Build: Add globalThis DefinePlugin config to webpack

This updates the build to account for related changes in WordPress packages. More details in WordPress/gutenberg#61486.

Props jonsurrell, youknowriad, swissspidy, gziolo.
Fixes #61262.




git-svn-id: https://develop.svn.wordpress.org/trunk@58193 602fd350-edb4-49c9-b593-d223f7449a82

tools/webpack/shared.js

@@ -41,12 +41,30 @@ const getBaseConfig = ( env ) => {
 		watch: env.watch,
 		plugins: [
 			new DefinePlugin( {
+				/*
+				 * These variables are part of https://github.com/WordPress/gutenberg/pull/61486
+				 * They're expected to be released in an upcoming version of Gutenberg.
+				 *
+				 * Defining this before the packages are released is harmless.
+				 *
+				 * @todo Remove the non-globalThis defines here when packages have been upgraded to the globalThis versions.
+				 */
+
+				// Inject the `IS_GUTENBERG_PLUGIN` global, used for feature flagging.
+				'globalThis.IS_GUTENBERG_PLUGIN': JSON.stringify( false ),
+				// Inject the `IS_WORDPRESS_CORE` global, used for feature flagging.
+				'globalThis.IS_WORDPRESS_CORE': JSON.stringify( true ),
+				// Inject the `SCRIPT_DEBUG` global, used for dev versions of JavaScript.
+				'globalThis.SCRIPT_DEBUG': JSON.stringify(
+					mode === 'development'
+				),
+
 				// Inject the `IS_GUTENBERG_PLUGIN` global, used for feature flagging.
-				'process.env.IS_GUTENBERG_PLUGIN': false,
+				'process.env.IS_GUTENBERG_PLUGIN': JSON.stringify( false ),
 				// Inject the `IS_WORDPRESS_CORE` global, used for feature flagging.
-				'process.env.IS_WORDPRESS_CORE': true,
+				'process.env.IS_WORDPRESS_CORE': JSON.stringify( true ),
 				// Inject the `SCRIPT_DEBUG` global, used for dev versions of JavaScript.
-				SCRIPT_DEBUG: mode === 'development',
+				SCRIPT_DEBUG: JSON.stringify( mode === 'development' ),
 			} ),
 		],
 	};