Somewhat smarter way of knowing whether we should send JSON or not. S…

…hould fix #130 (it's never too late)

lib/needle.js

@@ -263,6 +263,9 @@ Needle.prototype.start = function() {
 
   var body, config = this.setup(uri, options);
 
+  // assume boss wants JSON either if json is true, or if content-type was set and JSON ain't false (weird).
+  var json = options.json || (options.json !== false && config.headers['content-type'] == 'application/json');
+
   if (data) {
 
     if (options.multipart) { // boss says we do multipart. so we do it.
@@ -286,7 +289,7 @@ Needle.prototype.start = function() {
 
       body = data; // use the raw buffer or stream as request body.
 
-    } else if (method.toUpperCase() == 'GET' && !options.json) {
+    } else if (method.toUpperCase() == 'GET' && !json) {
 
       // append the data to the URI as a querystring.
       uri = uri.replace(/\?.*|$/, '?' + stringify(data));
@@ -295,7 +298,7 @@ Needle.prototype.start = function() {
 
       // if string, leave it as it is, otherwise, stringify.
       body = (typeof(data) === 'string') ? data
-             : options.json ? JSON.stringify(data) : stringify(data);
+             : json ? JSON.stringify(data) : stringify(data);
 
       // ensure we have a buffer so bytecount is correct.
       body = new Buffer(body, config.encoding);
@@ -309,12 +312,12 @@ Needle.prototype.start = function() {
 
     // if no content-type was passed, determine if json or not.
     if (!config.headers['content-type']) {
-      config.headers['content-type'] = options.json
+      config.headers['content-type'] = json
       ? 'application/json; charset=utf-8'
       : 'application/x-www-form-urlencoded'; // no charset says W3 spec.
     }
 
-    // unless a specific accept header was passed, assume json wants json back.
+    // unless a specific accept header is set, assume json:true wants json back.
     if (options.json && config.headers['accept'] === defaults.accept)
       config.headers['accept'] = 'application/json';
   }

test/post_data_spec.js

@@ -593,6 +593,44 @@ describe('post data (e.g. request body)', function() {
 
         })
 
+        describe('with json: undefined but content-type = application/json', function() {
+
+          var opts = { headers: { 'content-type': 'application/json' } };
+
+          it('sends request', function(done) {
+            spystub_request();
+
+            post({ foo: 'bar', test: '测试' }, opts, function(err, resp) {
+              check_request('post');
+              done();
+            })
+          })
+
+          it('doesnt change Content-Type header', function(done) {
+            post({ foo: 'bar', test: '测试' }, opts, function(err, resp) {
+              resp.body.headers['content-type'].should.equal('application/json');
+              done();
+            })
+          })
+
+          it('leaves default Accept header', function(done) {
+            post({ foo: 'bar', test: '测试' }, opts, function(err, resp) {
+              resp.body.headers['accept'].should.equal('*/*');
+              done();
+            })
+          })
+
+          it('writes JSON.stringified object', function(done) {
+            post({ foo: 'bar', test: '测试' }, opts, function(err, resp) {
+              spy.called.should.be.true;
+              var json = JSON.stringify({ foo: 'bar', test: '测试' })
+              spy.args[0][0].toString().should.eql(json)
+              resp.body.body.should.eql(json);
+              done();
+            })
+          })
+        })
+
         describe('with json: true', function() {
 
           it('sends request', function(done) {
@@ -781,7 +819,7 @@ describe('post data (e.g. request body)', function() {
             })
           })
 
-          it('writes JSON.stringified object', function(done) {
+          it('passes raw buffer (assuming its a JSON string beneath)', function(done) {
             post(new Buffer('foobar'), { json: true }, function(err, resp) {
               spy.called.should.be.true;
               spy.args[0][0].toString().should.eql('foobar')