Fix automatic parsing of JSON responses in $.get/post

Due to a bug in `parseArguments`, `dataType` would never be null, even
when not passed as an argument, and therefore content-type–based
processing would never kick in.

Fixes #693

src/ajax.js

@@ -276,12 +276,13 @@
 
   // handle optional data/success arguments
   function parseArguments(url, data, success, dataType) {
-    var hasData = !$.isFunction(data)
+    if ($.isFunction(data)) dataType = success, success = data, data = undefined
+    if (!$.isFunction(success)) dataType = success, success = undefined
     return {
-      url:      url,
-      data:     hasData  ? data : undefined,
-      success:  !hasData ? data : $.isFunction(success) ? success : undefined,
-      dataType: hasData  ? dataType || success : success
+      url: url
+    , data: data
+    , success: success
+    , dataType: dataType
     }
   }
 

test/ajax.html

@@ -218,6 +218,30 @@ <h1>Zepto Ajax unit tests</h1>
         $.get('echo', { sample: 'plain' }, 'text')
       },
 
+      testAjaxGetWithParamsAutoParsesJSON: function(t) {
+        t.pause()
+        $.get('json', { sample: 'data' }, t.reg.resumeHandler('success', function(data){
+          t.assertEqual('data', data.query.sample)
+          t.assertEqual('world', data.hello)
+        }))
+      },
+
+      testAjaxGetNoParamsAutoParsesJSON: function(t) {
+        t.pause()
+        $.get('json', t.reg.resumeHandler('success', function(data){
+          t.assertIdentical(0, $.map(data.query).length)
+          t.assertEqual('world', data.hello)
+        }))
+      },
+
+      testAjaxGetNullParamsAutoParsesJSON: function(t) {
+        t.pause()
+        $.get('json', null, t.reg.resumeHandler('success', function(data){
+          t.assertIdentical(0, $.map(data.query).length)
+          t.assertEqual('world', data.hello)
+        }))
+      },
+
       testAjaxBeforeSendSetRequestHeader: function(t){
         t.pause()
         $.ajax({
@@ -254,6 +278,14 @@ <h1>Zepto Ajax unit tests</h1>
         }), 'text')
       },
 
+      testAjaxPostAutoParsesJSON: function(t) {
+        t.pause()
+        var payload = { sample: 'data' }
+        $.post('create', payload, t.reg.resumeHandler('success', function(data){
+          t.assertEqual('data', data.payload.sample)
+        }))
+      },
+
       testNumberOfActiveRequests: function(t) {
         var maxActive = 0, ajaxStarted = 0, ajaxEnded = 0, requestsCompleted = 0
         t.assertIdentical(0, $.active, 'initial count mismatch')

test/server.coffee

@@ -71,7 +71,8 @@ app.get '/test/jsonpBlah', (req, res) ->
 
 app.get '/test/json', (req, res) ->
   res.set 'Cache-Control', 'no-cache'
-  if /json/.test req.headers['accept']
+  expectedType = req.headers['accept']
+  if expectedType is '*/*' or /json/.test expectedType
     if req.query.invalid
       res.set 'Content-Type', 'application/json'
       res.send 'invalidJSON'
@@ -82,6 +83,12 @@ app.get '/test/json', (req, res) ->
   else
     res.send 400, 'FAIL'
 
+app.post '/test/create', (req, res) ->
+  res.json
+    action: 'created'
+    query: req.query
+    payload: req.body
+
 app.all '/test/slow', (req, res) ->
   setTimeout ->
     res.send 'DONE'