allow string keys

mithril.js

@@ -442,11 +442,10 @@ var m = (function app(window, undefined) {
 
 	function checkView(data, view, cached, cachedControllers, controllers, views) {
 		var controller = getController(cached.views, view, cachedControllers, data.controller);
-		//Faster to coerce to number and check for NaN
-		var key = +(data && data.attrs && data.attrs.key);
+		var key = data && data.attrs && data.attrs.key;
 		data = pendingRequests === 0 || forcing || cachedControllers && cachedControllers.indexOf(controller) > -1 ? data.view(controller) : {tag: "placeholder"};
 		if (data.subtree === "retain") return data;
-		if (key === key) (data.attrs = data.attrs || {}).key = key;
+		(data.attrs = data.attrs || {}).key = key;
 		updateLists(views, controllers, view, controller);
 		return data;
 	}

tests/mithril-tests.js

@@ -269,6 +269,41 @@ function testMithril(mock) {
 
 		return firstBefore === firstAfter
 	})
+	test(function() {
+		//string keys in components should work
+		mock.requestAnimationFrame.$resolve()
+
+		var root = mock.document.createElement("div")
+		var list = [1, 2, 3]
+		var component = {
+			controller: function() {},
+			view: function() {
+				return list.map(function(i) {
+					return m.component(sub, {key: "key" + i})
+				})
+			}
+		}
+		var sub = {
+			controller: function() {},
+			view: function() {
+				return m("div")
+			}
+		}
+		m.mount(root, component)
+
+		var firstBefore = root.childNodes[0]
+
+		mock.requestAnimationFrame.$resolve()
+
+		list.reverse()
+		m.redraw(true)
+
+		mock.requestAnimationFrame.$resolve()
+
+		var firstAfter = root.childNodes[2]
+
+		return firstBefore === firstAfter
+	})
 	test(function() {
 		//keys in subcomponents should work
 		mock.requestAnimationFrame.$resolve()