Fix metabox reordering

docs/reference-guides/data/data-core-edit-post.md

@@ -6,6 +6,18 @@ Namespace: `core/edit-post`.
 
 <!-- START TOKEN(Autogenerated selectors|../../../packages/edit-post/src/store/selectors.js) -->
 
+### areMetaBoxesInitialized
+
+Returns true if meta boxes are initialized.
+
+_Parameters_
+
+-   _state_ `Object`: Global application state.
+
+_Returns_
+
+-   `boolean`: Whether meta boxes are initialized.
+
 ### getActiveGeneralSidebarName
 
 Returns the current active general sidebar name, or null if there is no
@@ -351,6 +363,10 @@ _Returns_
 
 -   `Object`: Action object.
 
+### initializeMetaBoxes
+
+Initializes WordPress `postboxes` script and the logic for saving meta boxes.
+
 ### metaBoxUpdatesFailure
 
 Returns an action object used to signal a failed meta box update.

packages/edit-post/README.md

@@ -31,13 +31,10 @@ They can be found in the global variable `wp.editPost` when defining `wp-edit-po
 
 Initializes and returns an instance of Editor.
 
-The return value of this function is not necessary if we change where we
-call initializeEditor(). This is due to metaBox timing.
-
 _Parameters_
 
 -   _id_ `string`: Unique identifier for editor instance.
--   _postType_ `Object`: Post type of the post to edit.
+-   _postType_ `string`: Post type of the post to edit.
 -   _postId_ `Object`: ID of the post to edit.
 -   _settings_ `?Object`: Editor settings object.
 -   _initialEdits_ `Object`: Programmatic edits to apply initially, to be considered as non-user-initiated (bypass for unsaved changes prompt).

packages/edit-post/src/components/meta-boxes/index.js

@@ -6,7 +6,9 @@ import { map } from 'lodash';
 /**
  * WordPress dependencies
  */
-import { withSelect } from '@wordpress/data';
+import { useSelect, useRegistry } from '@wordpress/data';
+import { useEffect } from '@wordpress/element';
+import { store as editorStore } from '@wordpress/editor';
 
 /**
  * Internal dependencies
@@ -15,7 +17,44 @@ import MetaBoxesArea from './meta-boxes-area';
 import MetaBoxVisibility from './meta-box-visibility';
 import { store as editPostStore } from '../../store';
 
-function MetaBoxes( { location, isVisible, metaBoxes } ) {
+export default function MetaBoxes( { location } ) {
+	const registry = useRegistry();
+	const {
+		metaBoxes,
+		isVisible,
+		areMetaBoxesInitialized,
+		isEditorReady,
+	} = useSelect(
+		( select ) => {
+			const { __unstableIsEditorReady } = select( editorStore );
+			const {
+				isMetaBoxLocationVisible,
+				getMetaBoxesPerLocation,
+				areMetaBoxesInitialized: _areMetaBoxesInitialized,
+			} = select( editPostStore );
+			return {
+				metaBoxes: getMetaBoxesPerLocation( location ),
+				isVisible: isMetaBoxLocationVisible( location ),
+				areMetaBoxesInitialized: _areMetaBoxesInitialized(),
+				isEditorReady: __unstableIsEditorReady(),
+			};
+		},
+		[ location ]
+	);
+
+	// When editor is ready, initialize postboxes (wp core script) and metabox
+	// saving. This initializes all meta box locations, not just this specific
+	// one.
+	useEffect( () => {
+		if ( isEditorReady && ! areMetaBoxesInitialized ) {
+			registry.dispatch( editPostStore ).initializeMetaBoxes();
+		}
+	}, [ isEditorReady, areMetaBoxesInitialized ] );
+
+	if ( ! areMetaBoxesInitialized ) {
+		return null;
+	}
+
 	return (
 		<>
 			{ map( metaBoxes, ( { id } ) => (
@@ -25,14 +64,3 @@ function MetaBoxes( { location, isVisible, metaBoxes } ) {
 		</>
 	);
 }
-
-export default withSelect( ( select, { location } ) => {
-	const { isMetaBoxLocationVisible, getMetaBoxesPerLocation } = select(
-		editPostStore
-	);
-
-	return {
-		metaBoxes: getMetaBoxesPerLocation( location ),
-		isVisible: isMetaBoxLocationVisible( location ),
-	};
-} )( MetaBoxes );

packages/edit-post/src/index.js

@@ -14,7 +14,6 @@ import { store as interfaceStore } from '@wordpress/interface';
  */
 import './hooks';
 import './plugins';
-export { store } from './store';
 import Editor from './editor';
 
