Fixing response with utf-8 BOM can not parse to json (#2419)

* fix: remove byte order marker (UTF-8 BOM) when transform response

* fix: remove BOM only utf-8

* test: utf-8 BOM

* fix: incorrect param name

Co-authored-by: Jay <jasonsaayman@gmail.com>

lib/adapters/http.js

@@ -235,6 +235,9 @@ module.exports = function httpAdapter(config) {
           var responseData = Buffer.concat(responseBuffer);
           if (config.responseType !== 'arraybuffer') {
             responseData = responseData.toString(config.responseEncoding);
+            if (!config.responseEncoding || config.responseEncoding === 'utf8') {
+              responseData = utils.stripBOM(responseData);
+            }
           }
 
           response.data = responseData;

lib/utils.js

@@ -312,6 +312,19 @@ function extend(a, b, thisArg) {
   return a;
 }
 
+/**
+ * Remove byte order marker. This catches EF BB BF (the UTF-8 BOM)
+ *
+ * @param {string} content with BOM
+ * @return {string} content value without BOM
+ */
+function stripBOM(content) {
+  if (content.charCodeAt(0) === 0xFEFF) {
+    content = content.slice(1);
+  }
+  return content;
+}
+
 module.exports = {
   isArray: isArray,
   isArrayBuffer: isArrayBuffer,
@@ -333,5 +346,6 @@ module.exports = {
   forEach: forEach,
   merge: merge,
   extend: extend,
-  trim: trim
+  trim: trim,
+  stripBOM: stripBOM
 };

test/unit/adapters/http.js

@@ -74,6 +74,26 @@ describe('supports http with nodejs', function () {
     });
   });
 
+  it('should allow passing JSON with BOM', function (done) {
+    var data = {
+      firstName: 'Fred',
+      lastName: 'Flintstone',
+      emailAddr: 'fred@example.com'
+    };
+
+    server = http.createServer(function (req, res) {
+      res.setHeader('Content-Type', 'application/json;charset=utf-8');
+      var bomBuffer = Buffer.from([0xEF, 0xBB, 0xBF])
+      var jsonBuffer = Buffer.from(JSON.stringify(data));
+      res.end(Buffer.concat([bomBuffer, jsonBuffer]));
+    }).listen(4444, function () {
+      axios.get('http://localhost:4444/').then(function (res) {
+        assert.deepEqual(res.data, data);
+        done();
+      });
+    });
+  });
+
   it('should redirect', function (done) {
     var str = 'test response';