Build: Auto-convert sources to AMD

jQuery source has been migrated in gh-4541 from AMD to ES modules. To maintain
support for consumers of our AMD modules, this commits adds a task transpiling
the ES modules sources in `src/` to AMD in `amd/`.

A "Load with AMD" checkbox was also restored to the QUnit setup. Note that,
contrary to jQuery 3.x, AMD files need to be generated via `grunt amd` or
`grunt` as sources are not authored in ECMAScript modules. To achieve a similar
no-compile experience during jQuery 4.x testing, use the new "Load as modules"
checkbox which works in all supported browsers except for IE & Edge (the
legacy, EdgeHTML-based one).

Ref gh-4541
Closes gh-4554

3 files changed, 30 insertions, 9 deletions

diff --git a/test/data/testinit.js b/test/data/testinit.js
index 7a8697189..4088e4671 100644
--- a/test/data/testinit.js
+++ b/test/data/testinit.js
@@ -299,14 +299,16 @@ QUnit.testUnlessIE = QUnit.isIE ? QUnit.skip : QUnit.test;
 
 this.loadTests = function() {
 
-	// Directly load tests that need synchronous evaluation
-	if ( !QUnit.urlParams.esmodules || document.readyState === "loading" ) {
+	// QUnit.config is populated from QUnit.urlParams but only at the beginning
+	// of the test run. We need to read both.
+	var amd = QUnit.config.amd || QUnit.urlParams.amd;
+
+	// Directly load tests that need evaluation before DOMContentLoaded.
+	if ( !amd || document.readyState === "loading" ) {
 		document.write( "<script src='" + parentUrl + "test/unit/ready.js'><\x2Fscript>" );
 	} else {
 		QUnit.module( "ready", function() {
-			QUnit.test( "jQuery ready", function( assert ) {
-				assert.ok( false, "Test should be initialized before DOM ready" );
-			} );
+			QUnit.skip( "jQuery ready tests skipped in async mode", function() {} );
 		} );
 	}
 
diff --git a/test/index.html b/test/index.html
index 632275bb3..fff50faab 100644
--- a/test/index.html
+++ b/test/index.html
@@ -19,7 +19,7 @@
 	<!-- See testinit for the list of tests -->
 	<script src="data/testinit.js"></script>
 
-	<!-- A script that includes jQuery min, dev, or ES modules -->
+	<!-- A script that includes jQuery min, dev, ES modules or AMD -->
 	<!-- Adds "basic" URL option, even to iframes -->
 	<!-- iframes will not load AMD as loading needs to be synchronous for some tests -->
 	<!-- Also executes the function above to load tests -->
@@ -29,7 +29,7 @@
 		// Load tests if they have not been loaded
 		// This is in a different script tag to ensure that
 		// jQuery is on the page when the testrunner executes
-		if ( !QUnit.urlParams.esmodules ) {
+		if ( !QUnit.urlParams.esmodules && !QUnit.urlParams.amd ) {
 			loadTests();
 		}
 	</script>
diff --git a/test/jquery.js b/test/jquery.js
index d6d53fb26..c34c7c491 100644
--- a/test/jquery.js
+++ b/test/jquery.js
@@ -28,7 +28,12 @@
 			QUnit.config.urlConfig.push( {
 				id: "esmodules",
 				label: "Load as modules",
-				tooltip: "Load a relevant jQuery module file (and its dependencies)"
+				tooltip: "Load the jQuery module file (and its dependencies)"
+			} );
+			QUnit.config.urlConfig.push( {
+				id: "amd",
+				label: "Load with AMD",
+				tooltip: "Load the AMD jQuery file (and its dependencies)"
 			} );
 		}
 
@@ -39,7 +44,7 @@
 		} );
 	}
 
-	// Honor AMD loading on the main window (detected by seeing QUnit on it).
+	// Honor ES modules 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.esmodules && window.QUnit ) {
 
@@ -57,6 +62,20 @@
 
 		eval( dynamicImportSource );
 
+	// Apply similar treatment for AMD modules
+	} else if ( urlParams.amd && window.QUnit ) {
+		require.config( {
+			baseUrl: parentUrl
+		} );
+		src = "amd/jquery";
+
+		// Include tests if specified
+		if ( typeof loadTests !== "undefined" ) {
+			require( [ src ], loadTests );
+		} else {
+			require( [ src ] );
+		}
+
 	// Otherwise, load synchronously
 	} else {
 		document.write( "<script id='jquery-js' nonce='jquery+hardcoded+nonce' src='" + parentUrl + src + "'><\x2Fscript>" );