From 75032f0a8de1096ffd5895b2a99c96f9adf887f4 Mon Sep 17 00:00:00 2001
From: Rodrigo Palhares <rodrigo.palhares@hotmart.com.br>
Date: Fri, 30 Sep 2016 15:52:18 -0300
Subject: [PATCH] observer-sequence: Bug, array with null values. fixes #7850

---
 packages/observe-sequence/observe_sequence.js       | 5 +++--
 packages/observe-sequence/observe_sequence_tests.js | 9 +++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/packages/observe-sequence/observe_sequence.js b/packages/observe-sequence/observe_sequence.js
index 0ba750bcf5..1a823ab019 100644
--- a/packages/observe-sequence/observe_sequence.js
+++ b/packages/observe-sequence/observe_sequence.js
@@ -289,7 +289,8 @@ seqChangedToArray = function (lastSeqArray, array, callbacks) {
       id = "-" + item;
     } else if (typeof item === 'number' ||
                typeof item === 'boolean' ||
-               item === undefined) {
+               item === undefined ||
+               item === null) {
       id = item;
     } else if (typeof item === 'object') {
       id = (item && ('_id' in item)) ? item._id : index;
@@ -300,7 +301,7 @@ seqChangedToArray = function (lastSeqArray, array, callbacks) {
 
     var idString = idStringify(id);
     if (idsUsed[idString]) {
-      if (typeof item === 'object' && '_id' in item)
+      if (item && typeof item === 'object' && '_id' in item)
         warn("duplicate id " + id + " in", array);
       id = Random.id();
     } else {
diff --git a/packages/observe-sequence/observe_sequence_tests.js b/packages/observe-sequence/observe_sequence_tests.js
index 4e126eca8f..e6a6ed823d 100644
--- a/packages/observe-sequence/observe_sequence_tests.js
+++ b/packages/observe-sequence/observe_sequence_tests.js
@@ -177,6 +177,15 @@ Tinytest.add('observe-sequence - array to other array, strings', function (test)
   ]);
 });
 
+Tinytest.add('observe-sequence - bug #7850 array with null values', function (test) {
+  runOneObserveSequenceTestCase(test, function () {
+    return [1, null];
+  }, function () {}, [
+    {addedAt: [1, 1, 0, null]},
+    {addedAt: [null, null, 1, null]}
+  ]);
+});
+
 Tinytest.add('observe-sequence - array to other array, objects without ids', function (test) {
   var dep = new Tracker.Dependency;
   var seq = [{foo: 1}, {bar: 2}];