Merge pull request #1202 from isiahmeadows/call-async

Make callAsync a little less flaky

test-utils/callAsync.js

@@ -1,3 +1,57 @@
 "use strict"
 
-module.exports = typeof setImmediate === "function" ? setImmediate : setTimeout
+/**
+ * This is modeled after Bluebird's scheduler. It solves for quite a few edge
+ * cases, and should help alleviate most of the flakiness issues. It also speeds
+ * up the suite a bit.
+ */
+
+module.exports = (function () {
+	// The scheduler for NodeJS/io.js is setImmediate for recent versions of
+	// node because of macrotask semantics (i.e. don't starve the event loop).
+	if (typeof process !== "undefined" &&
+			/^\[object process\]/i.test({}.toString.call(process))) {
+		var version = process.versions.node.split(".").map(Number)
+		var isRecent = version[0] === 0 && version[1] > 10 || version[0] > 0
+
+		return isRecent ? setImmediate : process.nextTick
+	}
+
+	if (typeof Promise === "function") {
+		var p = Promise.resolve()
+
+		return function (fn) {
+			p.then(fn)
+		}
+	}
+
+	if (typeof MutationObserver !== "undefined") {
+		// Using 2 mutation observers to batch multiple updates into one.
+		var div = document.createElement("div")
+		var opts = {attributes: true}
+		var toggleScheduled = false
+		var div2 = document.createElement("div")
+		var o2 = new MutationObserver(function() {
+			div.classList.toggle("foo")
+			toggleScheduled = false
+		})
+		o2.observe(div2, opts)
+
+		function scheduleToggle() {
+			if (toggleScheduled) return
+			toggleScheduled = true
+			div2.classList.toggle("foo")
+		}
+
+		return function (fn) {
+			var o = new MutationObserver(function() {
+				o.disconnect()
+				fn()
+			})
+			o.observe(div, opts)
+			scheduleToggle()
+		}
+	}
+
+	return typeof setImmediate === "function" ? setImmediate : setTimeout
+})()

test-utils/tests/test-callAsync.js

@@ -20,6 +20,6 @@ o.spec("callAsync", function() {
 		})
 		timeout = setTimeout(function() {
 			throw new Error("callAsync was called too slow")
-		}, 0)
+		}, 5)
 	})
-})
+})