Data Module: Expose state using selectors

data/README.md

@@ -22,4 +22,43 @@ Registers a [`listener`](https://redux.js.org/docs/api/Store.html#subscribe) fun
 
 #### `store.dispatch( action: object )`
 
-The dispatch function should be called to trigger the registered reducers function and update the state. An [`action`](https://redux.js.org/docs/api/Store.html#dispatch)object should be passed to this action. This action is passed to the registered reducers in addition to the previous state.
+The dispatch function should be called to trigger the registered reducers function and update the state. An [`action`](https://redux.js.org/docs/api/Store.html#dispatch) object should be passed to this function. This action is passed to the registered reducers in addition to the previous state.
+
+
+### `wp.data.registerSelectors( reducerKey: string, newSelectors: object )`
+
+If your module or plugin needs to expose its state to other modules and plugins, you'll have to register state selectors.
+
+A selector is a function that takes the current state value as a first argument and extra arguments if needed and returns any data extracted from the state.
+
+#### Example:
+
+Let's say the state of our plugin (registered with the key `myPlugin`) has the following shape: `{ title: 'My post title' }`. We can register a `getTitle` selector to make this state value available like so:
+
+```js
+wp.data.registerSelectors( 'myPlugin', { getTitle: ( state ) => state.title } );
+```
+
+### `wp.data.select( key: string, selectorName: string, ...args )`
+
+This function allows calling any registered selector. Given a module's key, a selector's name and extra arguments passed to the selector, this function calls the selector passing it the current state and the extra arguments provided.
+
+#### Example:
+
+```js
+wp.data.select( 'myPlugin', 'getTitle' ); // Returns "My post title"
+```
+
+### `wp.data.query( mapSelectorsToProps: func )( WrappedComponent: Component )`
+
+If you use a React or WordPress Element, a Higher Order Component is made available to inject data into your components like so:
+
+```js
+const Component = ( { title } ) => <div>{ title }</div>;
+
+wp.data.query( select => {
+	return {
+		title: select( 'myPlugin', 'getTitle' ),
+	};
+} )( Component );
+```

data/index.js

@@ -1,13 +1,15 @@
 /**
  * External dependencies
  */
+import { connect } from 'react-redux';
 import { createStore, combineReducers } from 'redux';
 import { flowRight } from 'lodash';
 
 /**
  * Module constants
  */
 const reducers = {};
+const selectors = {};
 const enhancers = [];
 if ( window.__REDUX_DEVTOOLS_EXTENSION__ ) {
 	enhancers.push( window.__REDUX_DEVTOOLS_EXTENSION__() );
@@ -17,17 +19,17 @@ const initialReducer = () => ( {} );
 const store = createStore( initialReducer, {}, flowRight( enhancers ) );
 
 /**
- * Registers a new sub reducer to the global state and returns a Redux-like store object.
+ * Registers a new sub-reducer to the global state and returns a Redux-like store object.
  *
- * @param {String}  key     Reducer key
- * @param {Object}  reducer Reducer function
+ * @param {string}  reducerKey Reducer key.
+ * @param {Object}  reducer    Reducer function.
  *
- * @returns {Object} Store Object.
+ * @returns {Object}           Store Object.
  */
-export function registerReducer( key, reducer ) {
-	reducers[ key ] = reducer;
+export function registerReducer( reducerKey, reducer ) {
+	reducers[ reducerKey ] = reducer;
 	store.replaceReducer( combineReducers( reducers ) );
-	const getState = () => store.getState()[ key ];
+	const getState = () => store.getState()[ reducerKey ];
 
 	return {
 		dispatch: store.dispatch,
@@ -46,3 +48,55 @@ export function registerReducer( key, reducer ) {
 		getState,
 	};
 }
+
+/**
+ * Registers selectors for external usage.
+ *
+ * @param {string} reducerKey          Part of the state shape to register the
+ *                                     selectors for.
+ * @param {Object} newSelectors        Selectors to register. Keys will be used
+ *                                     as the public facing API. Selectors will
+ *                                     get passed the state as first argument.
+ */
+export function registerSelectors( reducerKey, newSelectors ) {
+	selectors[ reducerKey ] = newSelectors;
+}
+
+/**
+ * Higher Order Component used to inject data using the registered selectors.
+ *
+ * @param {Function} mapSelectorsToProps Gets called with the selectors object
+ *                                       to determine the data for the component.
+ *
+ * @returns {Func}                       Renders the wrapped component and passes it data.
+ */
+export const query = ( mapSelectorsToProps ) => ( WrappedComponent ) => {
+	const connectWithStore = ( ...args ) => {
+		const ConnectedWrappedComponent = connect( ...args )( WrappedComponent );
+		return ( props ) => {
+			return <ConnectedWrappedComponent { ...props } store={ store } />;
+		};
+	};
+
+	return connectWithStore( ( state, ownProps ) => {
+		const select = ( key, selectorName, ...args ) => {
+			return selectors[ key ][ selectorName ]( state[ key ], ...args );
+		};
+
+		return mapSelectorsToProps( select, ownProps );
+	} );
+};
+
+/**
+ * Calls a selector given the current state and extra arguments.
+ *
+ * @param {string} reducerKey   Part of the state shape to register the
+ *                              selectors for.
+ * @param {string} selectorName Selector name.
+ * @param {*}      args         Selectors arguments.
+ *
+ * @returns {*}                 The selector's returned value.
+ */
+export const select = ( reducerKey, selectorName, ...args ) => {
+	return selectors[ reducerKey ][ selectorName ]( store.getState()[ reducerKey ], ...args );
+};

