Fix MithrilJS#2419 (MithrilJS#2421)

* Fix MithrilJS#2419

* Update the changelog

Author: dead-claudia

docs/change-log.md

@@ -40,6 +40,9 @@
 - route, request: Interpolated arguments are *not* appended to the query string. This means `m.request({url: "/api/user/:id/get", params: {id: user.id}})` would result in a request like `GET /api/user/1/get`, not one like `GET /api/user/1/get?id=1`. If you really need it in both places, pass the same value via two separate parameters with the non-query-string parameter renamed, like in `m.request({url: "/api/user/:urlID/get", params: {id: user.id, urlID: user.id}})`. ([#2361](https://github.com/MithrilJS/mithril.js/pull/2361))
 - route, request: `m.route.set`, `m.request`, and `m.jsonp` all use the same path template syntax now, and vary only in how they receive their parameters. Furthermore, declared routes in `m.route` shares the same syntax and semantics, but acts in reverse as if via pattern matching. ([#2361](https://github.com/MithrilJS/mithril.js/pull/2361))
 - request: `options.responseType` now defaults to `"json"` if `extract` is absent, and `deserialize` receives the parsed response, not the raw string. If you want the old behavior, [use `responseType: "text"`](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/responseType). ([#2335](https://github.com/MithrilJS/mithril.js/pull/2335))
+- request: set `Content-Type: application/json; charset=utf-8` for all XHR methods by default, provided they have a body that's `!= null` ([#2361](https://github.com/MithrilJS/mithril.js/pull/2361), [#2421](https://github.com/MithrilJS/mithril.js/pull/2421))
+    - This can cause CORS issues when issuing `GET` with bodies, but you can address them through configuring CORS appropriately.
+    - Previously, it was only set for all non-`GET` methods and only when `useBody: true` was passed (the default), and it was always set for them. Now it's automatically omitted when no body is present, so the hole is slightly broadened.
 
 #### News
 

request/request.js

@@ -71,7 +71,7 @@ module.exports = function($window, Promise) {
 
 			xhr.open(method, url, args.async !== false, typeof args.user === "string" ? args.user : undefined, typeof args.password === "string" ? args.password : undefined)
 
-			if (assumeJSON && !hasHeader(args, /^content-type$/i)) {
+			if (assumeJSON && body != null && !hasHeader(args, /^content-type$/i)) {
 				xhr.setRequestHeader("Content-Type", "application/json; charset=utf-8")
 			}
 			if (typeof args.deserialize !== "function" && !hasHeader(args, /^accept$/i)) {

request/tests/test-request.js

@@ -434,19 +434,6 @@ o.spec("xhr", function() {
 				o(xhr.getRequestHeader("Content-Type")).equals("Value")
 			}
 		})
-		o("json headers are set to the correct default value", function(done) {
-			mock.$defineRoutes({
-				"POST /item": function() {
-					return {status: 200, responseText: ""}
-				}
-			})
-			xhr({method: "POST", url: "/item", config: config}).then(done)
-
-			function config(xhr) {
-				o(xhr.getRequestHeader("Content-Type")).equals("application/json; charset=utf-8")
-				o(xhr.getRequestHeader("Accept")).equals("application/json, text/*")
-			}
-		})
 		o("doesn't fail on abort", function(done) {
 			mock.$defineRoutes({
 				"GET /item": function() {
@@ -640,4 +627,72 @@ o.spec("xhr", function() {
 			})
 		})
 	})
+	o.spec("json header", function() {
+		function checkUnset(method) {
+			o("doesn't set header on " + method + " without body", function(done) {
+				var routes = {}
+				routes[method + " /item"] = function() {
+					return {status: 200, responseText: JSON.stringify({a: 1})}
+				}
+				mock.$defineRoutes(routes)
+				xhr({
+					method: method, url: "/item",
+					config: function(xhr) {
+						var header = xhr.getRequestHeader("Content-Type")
+						o(header).equals(undefined)
+						header = xhr.getRequestHeader("Accept")
+						o(header).equals("application/json, text/*")
+					}
+				}).then(function(result) {
+					o(result).deepEquals({a: 1})
+					done()
+				}).catch(function(e) {
+					done(e)
+				})
+			})
+		}
+
+		function checkSet(method, body) {
+			o("sets header on " + method + " with body", function(done) {
+				var routes = {}
+				routes[method + " /item"] = function(response) {
+					return {
+						status: 200,
+						responseText: JSON.stringify({body: JSON.parse(response.body)}),
+					}
+				}
+				mock.$defineRoutes(routes)
+				xhr({
+					method: method, url: "/item", body: body,
+					config: function(xhr) {
+						var header = xhr.getRequestHeader("Content-Type")
+						o(header).equals("application/json; charset=utf-8")
+						header = xhr.getRequestHeader("Accept")
+						o(header).equals("application/json, text/*")
+					}
+				}).then(function(result) {
+					o(result).deepEquals({body: body})
+					done()
+				}).catch(function(e) {
+					done(e)
+				})
+			})
+		}
+
+		checkUnset("GET")
+		checkUnset("HEAD")
+		checkUnset("OPTIONS")
+		checkUnset("POST")
+		checkUnset("PUT")
+		checkUnset("DELETE")
+		checkUnset("PATCH")
+
+		checkSet("GET", {foo: "bar"})
+		checkSet("HEAD", {foo: "bar"})
+		checkSet("OPTIONS", {foo: "bar"})
+		checkSet("POST", {foo: "bar"})
+		checkSet("PUT", {foo: "bar"})
+		checkSet("DELETE", {foo: "bar"})
+		checkSet("PATCH", {foo: "bar"})
+	})
 })