Core: Migrate from AMD to ES modules 🎉

Migrate all source AMD modules to ECMAScript modules. The final bundle
is compiled by a custom build process that uses Rollup under the hood.

Test files themselves are still loaded via RequireJS as that has to work in
IE 11.

Tests can now be run in "Load as modules" mode which replaces the previous
"Load with AMD" option. That option of running tests doesn't work in IE
and Edge as it requires support for dynamic imports.

Some of the changes required by the migration:
* check `typeof` of `noGlobal` instead of using the variable directly
  as it's not available when modules are used
* change the nonce module to be an object as ECMASscript module exports
  are immutable
* remove some unused exports
* import `./core/parseHTML.js` directly in `jquery.js` so that it's not
  being cut out when the `ajax` module is excluded in a custom compilation

Closes gh-4541

1 files changed, 21 insertions, 16 deletions

diff --git a/test/jquery.js b/test/jquery.js
index 6b1aef42f..d6d53fb26 100644
--- a/test/jquery.js
+++ b/test/jquery.js
@@ -2,7 +2,8 @@
 ( function() {
 	/* global loadTests: false */
 
-	var FILEPATH = "/test/jquery.js",
+	var dynamicImportSource,
+		FILEPATH = "/test/jquery.js",
 		activeScript = [].slice.call( document.getElementsByTagName( "script" ), -1 )[ 0 ],
 		parentUrl = activeScript && activeScript.src ?
 			activeScript.src.replace( /[?#].*/, "" ) + FILEPATH.replace( /[^/]+/g, ".." ) + "/" :
@@ -21,12 +22,13 @@
 	// Define configuration parameters controlling how jQuery is loaded
 	if ( QUnit ) {
 
-		// AMD loading is asynchronous and incompatible with synchronous test loading in Karma
+		// ES modules loading is asynchronous and incompatible with synchronous
+		// test loading in Karma.
 		if ( !window.__karma__ ) {
 			QUnit.config.urlConfig.push( {
-				id: "amd",
-				label: "Load with AMD",
-				tooltip: "Load the AMD jQuery file (and its dependencies)"
+				id: "esmodules",
+				label: "Load as modules",
+				tooltip: "Load a relevant jQuery module file (and its dependencies)"
 			} );
 		}
 
@@ -39,18 +41,21 @@
 
 	// Honor AMD loading on the main window (detected by seeing QUnit on it).
 	// This doesn't apply to iframes because they synchronously expect jQuery to be there.
-	if ( urlParams.amd && window.QUnit ) {
-		require.config( {
-			baseUrl: parentUrl
-		} );
-		src = "src/jquery";
+	if ( urlParams.esmodules && window.QUnit ) {
 
-		// Include tests if specified
-		if ( typeof loadTests !== "undefined" ) {
-			require( [ src ], loadTests );
-		} else {
-			require( [ src ] );
-		}
+		// Support: IE 11+, Edge 12 - 18+
+		// IE/Edge don't support the dynamic import syntax so they'd crash
+		// with a SyntaxError here.
+		dynamicImportSource = "" +
+			"import( `${ parentUrl }src/jquery.js` ).then( ( { default: jQuery } ) => {\n" +
+			"	window.jQuery = jQuery;\n" +
+			"	if ( typeof loadTests === \"function\" ) {\n" +
+			"		// Include tests if specified\n" +
+			"		loadTests();\n" +
+			"	}\n" +
+			"} );";
+
+		eval( dynamicImportSource );
 
 	// Otherwise, load synchronously
 	} else {