Allow deletion of uninstantiated modules whose top level parent import finished. Resolves #2286. (#2291)

* Reproduce issue #2286.

* Making test more clear

* Fix

* Self review

* Add load.p

* possible parent fix

* optional p

* parent restriction

* Fix

* Update src/system-core.js

* another variation

Co-authored-by: Guy Bedford <guybedford@gmail.com>

src/features/registry.js

@@ -67,7 +67,7 @@ systemJSPrototype.delete = function (id) {
   var load = registry[id];
   // in future we can support load.E case by failing load first
   // but that will require TLA callbacks to be implemented
-  if (!load || load.e !== null || load.E)
+  if (!load || (load.p && load.p.e !== null) || load.E)
     return false;
 
   var importerSetters = load.i;

src/system-core.js

@@ -186,8 +186,6 @@ export function getOrCreateLoad (loader, id, firstParentUrl) {
     // dependency load records
     d: undefined,
     // execution function
-    // set to NULL immediately after execution (or on any failure) to indicate execution has happened
-    // in such a case, C should be used, and E, I, L will be emptied
     e: undefined,
 
     // On execution we have populated:
@@ -199,18 +197,23 @@ export function getOrCreateLoad (loader, id, firstParentUrl) {
     // On execution, L, I, E cleared
 
     // Promise for top-level completion
-    C: undefined
+    C: undefined,
+
+    // parent instantiator / executor
+    p: undefined
   };
 }
 
-function instantiateAll (loader, load, loaded) {
+function instantiateAll (loader, load, parent, loaded) {
   if (!loaded[load.id]) {
     loaded[load.id] = true;
     // load.L may be undefined for already-instantiated
     return Promise.resolve(load.L)
     .then(function () {
+      if (!load.p || load.p.e === null)
+        load.p = parent;
       return Promise.all(load.d.map(function (dep) {
-        return instantiateAll(loader, dep, loaded);
+        return instantiateAll(loader, dep, parent, loaded);
       }));
     })
     .catch(function (err) {
@@ -224,7 +227,7 @@ function instantiateAll (loader, load, loaded) {
 }
 
 function topLevelLoad (loader, load) {
-  return load.C = instantiateAll(loader, load, {})
+  return load.C = instantiateAll(loader, load, load, {})
   .then(function () {
     return postOrderExec(loader, load, {});
   })

test/browser/core.js

@@ -313,6 +313,7 @@ suite('SystemJS Standard Tests', function() {
         assert.ok(System.delete(System.resolve('fixtures/link-error.js')));
         assert.ok(System.delete(System.resolve('fixtures/link-error-child.js')));
         assert.ok(System.delete(System.resolve('fixtures/not-found.js')));
+        assert.ok(System.delete(System.resolve('fixtures/link-error-child2.js')));
       }
     );
   });

test/fixtures/browser/link-error-child2.js

@@ -0,0 +1,7 @@
+System.register([], function (_export) {
+  return {
+    execute: function () {
+      _export('default', 'link-error-child2 instantiated successfully');
+    }
+  };
+});

test/fixtures/browser/link-error.js

@@ -1,4 +1,4 @@
-System.register(['./link-error-child.js'], function () {
+System.register(['./link-error-child.js', './link-error-child2.js'], function () {
   return {
     execute: function () {
     }