Merge pull request #734 from dgilland/feature-propify-finally

Add `finally` to promise-like object.

mithril.js

@@ -1055,6 +1055,14 @@ var m = (function app(window, undefined) {
 			return propify(promise.then(resolve, reject), initialValue);
 		};
 		prop["catch"] = prop.then.bind(null, null);
+		prop["finally"] = function(callback){
+			var _callback = function(value){return m.deferred().resolve(callback(value)).promise;};
+			return prop.then(function(value) {
+				return propify(_callback(value).then(function() {return value;}), initialValue);
+			}, function(reason) {
+				return propify(_callback(reason).then(function() {throw new Error(reason);}), initialValue);
+			});
+		};
 		return prop;
 	}
 	//Promiz.mithril.js | Zolmeister | MIT

tests/mithril-tests.js

@@ -3915,6 +3915,35 @@ function testMithril(mock) {
 		mock.XMLHttpRequest.$instances.pop().onreadystatechange()
 		return prop().message === "error occurred" && error().message === "error occurred"
 	})
+	test(function() {
+		// Data returned by then() functions propagate to finally().
+		var data = m.prop("");
+		var prop = m.request({method: "GET", url: "test"}).then(function() {return "foo"})["finally"](data)
+		mock.XMLHttpRequest.$instances.pop().onreadystatechange()
+		return prop() === "foo" && data() === "foo"
+	})
+	test(function() {
+		// Data returned by finally() functions do *not* propagate to next promise.
+		var data = m.prop("");
+		var prop = m.request({method: "GET", url: "test"}).then(function() {return "foo"})["finally"](function() {return "bar"}).then(data)
+		mock.XMLHttpRequest.$instances.pop().onreadystatechange()
+		return prop() === "foo" && data() === "foo"
+	})
+	test(function() {
+		// Errors thrown in finally() can be caught by next promise.
+		var error = m.prop("no error")
+		var prop = m.request({method: "GET", url: "test"}).then(function() {return "foo"})["finally"](function() {throw new Error("error occurred")})["catch"](error)
+		mock.XMLHttpRequest.$instances.pop().onreadystatechange()
+		return prop().message === "error occurred" && error().message === "error occurred"
+	})
+	test(function() {
+		// Promise finally() method occurrs after catch().
+		var error = m.prop("no error")
+		var lastly = function() { error("lastly") };
+		var prop = m.request({method: "GET", url: "test", deserialize: function() {throw new Error("error occurred")}})["catch"](error)["finally"](lastly)
+		mock.XMLHttpRequest.$instances.pop().onreadystatechange()
+		return prop().message === "error occurred" && error() === "lastly"
+	})
 	test(function() {
 		var error = m.prop("no error"), exception
 		var prop = m.request({method: "GET", url: "test", deserialize: function() {throw new TypeError("error occurred")}}).then(null, error)