feat(Scope): async auto-flush $evalAsync queue when outside of $digest

This change causes a new $digest to be scheduled in the next tick if
a task was was sent to the $evalAsync queue from outside of a $digest
or an $apply.

While this mode of operation is not common for most of the user code,
this change means that $q promises that utilze $evalAsync queue to
guarantee asynchronicity of promise apis will now also resolve outside
of a $digest, which turned out to be a big pain point for some developers.

The implementation ensures that we don't do more work than needed and
that we coalese as much work as possible into a single $digest.

The use of $browser instead of setTimeout ensures that we can mock out
and control the scheduling of "auto-flush", which should in theory
allow all of the existing code and tests to work without negative
side-effects.

Closes #3539
Closes #2438

1 files changed, 51 insertions, 0 deletions

diff --git a/test/ng/rootScopeSpec.js b/test/ng/rootScopeSpec.js
index ddd83088..0a85d9a8 100644
--- a/test/ng/rootScopeSpec.js
+++ b/test/ng/rootScopeSpec.js
@@ -705,6 +705,57 @@ describe('Scope', function() {
       expect(isolateScope.$$asyncQueue).toBe($rootScope.$$asyncQueue);
       expect($rootScope.$$asyncQueue).toEqual(['rootExpression', 'childExpression', 'isolateExpression']);
     }));
+
+
+    describe('auto-flushing when queueing outside of an $apply', function() {
+      var log, $rootScope, $browser;
+
+      beforeEach(inject(function(_log_, _$rootScope_, _$browser_) {
+        log = _log_;
+        $rootScope = _$rootScope_;
+        $browser = _$browser_;
+      }));
+
+
+      it('should auto-flush the queue asynchronously and trigger digest', function() {
+        $rootScope.$evalAsync(log.fn('eval-ed!'));
+        $rootScope.$watch(log.fn('digesting'));
+        expect(log).toEqual([]);
+
+        $browser.defer.flush(0);
+
+        expect(log).toEqual(['eval-ed!', 'digesting', 'digesting']);
+      });
+
+
+      it('should not trigger digest asynchronously if the queue is empty in the next tick', function() {
+        $rootScope.$evalAsync(log.fn('eval-ed!'));
+        $rootScope.$watch(log.fn('digesting'));
+        expect(log).toEqual([]);
+
+        $rootScope.$digest();
+
+        expect(log).toEqual(['eval-ed!', 'digesting', 'digesting']);
+        log.reset();
+
+        $browser.defer.flush(0);
+
+        expect(log).toEqual([]);
+      });
+
+
+      it('should not schedule more than one auto-flush task', function() {
+        $rootScope.$evalAsync(log.fn('eval-ed 1!'));
+        $rootScope.$evalAsync(log.fn('eval-ed 2!'));
+
+        $browser.defer.flush(0);
+        expect(log).toEqual(['eval-ed 1!', 'eval-ed 2!']);
+
+        expect(function() {
+          $browser.defer.flush(0);
+        }).toThrow('No deferred tasks with delay up to 0ms to be flushed!');
+      });
+    });
   });