[BUGFIX release-1-13] Ensure concat streams unsubscribe properly.

packages/ember-metal/lib/streams/utils.js

@@ -183,7 +183,7 @@ export function concat(array, separator) {
     });
 
     for (i = 0, l = array.length; i < l; i++) {
-      subscribe(array[i], stream.notify, stream);
+      stream.addDependency(array[i]);
     }
 
     // used by angle bracket components to detect an attribute was provided

packages/ember-metal/tests/streams/concat_test.js

@@ -0,0 +1,63 @@
+import Stream from 'ember-metal/streams/stream';
+import {
+  concat,
+  read
+} from 'ember-metal/streams/utils';
+
+
+function hasSubscribers(stream) {
+  // this uses the private internal property `subscriberHead`
+  // for the purposes of ensuring that subscription is cleared
+  // after deactivation.  Adding a util helper to the `Stream` code
+  // just for the test seems dubious, as does accessing the private
+  // property directly in the test.
+  return stream && !!stream.subscriberHead;
+}
+
+QUnit.module('Stream - concat');
+
+QUnit.test('returns string if no streams were in the array', function(assert) {
+  let result = concat(['foo', 'bar', 'baz'], ' ');
+
+  assert.equal(result, 'foo bar baz');
+});
+
+QUnit.test('returns a stream if a stream is in the array', function(assert) {
+  let stream = new Stream(function() {
+    return 'bar';
+  });
+  let result = concat(['foo', stream, 'baz'], ' ');
+
+  assert.ok(result.isStream, 'a stream is returned');
+  assert.equal(read(result), 'foo bar baz');
+});
+
+QUnit.test('returns updated value upon input dirtied', function(assert) {
+  let value = 'bar';
+  let stream = new Stream(function() {
+    return value;
+  });
+  let result = concat(['foo', stream, 'baz'], ' ');
+  result.activate();
+
+  assert.equal(read(result), 'foo bar baz');
+
+  value = 'qux';
+  stream.notify();
+
+  assert.equal(read(result), 'foo qux baz');
+});
+
+QUnit.test('removes dependencies when unsubscribeDependencies is called', function(assert) {
+  let stream = new Stream(function() {
+    return 'bar';
+  });
+  let result = concat(['foo', stream, 'baz'], ' ');
+  result.activate();
+
+  assert.equal(hasSubscribers(stream), true, 'subscribers are present from the concat stream');
+
+  result.maybeDeactivate();
+
+  assert.equal(hasSubscribers(stream), false, 'subscribers are removed after concat stream is deactivated');
+});