data/test/__snapshots__/index.js.snap

@@ -0,0 +1,7 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`query passes the relevant data to the component 1`] = `
+<div>
+  reactState
+</div>
+`;

data/test/index.js

@@ -1,4 +1,12 @@
-import { registerReducer } from '../';
+/**
+ * External dependencies
+ */
+import { render } from 'enzyme';
+
+/**
+ * Internal dependencies
+ */
+import { registerReducer, registerSelectors, select, query } from '../';
 
 describe( 'store', () => {
 	it( 'Should append reducers to the state', () => {
@@ -12,3 +20,42 @@ describe( 'store', () => {
 		expect( store2.getState() ).toEqual( 'ribs' );
 	} );
 } );
+
+describe( 'select', () => {
+	it( 'registers multiple selectors to the public API', () => {
+		const store = registerReducer( 'reducer1', () => 'state1' );
+		const selector1 = jest.fn( () => 'result1' );
+		const selector2 = jest.fn( () => 'result2' );
+
+		registerSelectors( 'reducer1', {
+			selector1,
+			selector2,
+		} );
+
+		expect( select( 'reducer1', 'selector1' ) ).toEqual( 'result1' );
+		expect( selector1 ).toBeCalledWith( store.getState() );
+
+		expect( select( 'reducer1', 'selector2' ) ).toEqual( 'result2' );
+		expect( selector2 ).toBeCalledWith( store.getState() );
+	} );
+} );
+
+describe( 'query', () => {
+	it( 'passes the relevant data to the component', () => {
+		registerReducer( 'reactReducer', () => ( { reactKey: 'reactState' } ) );
+		registerSelectors( 'reactReducer', {
+			reactSelector: ( state, key ) => state[ key ],
+		} );
+		const Component = query( ( selectFunc, ownProps ) => {
+			return {
+				data: selectFunc( 'reactReducer', 'reactSelector', ownProps.keyName ),
+			};
+		} )( ( props ) => {
+			return <div>{ props.data }</div>;
+		} );
+
+		const tree = render( <Component keyName="reactKey" /> );
+
+		expect( tree ).toMatchSnapshot();
+	} );
+} );

editor/store/index.js

@@ -1,7 +1,7 @@
 /**
  * WordPress Dependencies
  */
-import { registerReducer } from '@wordpress/data';
+import { registerReducer, registerSelectors } from '@wordpress/data';
 
 /**
  * Internal dependencies
@@ -12,16 +12,20 @@ import { withRehydratation, loadAndPersist } from './persist';
 import enhanceWithBrowserSize from './mobile';
 import applyMiddlewares from './middlewares';
 import { BREAK_MEDIUM } from './constants';
+import { getEditedPostTitle } from './selectors';
 
 /**
  * Module Constants
  */
 const STORAGE_KEY = `GUTENBERG_PREFERENCES_${ window.userSettings.uid }`;
+const MODULE_KEY = 'core/editor';
 
 const store = applyMiddlewares(
 	registerReducer( 'core/editor', withRehydratation( reducer, 'preferences' ) )
 );
 loadAndPersist( store, 'preferences', STORAGE_KEY, PREFERENCES_DEFAULTS );
 enhanceWithBrowserSize( store, BREAK_MEDIUM );
 
+registerSelectors( MODULE_KEY, { getEditedPostTitle } );
+
 export default store;

lib/client-assets.php

@@ -79,7 +79,7 @@ function gutenberg_register_scripts_and_styles() {
 	wp_register_script(
 		'wp-data',
 		gutenberg_url( 'data/build/index.js' ),
-		array(),
+		array( 'wp-element' ),
 		filemtime( gutenberg_dir_path() . 'data/build/index.js' )
 	);
 	wp_register_script(