use assign helper, to avoid compatibility headaches

src/generators/dom/index.js

@@ -241,7 +241,7 @@ export default function dom ( parsed, source, options ) {
 	}
 
 	builders._set.addLine( 'var oldState = this._state;' );
-	builders._set.addLine( 'this._state = Object.assign( {}, oldState, newState );' );
+	builders._set.addLine( `this._state = ${generator.helper( 'assign' )}( {}, oldState, newState );` );
 
 	if ( computations.length ) {
 		const builder = new CodeBuilder();
@@ -340,7 +340,7 @@ export default function dom ( parsed, source, options ) {
 	if ( generator.usesRefs ) constructorBlock.addLine( `this.refs = {};` );
 
 	constructorBlock.addLine(
-		`this._state = ${templateProperties.data ? `Object.assign( ${generator.alias( 'template' )}.data(), options.data )` : `options.data || {}`};`
+		`this._state = ${templateProperties.data ? `${generator.helper( 'assign' )}( ${generator.alias( 'template' )}.data(), options.data )` : `options.data || {}`};`
 	);
 
 	if ( !generator.builders.metaBindings.isEmpty() ) {
@@ -393,7 +393,7 @@ export default function dom ( parsed, source, options ) {
 
 	if ( sharedPath ) {
 		const base = templateProperties.methods ? `{}, ${generator.alias( 'template' )}.methods` : `{}`;
-		builders.main.addBlock( `${name}.prototype = Object.assign( ${base}, ${generator.helper( 'proto' )} );` );
+		builders.main.addBlock( `${name}.prototype = ${generator.helper( 'assign' )}( ${base}, ${generator.helper( 'proto' )} );` );
 	} else {
 		if ( templateProperties.methods ) {
 			builders.main.addBlock( `${name}.prototype = ${generator.alias( 'template' )}.methods;` );

src/shared/index.js

@@ -3,6 +3,15 @@ export * from './methods.js';
 
 export function noop () {}
 
+export function assign ( target ) {
+	for ( var i = 1; i < arguments.length; i += 1 ) {
+		var source = arguments[i];
+		for ( var k in source ) target[k] = source[k];
+	}
+
+	return target;
+}
+
 export function differs ( a, b ) {
 	return ( a !== b ) || ( a && ( typeof a === 'object' ) || ( typeof a === 'function' ) );
 }

test/generator/index.js

@@ -30,6 +30,8 @@ require.extensions[ '.html' ] = function ( module, filename ) {
 	return module._compile( code, filename );
 };
 
+const Object_assign = Object.assign;
+
 describe( 'generate', () => {
 	before( setupHtmlEqual );
 
@@ -93,6 +95,10 @@ describe( 'generate', () => {
 
 			return env()
 				.then( window => {
+					Object.assign = () => {
+						throw new Error( 'cannot use Object.assign in generated code, as it is not supported everywhere' );
+					};
+
 					global.window = window;
 
 					// Put the constructor on window for testing
@@ -145,6 +151,9 @@ describe( 'generate', () => {
 						if ( !config.show ) console.log( addLineNumbers( code ) ); // eslint-disable-line no-console
 						throw err;
 					}
+				})
+				.then( () => {
+					Object.assign = Object_assign;
 				});
 		});
 	}