Bug/allow header to contain http verb keys #1252 (#1258)

* Failing test for #1252

* Only delete header keys that match an HTTP verb if the value is a non-string

Co-authored-by: David Ko <david.ko@pvtmethod.com>
Co-authored-by: Jay <jasonsaayman@gmail.com>

lib/core/dispatchRequest.js

@@ -43,7 +43,9 @@ module.exports = function dispatchRequest(config) {
   utils.forEach(
     ['delete', 'get', 'head', 'post', 'put', 'patch', 'common'],
     function cleanHeaderConfig(method) {
-      delete config.headers[method];
+      if (typeof config.headers[method] !== 'string') {
+        delete config.headers[method];
+      }
     }
   );
 

test/specs/headers.spec.js

@@ -86,4 +86,17 @@ describe('headers', function () {
       done();
     });
   });
+
+  describe('when a header key matches an HTTP verb', function() {
+    it('preserves the header value', function(done) {
+      axios.post('/foo', null, { 'headers': { 'delete': 'test' } });
+
+      getAjaxRequest().then(function (request) {
+        var headerValue = request.requestHeaders['delete'];
+
+        expect(headerValue).toEqual('test');
+        done();
+      });
+    });
+  });
 });