fix(headers): fixed common Content-Type header merging; (#5832)

lib/core/Axios.js

@@ -73,15 +73,13 @@ class Axios {
     // Set config.method
     config.method = (config.method || this.defaults.method || 'get').toLowerCase();
 
-    let contextHeaders;
-
     // Flatten headers
-    contextHeaders = headers && utils.merge(
+    let contextHeaders = headers && utils.merge(
       headers.common,
       headers[config.method]
     );
 
-    contextHeaders && utils.forEach(
+    headers && utils.forEach(
       ['delete', 'get', 'head', 'post', 'put', 'patch', 'common'],
       (method) => {
         delete headers[method];

lib/defaults/index.js

@@ -8,10 +8,6 @@ import toURLEncodedForm from '../helpers/toURLEncodedForm.js';
 import platform from '../platform/index.js';
 import formDataToJSON from '../helpers/formDataToJSON.js';
 
-const DEFAULT_CONTENT_TYPE = {
-  'Content-Type': undefined
-};
-
 /**
  * It takes a string, tries to parse it, and if it fails, it returns the stringified version
  * of the input
@@ -150,17 +146,14 @@ const defaults = {
 
   headers: {
     common: {
-      'Accept': 'application/json, text/plain, */*'
+      'Accept': 'application/json, text/plain, */*',
+      'Content-Type': undefined
     }
   }
 };
 
-utils.forEach(['delete', 'get', 'head'], function forEachMethodNoData(method) {
+utils.forEach(['delete', 'get', 'head', 'post', 'put', 'patch'], (method) => {
   defaults.headers[method] = {};
 });
 
-utils.forEach(['post', 'put', 'patch'], function forEachMethodWithData(method) {
-  defaults.headers[method] = utils.merge(DEFAULT_CONTENT_TYPE);
-});
-
 export default defaults;

test/specs/defaults.spec.js

@@ -151,12 +151,12 @@ describe('defaults', function () {
 
     getAjaxRequest().then(function (request) {
       expect(request.requestHeaders).toEqual(
-        utils.merge(defaults.headers.common, defaults.headers.get, {
+        AxiosHeaders.concat(defaults.headers.common, defaults.headers.get, {
           'X-COMMON-HEADER': 'commonHeaderValue',
           'X-GET-HEADER': 'getHeaderValue',
           'X-FOO-HEADER': 'fooHeaderValue',
           'X-BAR-HEADER': 'barHeaderValue'
-        })
+        }).toJSON()
       );
       done();
     });

test/specs/headers.spec.js

@@ -1,3 +1,5 @@
+import assert from "assert";
+
 const {AxiosHeaders} = axios;
 
 function testHeaderValue(headers, key, val) {
@@ -44,18 +46,35 @@ describe('headers', function () {
     });
   });
 
-  it('should add extra headers for post', function (done) {
-    const headers = axios.defaults.headers.common;
+  it('should respect common Content-Type header', function () {
+    const instance = axios.create();
+
+    instance.defaults.headers.common['Content-Type'] = 'application/custom';
+
+    instance.patch('/foo', "");
+
+    const expectedHeaders = {
+      'Content-Type': "application/custom"
+    };
+
+    return getAjaxRequest().then(function (request) {
+      for (const key in expectedHeaders) {
+        if (expectedHeaders.hasOwnProperty(key)) {
+          expect(request.requestHeaders[key]).toEqual(expectedHeaders[key]);
+        }
+      }
+    });
+  });
+
+  it('should add extra headers for post', function () {
+    const headers = AxiosHeaders.from(axios.defaults.headers.common).toJSON();
 
     axios.post('/foo', 'fizz=buzz');
 
-    getAjaxRequest().then(function (request) {
+    return getAjaxRequest().then(function (request) {
       for (const key in headers) {
-        if (headers.hasOwnProperty(key)) {
-          expect(request.requestHeaders[key]).toEqual(headers[key]);
-        }
+         expect(request.requestHeaders[key]).toEqual(headers[key]);
       }
-      done();
     });
   });