 /**
@@ -63,11 +62,8 @@ export function reinitializeEditor(
 /**
  * Initializes and returns an instance of Editor.
  *
- * The return value of this function is not necessary if we change where we
- * call initializeEditor(). This is due to metaBox timing.
- *
  * @param {string}  id           Unique identifier for editor instance.
- * @param {Object}  postType     Post type of the post to edit.
+ * @param {string}  postType     Post type of the post to edit.
  * @param {Object}  postId       ID of the post to edit.
  * @param {?Object} settings     Editor settings object.
  * @param {Object}  initialEdits Programmatic edits to apply initially, to be
@@ -170,3 +166,4 @@ export { default as PluginSidebar } from './components/sidebar/plugin-sidebar';
 export { default as PluginSidebarMoreMenuItem } from './components/header/plugin-sidebar-more-menu-item';
 export { default as __experimentalFullscreenModeClose } from './components/header/fullscreen-mode-close';
 export { default as __experimentalMainDashboardButton } from './components/header/main-dashboard-button';
+export { store } from './store';

packages/edit-post/src/store/actions.js

@@ -9,7 +9,7 @@ import { castArray, reduce } from 'lodash';
 import { __ } from '@wordpress/i18n';
 import { apiFetch } from '@wordpress/data-controls';
 import { store as interfaceStore } from '@wordpress/interface';
-import { controls, dispatch, select, subscribe } from '@wordpress/data';
+import { controls, select, subscribe, dispatch } from '@wordpress/data';
 import { speak } from '@wordpress/a11y';
 import { store as noticesStore } from '@wordpress/notices';
 import { store as coreStore } from '@wordpress/core-data';
@@ -265,8 +265,6 @@ export function showBlockTypes( blockNames ) {
 	};
 }
 
-let saveMetaboxUnsubscribe;
-
 /**
  * Returns an action object used in signaling
  * what Meta boxes are available in which location.
@@ -280,52 +278,6 @@ export function* setAvailableMetaBoxesPerLocation( metaBoxesPerLocation ) {
 		type: 'SET_META_BOXES_PER_LOCATIONS',
 		metaBoxesPerLocation,
 	};
-
-	const postType = yield controls.select( editorStore, 'getCurrentPostType' );
-	if ( window.postboxes.page !== postType ) {
-		window.postboxes.add_postbox_toggles( postType );
-	}
-
-	let wasSavingPost = yield controls.select( editorStore, 'isSavingPost' );
-	let wasAutosavingPost = yield controls.select(
-		editorStore,
-		'isAutosavingPost'
-	);
-
-	// Meta boxes are initialized once at page load. It is not necessary to
-	// account for updates on each state change.
-	//
-	// See: https://github.com/WordPress/WordPress/blob/5.1.1/wp-admin/includes/post.php#L2307-L2309
-	const hasActiveMetaBoxes = yield controls.select(
-		editPostStore,
-		'hasMetaBoxes'
-	);
-
-	// First remove any existing subscription in order to prevent multiple saves
-	if ( !! saveMetaboxUnsubscribe ) {
-		saveMetaboxUnsubscribe();
-	}
-
-	// Save metaboxes when performing a full save on the post.
-	saveMetaboxUnsubscribe = subscribe( () => {
-		const isSavingPost = select( editorStore ).isSavingPost();
-		const isAutosavingPost = select( editorStore ).isAutosavingPost();
-
-		// Save metaboxes on save completion, except for autosaves that are not a post preview.
-		const shouldTriggerMetaboxesSave =
-			hasActiveMetaBoxes &&
-			wasSavingPost &&
-			! isSavingPost &&
-			! wasAutosavingPost;
-
-		// Save current state for next inspection.
-		wasSavingPost = isSavingPost;
-		wasAutosavingPost = isAutosavingPost;
-
-		if ( shouldTriggerMetaboxesSave ) {
-			dispatch( editPostStore ).requestMetaBoxUpdates();
-		}
-	} );
 }
 
