From 984dcd1c0fe8a83f83165294546108b87cebc302 Mon Sep 17 00:00:00 2001
From: Joel Denning <joeldenning@gmail.com>
Date: Sun, 7 Apr 2019 11:07:28 -0600
Subject: [PATCH] Making the registry iterable. See #1918. (#1919)

---
 docs/api.md              | 16 ++++++++++++++++
 src/features/registry.js | 23 ++++++++++++++++++++++-
 test/system-core.js      | 21 +++++++++++++++++++++
 3 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/docs/api.md b/docs/api.md
index ae5af7cfb..8282631d2 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -87,3 +87,19 @@ System.set('http://site.com/normalized/module/name.js', {
 `module` is an object of names to set as the named exports.
 
 If `module` is an existing Module Namespace, it will be used by reference.
+
+#### System.entries() -> Array
+Type: `Function`
+
+Allows you to retrieve all modules in the System registry. Each value will be an array with two values: a key and the module. Also available
+at `System[Symbol.iterator]`.
+
+```js
+System.entries().forEach((key, value) => {
+  console.log(entry); // ['http://localhost/path-to-file.js', {exportName: 'exportedValue'}]
+});
+
+for (let entry of System) {
+  console.log(entry); // ['http://localhost/path-to-file.js', {exportName: 'exportedValue'}]
+}
+```
\ No newline at end of file
diff --git a/src/features/registry.js b/src/features/registry.js
index aed89b63e..3f1aa3636 100644
--- a/src/features/registry.js
+++ b/src/features/registry.js
@@ -58,4 +58,25 @@ systemJSPrototype.delete = function (id) {
         depLoad.i.splice(importerIndex, 1);
     });
   return delete this[REGISTRY][id];
-};
\ No newline at end of file
+};
+
+systemJSPrototype.entries = function () {
+  const registry = this[REGISTRY];
+  return Object.keys(registry).map(function (key) {
+    return [key, registry[key].n];
+  });
+}
+
+if (typeof Symbol !== 'undefined') {
+  systemJSPrototype[Symbol.iterator] = function () {
+    const registry = this[REGISTRY];
+    const keys = Object.keys(registry);
+    let index = 0;
+    return {
+      next() {
+        const key = keys[index++];
+        return { done: index > keys.length, value: key && [key, registry[key].n] };
+      }
+    };
+  }
+}
\ No newline at end of file
diff --git a/test/system-core.js b/test/system-core.js
index 6421e8787..59bf22d6c 100644
--- a/test/system-core.js
+++ b/test/system-core.js
@@ -137,6 +137,27 @@ describe('Core API', function () {
       assert(resolveReturnValue instanceof Promise);
       assert.equal(resolvedX, 'http://x');
     });
+
+    it('Supports iteration', async function () {
+      loader.set('h', {a: 'b'});
+      await loader.import('h');
+
+      let foundH = false;
+      for (let entry of loader) {
+        if (entry[0] === 'h' && entry[1].a === 'b') {
+          foundH = true;
+        }
+      }
+
+      assert(foundH);
+    });
+
+    it('Supports System.entries', async function () {
+      loader.set('i', {a: 'b'});
+      await loader.import('i');
+
+      assert(loader.entries().some(entry => entry[0] === 'i' && entry[1].a === 'b'));
+    })
   });
 });