Build: Switch from UglifyJS to SWC minify, make the minified file ES5

More recent UglifyJS versions have started converting regular functions to arrow
ones, making ES5 source file migrated to a ES2015+ minified one. We want to
avoid that even in 1.14.x as long as we keep the source file in ES5.

Closes gh-2335
Ref mishoo/UglifyJS#5967
Ref jquery/download.jqueryui.com#629

1 files changed, 53 insertions, 0 deletions

diff --git a/build/tasks/minify.js b/build/tasks/minify.js
new file mode 100644
index 000000000..6d83831ee
--- /dev/null
+++ b/build/tasks/minify.js
@@ -0,0 +1,53 @@
+"use strict";
+
+const swc = require( "@swc/core" );
+
+module.exports = function( grunt ) {
+
+grunt.registerMultiTask( "minify", async function() {
+	const done = this.async();
+	const options = this.options();
+
+	for ( const file of this.files ) {
+		if ( file.src.length === 0 ) {
+			grunt.log.writeln(
+				`No source file found, skipping minification to "${ file.dest }".` );
+			continue;
+		}
+		if ( file.src.length !== 1 ) {
+			grunt.fail.warn( "Minifying multiple source files into one " +
+				"destination file not supported" );
+		}
+
+		const contents = grunt.file.read( file.src[ 0 ] );
+
+		const { code } = await swc.minify(
+			contents,
+			{
+				compress: {
+					ecma: 5,
+					hoist_funs: false,
+					loops: false
+				},
+				format: {
+					ecma: 5,
+					asciiOnly: true,
+					comments: false,
+					preamble: options.banner
+				},
+				inlineSourcesContent: false,
+				mangle: true,
+				module: false,
+				sourceMap: false
+			}
+		);
+
+		grunt.file.write( file.dest, code );
+
+		grunt.log.writeln( `File ${ file.dest } created.` );
+	}
+
+	done();
+} );
+
+};