Core: Move the factory to separate exports

Since versions 1.11.0/2.1.0, jQuery has used a module wrapper with one strange
addition - in CommonJS environments, if a global `window` with a `document` was
not present, jQuery exported a factory accepting a `window` implementation and
returning jQuery.

This approach created a number of problems:
1. Properly typing jQuery would be a nightmare as the exported value depends on
   the environment. In practice, typing definitions ignored the factory case.
2. Since we now use named exports for the jQuery module version, it felt weird
   to have `jQuery` and `$` pointing to the factory instead of real jQuery.

Instead, for jQuery 4.0 we leverage the just added `exports` field in
`package.json` to expose completely separate factory entry points: one for the
full build, one for the slim one.

Exports definitions for `./factory` & `./factory-slim` are simpler than for `.`
and `./slim` - this is because it's a new entry point, we only expose a named
export and so there's no issue with just pointing Node.js to the CommonJS
version (we cannot use the module version for `import` from Node.js to avoid
double package hazard). The factory entry points are also not meant for the Web
browser which always has a proper `window` - and they'd be unfit for an
inclusion in a regular script tag anyway. Because of that, we also don't
generate minified versions of these entry points.

The factory files are not pushed to the CDN since they are mostly aimed
at Node.js.

Closes gh-5293

3 files changed, 167 insertions, 23 deletions

diff --git a/build/tasks/build.js b/build/tasks/build.js
index 1a0d7d75a..69a4de7c7 100644
--- a/build/tasks/build.js
+++ b/build/tasks/build.js
@@ -15,6 +15,7 @@ const excludedFromSlim = require( "./lib/slim-exclude" );
 const rollupFileOverrides = require( "./lib/rollup-plugin-file-overrides" );
 const pkg = require( "../../package.json" );
 const isCleanWorkingDir = require( "./lib/isCleanWorkingDir" );
+const processForDist = require( "./dist" );
 const minify = require( "./minify" );
 const getTimestamp = require( "./lib/getTimestamp" );
 const verifyNodeVersion = require( "./lib/verifyNodeVersion" );
@@ -71,8 +72,16 @@ async function readdirRecursive( dir, all = [] ) {
 	return all;
 }
 
-async function getOutputRollupOptions( { esm = false } = {} ) {
-	const wrapperFileName = `wrapper${esm ? "-esm" : ""}.js`;
+async function getOutputRollupOptions( {
+	esm = false,
+	factory = false
+} = {} ) {
+	const wrapperFileName = `wrapper${
+		factory ? "-factory" : ""
+	}${
+		esm ? "-esm" : ""
+	}.js`;
+
 	const wrapperSource = await read( wrapperFileName );
 
 	// Catch `// @CODE` and subsequent comment lines event if they don't start
@@ -163,6 +172,7 @@ async function build( {
 	filename = "jquery.js",
 	include = [],
 	esm = false,
+	factory = false,
 	slim = false,
 	version,
 	watch = false
@@ -275,7 +285,7 @@ async function build( {
 		plugins: [ rollupFileOverrides( fileOverrides ) ]
 	} );
 
-	const outputOptions = await getOutputRollupOptions( { esm } );
+	const outputOptions = await getOutputRollupOptions( { esm, factory } );
 
 	if ( watch ) {
 		const watcher = rollup.watch( {
@@ -305,7 +315,11 @@ async function build( {
 						version
 					} );
 
-					await minify( { dir, filename, esm } );
+					// Don't minify factory files; they are not meant
+					// for the browser anyway.
+					if ( !factory ) {
+						await minify( { dir, filename, esm } );
+					}
 					break;
 			}
 		} );
@@ -317,7 +331,22 @@ async function build( {
 		} = await bundle.generate( outputOptions );
 
 		await writeCompiled( { code, dir, filename, version } );
-		await minify( { dir, filename, esm } );
+
+		// Don't minify factory files; they are not meant
+		// for the browser anyway.
+		if ( !factory ) {
+			await minify( { dir, filename, esm } );
+		} else {
+
+			// We normally process for dist during minification to save
+			// file reads. However, some files are not minified and then
+			// we need to do it separately.
+			const contents = await fs.promises.readFile(
+				path.join( dir, filename ),
+				"utf8"
+			);
+			processForDist( contents, filename );
+		}
 	}
 }
 
@@ -339,6 +368,37 @@ async function buildDefaultFiles( { version, watch } = {} ) {
 			slim: true,
 			version,
 			watch
+		} ),
+
+		build( {
+			filename: "jquery.factory.js",
+			factory: true,
+			version,
+			watch
+		} ),
+		build( {
+			filename: "jquery.factory.slim.js",
+			slim: true,
+			factory: true,
+			version,
+			watch
+		} ),
+		build( {
+			dir: "dist-module",
+			filename: "jquery.factory.module.js",
+			esm: true,
+			factory: true,
+			version,
+			watch
+		} ),
+		build( {
+			dir: "dist-module",
+			filename: "jquery.factory.slim.module.js",
+			esm: true,
+			slim: true,
+			factory: true,
+			version,
+			watch
 		} )
 	] );
 
diff --git a/build/tasks/dist.js b/build/tasks/dist.js
index d6488aa1b..f15689e3d 100644
--- a/build/tasks/dist.js
+++ b/build/tasks/dist.js
@@ -1,7 +1,7 @@
 "use strict";
 
