
hook name from the main file's basename via plugin_basename() so it matches
the actual slug WordPress fires regardless of folder name.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: t-hamano <wildworks@git.wordpress.org>
Co-authored-by: ramonjd <ramonopoly@git.wordpress.org>
Co-authored-by: 3kori <r1k0@git.wordpress.org>
Co-authored-by: peterwilsoncc <peterwilsoncc@git.wordpress.org>

Author: 4 people

gutenberg.php

@@ -27,7 +27,7 @@ function gutenberg_wordpress_version_notice() {
 	printf( __( 'Gutenberg requires WordPress %s or later to function properly. Please upgrade WordPress before activating Gutenberg.', 'gutenberg' ), GUTENBERG_MINIMUM_WP_VERSION );
 	echo '</p></div>';
 
-	deactivate_plugins( array( 'gutenberg/gutenberg.php' ) );
+	deactivate_plugins( array( plugin_basename( __FILE__ ) ) );
 }
 
 /**

lib/compat/wordpress-7.1/collaboration.php

@@ -242,7 +242,7 @@ function gutenberg_set_collaboration_option_on_activation() {
 		update_option( 'wp_collaboration_enabled', '1' );
 	}
 }
-add_action( 'activate_gutenberg/gutenberg.php', 'gutenberg_set_collaboration_option_on_activation' );
+add_action( 'activate_' . plugin_basename( dirname( __DIR__, 3 ) . '/gutenberg.php' ), 'gutenberg_set_collaboration_option_on_activation' );
 
 /**
  * Modifies the post list UI and heartbeat responses for real-time collaboration.

lib/init.php

@@ -27,7 +27,8 @@ function gutenberg_menu() {
 		__( 'Demo', 'gutenberg' ),
 		__( 'Demo', 'gutenberg' ),
 		'edit_posts',
-		'gutenberg'
+		'gutenberg',
+		'__return_null',
 	);
 
 	if ( current_user_can( 'edit_posts' ) ) {