Editor: Ensure that the block editor can be used on the page post type.

Additionally, add a notice for when you are editing the "latest posts" page.

Fixes #45537.

Props cameronjonesweb, swissspidy, hannahmalcolm, Fantasy1125, ArnaudBan, grantmkin, youknowriad, knutsp, SergeyBiryukov, audrasjb, whyisjake. 

Built from https://develop.svn.wordpress.org/trunk@51116


git-svn-id: http://core.svn.wordpress.org/trunk@50725 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/edit-form-blocks.php

@@ -313,6 +313,10 @@ $script = sprintf(
 );
 wp_add_inline_script( 'wp-edit-post', $script );
 
+if ( (int) get_option( 'page_for_posts' ) === (int) $post->ID ) {
+	add_action( 'admin_enqueue_scripts', '_wp_block_editor_posts_page_notice' );
+}
+
 require_once ABSPATH . 'wp-admin/admin-header.php';
 ?>
 

wp-admin/includes/post.php

@@ -2134,11 +2134,6 @@ function use_block_editor_for_post( $post ) {
 		return false;
 	}
 
-	// The posts page can't be edited in the block editor.
-	if ( absint( get_option( 'page_for_posts' ) ) === $post->ID && empty( $post->post_content ) ) {
-		return false;
-	}
-
 	$use_block_editor = use_block_editor_for_post_type( $post->post_type );
 
 	/**

wp-admin/includes/template.php

@@ -2674,3 +2674,20 @@ function wp_star_rating( $args = array() ) {
 function _wp_posts_page_notice() {
 	echo '<div class="notice notice-warning inline"><p>' . __( 'You are currently editing the page that shows your latest posts.' ) . '</p></div>';
 }
+
+/**
+ * Output a notice when editing the page for posts in the block editor (internal use only).
+ *
+ * @ignore
+ * @since 5.8.0
+ */
+function _wp_block_editor_posts_page_notice() {
+	wp_add_inline_script(
+		'wp-notices',
+		sprintf(
+			'wp.data.dispatch( "core/notices" ).createWarningNotice( "%s", { isDismissible: false } )',
+			__( 'You are currently editing the page that shows your latest posts.' )
+		),
+		'after'
+	);
+}

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8-alpha-51115';
+$wp_version = '5.8-alpha-51116';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.