Named register extra (#1855)

* named register extra

* use bundle: scheme

* document named register extra

* correct resolution adjustment

README.md

@@ -40,6 +40,7 @@ The following [pluggable extras](dist/extras) are provided which can be dropped
 * [AMD loading](dist/extras/amd.js) support (through `Window.define` which is created).
 * [Global loading](dist/extras/global.js) support for loading global scripts and detecting the defined global as the default export. Useful for loading common library scripts from CDN like `System.import('//unpkg.com/lodash')`. _(Already included in the system.js loader build)_.
 * [Named exports](dist/extras/named-exports.js) convenience extension support for global and AMD module formats (`import { x } from './global.js'` instead of `import G from './global.js'; G.x`)
+* [Named register](dist/extras/named-register.js) supports `System.register('name', ...)` named bundles (deprecated in the main build), that can be imported through a `bundle:` scheme, `System.import('bundle:name')`
 * [Transform loader](dist/extras/transform.js) support, using fetch and eval, supporting a hookable `loader.transform`
 
 Since all loader features are hookable, custom extensions can be easily made following the same approach as the bundled extras. See the [hooks documentation](docs/hooks.md) for more information.

src/common.js

@@ -42,7 +42,7 @@ export function resolveIfNotPlainOrUrl (relUrl, parentUrl) {
     }
     else {
       // resolving to :/ so pathname is the /... part
-      pathname = parentUrl.slice(parentProtocol.length + 1);
+      pathname = parentUrl.slice(parentProtocol.length + (parentUrl[parentProtocol.length] === '/'));
     }
 
     if (relUrl[0] === '/')

src/extras/named-register.js

@@ -0,0 +1,25 @@
+/*
+ * SystemJS named register extension
+ * Supports System.register('name', [..deps..], function (_export, _context) { ... })
+ * 
+ * Names are resolved origin-relative, so
+ * System.register(['x']) must be imported as System.import('/x')
+ */
+(function () {
+  const systemJSPrototype = System.constructor.prototype;
+
+  const registerRegistry = Object.create(null);
+
+  const register = systemJSPrototype.register;
+  systemJSPrototype.register = function (name, deps, declare) {
+    if (typeof name !== 'string')
+      return register.apply(this, arguments);
+    
+    registerRegistry['bundle:' + name] = [deps, declare];
+  };
+
+  const instantiate = systemJSPrototype.instantiate;
+  systemJSPrototype.instantiate = function (url, firstParentUrl) {
+    return registerRegistry[url] || instantiate.call(this, url, firstParentUrl);
+  };
+})();

test/browser/named-register.js

@@ -0,0 +1,11 @@
+suite('Named System.register', function() {
+  test('Loading a named System.register bundle', function () {
+    return System.import('./fixtures/browser/named-bundle.js').then(function (m) {
+      assert.equal(Object.keys(m).length, 0);
+      return System.import('bundle:a');
+    })
+    .then(function (m) {
+      assert.equal(m.a, 'b');
+    });
+  });
+});

test/fixtures/browser/named-bundle.js

@@ -0,0 +1,23 @@
+System.register('a', ['./b'], function (exports) {
+  var b;
+  return {
+    setters: [function (m) {
+      b = m.b;
+    }],
+    execute: function () {
+      exports({
+        a: b
+      });
+    }
+  };
+});
+
+System.register('b', [], function (exports) {
+  return {
+    execute: function () {
+      exports({
+        b: 'b'
+      });
+    }
+  };
+});

test/test.html

@@ -33,7 +33,7 @@
 			}
 		};
 
-		const extras = ['amd', 'named-exports', 'translate'];
+		const extras = ['amd', 'named-exports', 'transform', 'named-register'];
 		function runNextExtra () {
 			mocha.suite.suites.shift();
 			const extra = extras.shift();