instead of exporter lock, use exporter cache as implicit lock mechanism, enabling full circlar reference binding update cases

Author: guybedford

core/register-loader.js

@@ -326,35 +326,40 @@ function registerDeclarative (loader, load, link, declare) {
   var moduleObj = link.moduleObj;
   var importerSetters = load.importerSetters;
 
-  var locked = false;
+  var definedExports = false;
 
   // closure especially not based on link to allow link record disposal
   var declared = declare.call(global, function (name, value) {
-    // export setter propogation with locking to avoid cycles
-    if (locked)
-      return;
-
     if (typeof name === 'object') {
-      for (var p in name)
-        if (p !== '__useDefault')
-          moduleObj[p] = name[p];
+      var changed = false;
+      for (var p in name) {
+        value = name[p];
+        if (p !== '__useDefault' && (!(p in moduleObj) || moduleObj[p] !== value)) {
+          changed = true;
+          moduleObj[p] = value;
+        }
+      }
+      if (changed === false)
+        return;
     }
     else {
+      if ((definedExports || name in moduleObj) && moduleObj[name] === value)
+        return;
       moduleObj[name] = value;
     }
 
-    locked = true;
     for (var i = 0; i < importerSetters.length; i++)
       importerSetters[i](moduleObj);
-    locked = false;
 
     return value;
   }, new ContextualLoader(loader, load.key));
 
   link.setters = declared.setters;
   link.execute = declared.execute;
-  if (declared.exports)
+  if (declared.exports) {
     link.moduleObj = moduleObj = declared.exports;
+    definedExports = true;
+  }
 }
 
 function instantiateDeps (loader, load, link, registry, state, seen) {

test/3-register-loader.js

@@ -77,14 +77,16 @@ describe('System Register Loader', function() {
       var m1 = await loader.import('./register-modules/circular1.js');
       var m2 = await loader.import('./register-modules/circular2.js');
 
-
       assert.equal(m1.variable1, 'test circular 1');
       assert.equal(m2.variable2, 'test circular 2');
 
       assert.equal(m2.output, 'test circular 1');
       assert.equal(m1.output, 'test circular 2');
       assert.equal(m2.output1, 'test circular 2');
       assert.equal(m1.output2, 'test circular 1');
+
+      assert.equal(m1.output1, 'test circular 2');
+      assert.equal(m2.output2, 'test circular 1');
     });
 
     it('should update circular dependencies', async function () {

test/fixtures/es-modules/circular1.js

@@ -2,12 +2,12 @@ import {fn2, variable2} from './circular2.js';
 
 export var variable1 = 'test circular 1';
 
-export { output as output2 } from './circular2.js';
-
-fn2();
+export { output as output2, output1 } from './circular2.js';
 
 export var output;
 
+fn2();
+
 export function fn1() {
   output = variable2;
-}
+}

test/fixtures/es-modules/circular2.js

@@ -2,12 +2,12 @@ import {fn1, variable1} from './circular1.js';
 
 export var variable2 = 'test circular 2';
 
-export { output as output1 } from './circular1.js';
-
-fn1();
+export { output as output1, output2 } from './circular1.js';
 
 export var output;
 
+fn1();
+
 export function fn2() {
   output = variable1;
-}
+}

test/fixtures/register-modules/circular1.js

@@ -6,18 +6,22 @@ System.register(['./circular2.js'], function (_export, _context) {
     _export('output', output = variable2);
   }
 
+  _export('fn1', fn1);
+
   return {
     exports: {
       fn1: fn1,
       variable1: undefined,
       output: undefined,
+      output1: undefined,
       output2: undefined
     },
     setters: [function (_circular2Js) {
       fn2 = _circular2Js.fn2;
       variable2 = _circular2Js.variable2;
       var _exportObj = {};
       _exportObj.output2 = _circular2Js.output;
+      _exportObj.output1 = _circular2Js.output1;
 
       _export(_exportObj);
     }],
@@ -26,9 +30,9 @@ System.register(['./circular2.js'], function (_export, _context) {
 
       _export('variable1', variable1);
 
-      fn2();
-
       _export('output', output);
+
+      fn2();
     }
   };
 });

test/fixtures/register-modules/circular2.js

@@ -14,6 +14,7 @@ System.register(['./circular1.js'], function (_export, _context) {
       variable1 = _circular1Js.variable1;
       var _exportObj = {};
       _exportObj.output1 = _circular1Js.output;
+      _exportObj.output2 = _circular1Js.output2;
 
       _export(_exportObj);
     }],
@@ -22,9 +23,9 @@ System.register(['./circular1.js'], function (_export, _context) {
 
       _export('variable2', variable2);
 
-      fn1();
-
       _export('output', output);
+
+      fn1();
     }
   };
 });