From 1f44e00c5069e965b85fd4147cebd977d3324a55 Mon Sep 17 00:00:00 2001
From: Peter Burns <rictic@google.com>
Date: Sun, 25 Sep 2016 14:01:30 -0700
Subject: [PATCH] Add support for cloning Promises

---
 clone.js | 17 +++++++++++++++--
 test.js  | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+), 2 deletions(-)

diff --git a/clone.js b/clone.js
index aa97478..2c8f65a 100644
--- a/clone.js
+++ b/clone.js
@@ -14,11 +14,16 @@ var nativeSet;
 try {
   nativeSet = Set;
 } catch(_) {
-  // maybe a reference error because no `Set`. Give it a dummy value that no
-  // value will ever be an instanceof.
   nativeSet = function() {};
 }
 
+var nativePromise;
+try {
+  nativePromise = Promise;
+} catch(_) {
+  nativePromise = function() {};
+}
+
 /**
  * Clones (copies) an Object using deep copying.
  *
@@ -77,6 +82,14 @@ function clone(parent, circular, depth, prototype) {
       child = new nativeMap();
     } else if (parent instanceof nativeSet) {
       child = new nativeSet();
+    } else if (parent instanceof nativePromise) {
+      child = new nativePromise(function (resolve, reject) {
+        parent.then(function(value) {
+          resolve(_clone(value, depth - 1));
+        }, function(err) {
+          reject(_clone(err, depth - 1));
+        });
+      });
     } else if (clone.__isArray(parent)) {
       child = [];
     } else if (clone.__isRegExp(parent)) {
diff --git a/test.js b/test.js
index 5de1923..984ea72 100644
--- a/test.js
+++ b/test.js
@@ -427,3 +427,61 @@ if (nativeSet) {
     test.done();
   }
 }
+
+var nativePromise;
+try {
+  nativePromise = Promise;
+} catch(_) {}
+if (nativePromise) {
+  exports["clone a native Promise"] = function (test) {
+    test.expect(9);
+
+    var allDonePromises = [];
+
+    // Resolving to a value
+    allDonePromises.push(
+      clone(Promise.resolve('foo')).then(function (value) {
+        test.equal(value, 'foo');
+      })
+    );
+
+    // Rejecting to a value
+    allDonePromises.push(
+      clone(Promise.reject('bar')).catch(function (value) {
+        test.equal(value, 'bar');
+      })
+    );
+
+    // Resolving to a promise
+    allDonePromises.push(
+      clone(Promise.resolve(Promise.resolve('baz'))).then(function (value) {
+        test.equal(value, 'baz');
+      })
+    );
+
+    // Resolving to a circular value
+    var circle = {};
+    circle.circle = circle;
+    allDonePromises.push(
+      clone(Promise.resolve(circle)).then(function (value) {
+        test.notEqual(circle, value);
+        test.equal(value.circle, value);
+      })
+    );
+
+    var expandoPromise = Promise.resolve('ok');
+    expandoPromise.circle = expandoPromise;
+    expandoPromise.prop = 'val';
+    var clonedPromise = clone(expandoPromise);
+    test.notEqual(expandoPromise, clonedPromise);
+    test.equal(clonedPromise.prop, 'val');
+    test.equal(clonedPromise.circle, clonedPromise);
+    allDonePromises.push(clonedPromise.then(function(value) {
+      test.equal(value, 'ok');
+    }));
+
+    Promise.all(allDonePromises).then(function() {
+      test.done();
+    });
+  }
+}
\ No newline at end of file