Add lodash as a vendor dependency

The @wordpress/wp-url package now requires lodash as a dependency. The lodash package is not available in WP 4.9 so we will have to register it ourselves.

includes/amp-helper-functions.php

@@ -421,6 +421,20 @@ function amp_register_default_scripts( $wp_scripts ) {
 		}
 	}
 
+	$vendor_scripts = [
+		'lodash' => [
+			'dependencies' => [],
+			'version'      => '4.17.15',
+		],
+	];
+	foreach ( $vendor_scripts as $handle => $handle_data ) {
+		if ( ! isset( $wp_scripts->registered[ $handle ] ) ) {
+			$path = amp_get_asset_url( sprintf( 'js/vendor/%s.js', $handle ) );
+
+			$wp_scripts->add( $handle, $path, $handle_data['dependencies'], $handle_data['version'], 1 );
+		}
+	}
+
 	// AMP Runtime.
 	$handle = 'amp-runtime';
 	$wp_scripts->add(

package.json

@@ -51,6 +51,7 @@
     "babel-plugin-inline-react-svg": "1.1.1",
     "babel-plugin-transform-react-remove-prop-types": "0.4.24",
     "browserslist": "4.10.0",
+    "copy-webpack-plugin": "5.1.1",
     "core-js": "3.6.4",
     "cross-env": "7.0.2",
     "css-loader": "3.4.2",

webpack.config.js

@@ -2,6 +2,7 @@
  * External dependencies
  */
 const path = require( 'path' );
+const CopyWebpackPlugin = require( 'copy-webpack-plugin' );
 const MiniCssExtractPlugin = require( 'mini-css-extract-plugin' );
 const OptimizeCSSAssetsPlugin = require( 'optimize-css-assets-webpack-plugin' );
 const RtlCssPlugin = require( 'rtlcss-webpack-plugin' );
@@ -198,6 +199,12 @@ const wpPolyfills = {
 				}
 			},
 		} ),
+		new CopyWebpackPlugin( [
+			{
+				from: 'node_modules/lodash/lodash.js',
+				to: './vendor/lodash.js',
+			},
+		] ),
 		new WebpackBar( {
 			name: 'WordPress Polyfills',
 			color: '#21a0d0',