 // Process files for distribution.
-module.exports = async function processForDist( text, filename ) {
+module.exports = function processForDist( text, filename ) {
 	if ( !text ) {
 		throw new Error( "text required for processForDist" );
 	}
diff --git a/build/tasks/node_smoke_tests.js b/build/tasks/node_smoke_tests.js
index 5aa7660b0..433a005d5 100644
--- a/build/tasks/node_smoke_tests.js
+++ b/build/tasks/node_smoke_tests.js
@@ -5,7 +5,8 @@ const util = require( "util" );
 const exec = util.promisify( require( "child_process" ).exec );
 const verifyNodeVersion = require( "./lib/verifyNodeVersion" );
 
-const allowedModules = [ "commonjs", "module" ];
+const allowedLibraryTypes = [ "regular", "factory" ];
+const allowedSourceTypes = [ "commonjs", "module" ];
 
 if ( !verifyNodeVersion() ) {
 	return;
@@ -17,33 +18,116 @@ if ( !verifyNodeVersion() ) {
 // important so that the tests & the main process don't interfere with
 // each other, e.g. so that they don't share the `require` cache.
 
-async function runTests( sourceType, module ) {
-	if ( !allowedModules.includes( sourceType ) ) {
-		throw new Error(
-			`Usage: \`node_smoke_tests [${allowedModules.join( "|" )}]:JQUERY\``
-		);
+async function runTests( { libraryType, sourceType, module } ) {
+	if ( !allowedLibraryTypes.includes( libraryType ) ||
+			!allowedSourceTypes.includes( sourceType ) ) {
+		throw new Error( `Incorrect libraryType or sourceType value; passed: ${
+			libraryType
+		} ${ sourceType } "${ module }"` );
 	}
-	const dir = `./test/node_smoke_tests/${sourceType}`;
+	const dir = `./test/node_smoke_tests/${ sourceType }/${ libraryType }`;
 	const files = await fs.promises.readdir( dir, { withFileTypes: true } );
 	const testFiles = files.filter( ( testFilePath ) => testFilePath.isFile() );
+
+	if ( !testFiles.length ) {
+		throw new Error( `No test files found for ${
+			libraryType
+		} ${ sourceType } "${ module }"` );
+	}
+
 	await Promise.all(
 		testFiles.map( ( testFile ) =>
-			exec( `node "${dir}/${testFile.name}" "${module}"` )
+			exec( `node "${ dir }/${ testFile.name }" "${ module }"` )
 		)
 	);
-	console.log( `Node smoke tests passed for ${sourceType} "${module}".` );
+	console.log( `Node smoke tests passed for ${
+		libraryType
+	} ${ sourceType } "${ module }".` );
 }
 
 async function runDefaultTests() {
 	await Promise.all( [
-		runTests( "commonjs", "jquery" ),
-		runTests( "commonjs", "jquery/slim" ),
-		runTests( "commonjs", "./dist/jquery.js" ),
-		runTests( "commonjs", "./dist/jquery.slim.js" ),
-		runTests( "module", "jquery" ),
-		runTests( "module", "jquery/slim" ),
-		runTests( "module", "./dist-module/jquery.module.js" ),
-		runTests( "module", "./dist-module/jquery.slim.module.js" )
+		runTests( {
+			libraryType: "regular",
+			sourceType: "commonjs",
+			module: "jquery"
+		} ),
+		runTests( {
+			libraryType: "regular",
+			sourceType: "commonjs",
+			module: "jquery/slim"
+		} ),
+		runTests( {
+			libraryType: "regular",
+			sourceType: "commonjs",
+			module: "./dist/jquery.js"
+		} ),
+		runTests( {
+			libraryType: "regular",
+			sourceType: "commonjs",
+			module: "./dist/jquery.slim.js"
+		} ),
+		runTests( {
+			libraryType: "regular",
+			sourceType: "module",
+			module: "jquery"
+		} ),
+		runTests( {
+			libraryType: "regular",
+			sourceType: "module",
+			module: "jquery/slim"
+		} ),
+		runTests( {
+			libraryType: "regular",
+			sourceType: "module",
+			module: "./dist-module/jquery.module.js"
+		} ),
+		runTests( {
+			libraryType: "regular",
+			sourceType: "module",
+			module: "./dist-module/jquery.slim.module.js"
+		} ),
+
+		runTests( {
+			libraryType: "factory",
+			sourceType: "commonjs",
+			module: "jquery/factory"
+		} ),
+		runTests( {
+			libraryType: "factory",
+			sourceType: "commonjs",
+			module: "jquery/factory-slim"
+		} ),
+		runTests( {
+			libraryType: "factory",
+			sourceType: "commonjs",
+			module: "./dist/jquery.factory.js"
+		} ),
+		runTests( {
+			libraryType: "factory",
+			sourceType: "commonjs",
+			module: "./dist/jquery.factory.slim.js"
+		} ),
+		runTests( {
+			libraryType: "factory",
+			sourceType: "module",
+			module: "jquery/factory"
+		} ),
+		runTests( {
+			libraryType: "factory",
+			sourceType: "module",
+			module: "jquery/factory-slim"
+		} ),
+		runTests( {
+			libraryType: "factory",
+			sourceType: "module",
+			module: "./dist-module/jquery.factory.module.js"
+		} ),
+		runTests( {
+			libraryType: "factory",
+			sourceType: "module",
+			module: "./dist-module/jquery.factory.slim.module.js"
+		} )
 	] );
 }