Error checking in select API

data/index.js

@@ -3,7 +3,7 @@
  */
 import { connect } from 'react-redux';
 import { createStore } from 'redux';
-import { flowRight, without, mapValues } from 'lodash';
+import { flowRight, without, mapValues, get } from 'lodash';
 
 /**
  * Internal dependencies
@@ -100,10 +100,6 @@ export const query = ( mapSelectorsToProps ) => ( WrappedComponent ) => {
 	};
 
 	return connectWithStore( ( state, ownProps ) => {
-		const select = ( key, selectorName, ...args ) => {
-			return selectors[ key ][ selectorName ]( state[ key ], ...args );
-		};
-
 		return mapSelectorsToProps( select, ownProps );
 	} );
 };
@@ -119,5 +115,12 @@ export const query = ( mapSelectorsToProps ) => ( WrappedComponent ) => {
  * @return {*} The selector's returned value.
  */
 export const select = ( reducerKey, selectorName, ...args ) => {
+	const selector = get( selectors, [ reducerKey, selectorName ] );
+	if ( typeof selector !== 'function' ) {
+		// eslint-disable-next-line no-console
+		console.error( `Invalid selector called, with name "${ selectorName }" for reducer "${ reducerKey }".` +
+			' Make sure the reducerName and selectorName are correct!' );
+		return undefined;
+	}
 	return selectors[ reducerKey ][ selectorName ]( stores[ reducerKey ].getState(), ...args );
 };

data/test/index.js

@@ -6,7 +6,24 @@ import { render } from 'enzyme';
 /**
  * Internal dependencies
  */
-import { registerReducer, registerSelectors, select, query, subscribe } from '../';
+let registerReducer, registerSelectors, select, query, subscribe;
+
+const loadModule = () => {
+	const module = require( '../' );
+	registerReducer = module.registerReducer;
+	registerSelectors = module.registerSelectors;
+	select = module.select;
+	query = module.query;
+	subscribe = module.subscribe;
+};
+
+/**
+ * Make sure every test is ran with a fresh data/index.js module.
+ */
+beforeEach( () => {
+	jest.resetModules();
+	loadModule();
+} );
 
 describe( 'store', () => {
 	it( 'Should append reducers to the state', () => {
@@ -38,6 +55,25 @@ describe( 'select', () => {
 		expect( select( 'reducer1', 'selector2' ) ).toEqual( 'result2' );
 		expect( selector2 ).toBeCalledWith( store.getState() );
 	} );
+
+	it( 'prints an error when a selector is called on a non-existing reducer', () => {
+		/* eslint-disable no-console */
+		expect( select( 'reducer1', 'selector1' ) ).toBeUndefined();
+		expect( console ).toHaveErroredWith( 'Invalid selector called, with name "selector1" for reducer "reducer1".' +
+			' Make sure the reducerName and selectorName are correct!' );
+		/* eslint-enable no-console */
+	} );
+
+	it( 'prints an error when a non-existing selector is called', () => {
+		/* eslint-disable no-console */
+		// Call register reducer to make sure the store is created.
+		registerReducer( 'reducer2', () => 'state1' );
+
+		expect( select( 'reducer2', 'selector2' ) ).toBeUndefined();
+		expect( console ).toHaveErroredWith( 'Invalid selector called, with name "selector2" for reducer "reducer2".' +
+			' Make sure the reducerName and selectorName are correct!' );
+		/* eslint-enable no-console */
+	} );
 } );
 
 describe( 'query', () => {