Fix select option to use empty string value, add tests.

render/render.js

@@ -481,7 +481,7 @@ module.exports = function($window) {
 			//setting select[value] to same value while having select open blinks select dropdown in Chrome
 			if (vnode.tag === "select" && key === "value" && vnode.dom.value == value && vnode.dom === $doc.activeElement) return
 			//setting option[value] to same value while having select open blinks select dropdown in Chrome
-			if (vnode.tag === "option" && key === "value" && vnode.dom.value == value) return
+			if (vnode.tag === "option" && key === "value" && old != null && vnode.dom.value == value) return
 			// If you assign an input type that is not supported by IE 11 with an assignment expression, an error will occur.
 			if (vnode.tag === "input" && key === "type") {
 				element.setAttribute(key, value)

render/tests/test-input.js

@@ -90,6 +90,47 @@ o.spec("form inputs", function() {
 			o(select.dom.firstChild.value).equals("")
 		})
 
+		o("option value defaults to textContent unless explicitly set", function() {
+			var select = {tag: "select", children :[
+				{tag: "option", text: "aaa"}
+			]}
+
+			render(root, [select])
+
+			o(select.dom.firstChild.value).equals("aaa")
+			o(select.dom.value).equals("aaa")
+
+			//test that value changes when content changes
+			select = {tag: "select", children :[
+				{tag: "option", text: "bbb"}
+			]}
+
+			render(root, [select])
+
+			o(select.dom.firstChild.value).equals("bbb")
+			o(select.dom.value).equals("bbb")
+
+			//test that value can be set to "" in subsequent render
+			select = {tag: "select", children :[
+				{tag: "option", attrs: {value: ""}, text: "aaa"}
+			]}
+
+			render(root, [select])
+
+			o(select.dom.firstChild.value).equals("")
+			o(select.dom.value).equals("")
+
+			//test that value reverts to textContent when value omitted
+			select = {tag: "select", children :[
+				{tag: "option", text: "ccc"}
+			]}
+
+			render(root, [select])
+
+			o(select.dom.firstChild.value).equals("ccc")
+			o(select.dom.value).equals("ccc")
+		})
+
 		o("select yields invalid value without children", function() {
 			var select = {tag: "select", attrs: {value: "a"}}