 /**
@@ -531,3 +483,69 @@ export function* __unstableCreateTemplate( template ) {
 		}
 	);
 }
+
+let metaBoxesInitialized = false;
+
+/**
+ * Initializes WordPress `postboxes` script and the logic for saving meta boxes.
+ */
+export function* initializeMetaBoxes() {
+	const isEditorReady = yield controls.select(
+		editorStore,
+		'__unstableIsEditorReady'
+	);
+
+	if ( ! isEditorReady ) {
+		return;
+	}
+
+	const postType = yield controls.select( editorStore, 'getCurrentPostType' );
+
+	// Only initialize once.
+	if ( metaBoxesInitialized ) {
+		return;
+	}
+
+	if ( window.postboxes.page !== postType ) {
+		window.postboxes.add_postbox_toggles( postType );
+	}
+
+	metaBoxesInitialized = true;
+
+	let wasSavingPost = yield controls.select( editorStore, 'isSavingPost' );
+	let wasAutosavingPost = yield controls.select(
+		editorStore,
+		'isAutosavingPost'
+	);
+	const hasMetaBoxes = yield controls.select( editPostStore, 'hasMetaBoxes' );
+
+	// Save metaboxes when performing a full save on the post.
+	subscribe( () => {
+		const isSavingPost = select( editorStore ).isSavingPost();
+		const isAutosavingPost = select( editorStore ).isAutosavingPost();
+
+		// Save metaboxes on save completion, except for autosaves that are not a post preview.
+		//
+		// Meta boxes are initialized once at page load. It is not necessary to
+		// account for updates on each state change.
+		//
+		// See: https://github.com/WordPress/WordPress/blob/5.1.1/wp-admin/includes/post.php#L2307-L2309
+		const shouldTriggerMetaboxesSave =
+			hasMetaBoxes &&
+			wasSavingPost &&
+			! isSavingPost &&
+			! wasAutosavingPost;
+
+		// Save current state for next inspection.
+		wasSavingPost = isSavingPost;
+		wasAutosavingPost = isAutosavingPost;
+
+		if ( shouldTriggerMetaboxesSave ) {
+			dispatch( editPostStore ).requestMetaBoxUpdates();
+		}
+	} );
+
+	return {
+		type: 'META_BOXES_INITIALIZED',
+	};
+}

packages/edit-post/src/store/reducer.js

@@ -281,9 +281,26 @@ function isEditingTemplate( state = false, action ) {
 	return state;
 }
 
+/**
+ * Reducer tracking whether meta boxes are initialized.
+ *
+ * @param {boolean} state
+ * @param {Object}  action
+ *
+ * @return {boolean} Updated state.
+ */
+function metaBoxesInitialized( state = false, action ) {
+	switch ( action.type ) {
+		case 'META_BOXES_INITIALIZED':
+			return true;
+	}
+	return state;
+}
+
 const metaBoxes = combineReducers( {
 	isSaving: isSavingMetaBoxes,
 	locations: metaBoxLocations,
+	initialized: metaBoxesInitialized,
 } );
 
 export default combineReducers( {

packages/edit-post/src/store/selectors.js

@@ -367,6 +367,17 @@ export function isEditingTemplate( state ) {
 	return state.isEditingTemplate;
 }
 
+/**
+ * Returns true if meta boxes are initialized.
+ *
+ * @param {Object} state Global application state.
+ *
+ * @return {boolean} Whether meta boxes are initialized.
+ */
+export function areMetaBoxesInitialized( state ) {
+	return state.metaBoxes.initialized;
+}
+
 /**
  * Retrieves the template of the currently edited post.
  *