From 5bfd2ea9f63e59efaef3f1a659b55bbb9778fce2 Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Thu, 1 Mar 2018 23:53:38 +0200
Subject: [PATCH 01/10] Fixing #385 - Keep defaults local to instance

---
 lib/axios.js                |  2 +-
 lib/core/Axios.js           | 14 +++++++----
 lib/utils.js                | 48 ++++++++++++++++++++++++++++++++++++-
 test/specs/defaults.spec.js |  4 ++--
 test/specs/options.spec.js  | 28 ++++++++++++++++++++++
 5 files changed, 87 insertions(+), 9 deletions(-)

diff --git a/lib/axios.js b/lib/axios.js
index ed1f519..68621dd 100644
--- a/lib/axios.js
+++ b/lib/axios.js
@@ -32,7 +32,7 @@ axios.Axios = Axios;
 
 // Factory for creating new instances
 axios.create = function create(instanceConfig) {
-  return createInstance(utils.merge(defaults, instanceConfig));
+  return createInstance(utils.mergeConfig(axios.defaults, instanceConfig || {}));
 };
 
 // Expose Cancel & CancelToken
diff --git a/lib/core/Axios.js b/lib/core/Axios.js
index f1af3e7..766a897 100644
--- a/lib/core/Axios.js
+++ b/lib/core/Axios.js
@@ -1,6 +1,5 @@
 'use strict';
 
-var defaults = require('./../defaults');
 var utils = require('./../utils');
 var InterceptorManager = require('./InterceptorManager');
 var dispatchRequest = require('./dispatchRequest');
@@ -24,15 +23,20 @@ function Axios(instanceConfig) {
  * @param {Object} config The config specific for this request (merged with this.defaults)
  */
 Axios.prototype.request = function request(config) {
+  config = config || {};
+
   /*eslint no-param-reassign:0*/
   // Allow for axios('example/url'[, config]) a la fetch API
   if (typeof config === 'string') {
-    config = utils.merge({
-      url: arguments[0]
-    }, arguments[1]);
+    config = arguments[1] || {};
+    config.url = arguments[0];
   }
 
-  config = utils.merge(defaults, this.defaults, { method: 'get' }, config);
+  if (!config.method) {
+    config.method = 'get';
+  }
+
+  config = utils.mergeConfig(this.defaults, config);
   config.method = config.method.toLowerCase();
 
   // Hook up interceptors middleware
diff --git a/lib/utils.js b/lib/utils.js
index b3fd865..342fa1f 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -279,6 +279,51 @@ function extend(a, b, thisArg) {
   return a;
 }
 
+function mergeConfig(defaults, instanceConfig) {
+  var config = {};
+  forEach(['url', 'method', 'params', 'data'], function(prop) {
+    config[prop] = instanceConfig[prop];
+  });
+  forEach(['headers', 'auth', 'proxy'], function(prop) {
+    if (!isUndefined(instanceConfig[prop])) {
+      if (!isObject(instanceConfig[prop])) {
+        config[prop] = instanceConfig[prop];
+      } else {
+        config[prop] = merge(
+          defaults[prop],
+          instanceConfig[prop]
+        );
+      }
+    } else if (!isUndefined(defaults[prop])) {
+      config[prop] = JSON.parse(JSON.stringify(defaults[prop]));
+    }
+  });
+  var remainingProperties = [
+    'baseURL',
+    'transformRequest',
+    'transformResponse',
+    'paramsSerializer',
+    'timeout',
+    'withCredentials',
+    'adapter',
+    'responseType',
+    'xsrfCookieName',
+    'xsrfHeaderName',
+    'onUploadProgress',
+    'onDownloadProgress',
+    'maxContentLength',
+    'validateStatus',
+    'maxRedirects',
+    'httpAgent',
+    'httpsAgent',
+    'cancelToken'
+  ];
+  forEach(remainingProperties, function(prop) {
+    config[prop] = !isUndefined(instanceConfig[prop]) ? instanceConfig[prop] : defaults[prop];
+  });
+  return config;
+}
+
 module.exports = {
   isArray: isArray,
   isArrayBuffer: isArrayBuffer,
@@ -299,5 +344,6 @@ module.exports = {
   forEach: forEach,
   merge: merge,
   extend: extend,
-  trim: trim
+  trim: trim,
+  mergeConfig: mergeConfig
 };
diff --git a/test/specs/defaults.spec.js b/test/specs/defaults.spec.js
index de19b6a..c8ee72e 100644
--- a/test/specs/defaults.spec.js
+++ b/test/specs/defaults.spec.js
@@ -148,14 +148,14 @@ describe('defaults', function () {
     });
   });
 
-  it('should be used by custom instance if set after instance created', function (done) {
+  it('should not be used by custom instance if set after instance created', function (done) {
     var instance = axios.create();
     axios.defaults.baseURL = 'http://example.org/';
 
     instance.get('/foo');
 
     getAjaxRequest().then(function (request) {
-      expect(request.url).toBe('http://example.org/foo');
+      expect(request.url).toBe('/foo');
       done();
     });
   });
diff --git a/test/specs/options.spec.js b/test/specs/options.spec.js
index 6520b8a..762b851 100644
--- a/test/specs/options.spec.js
+++ b/test/specs/options.spec.js
@@ -81,4 +81,32 @@ describe('options', function () {
       done();
     });
   });
+
+  it('should change only the baseURL of the specified instance', function() {
+    var instance1 = axios.create();
+    var instance2 = axios.create();
+
+    instance1.defaults.baseURL = 'http://instance1.example.com/';
+
+    expect(instance2.defaults.baseURL).not.toBe('http://instance1.example.com/');
+  });
+
+  it('should change only the headers of the specified instance', function() {
+    var instance1 = axios.create();
+    var instance2 = axios.create();
+
+    instance1.defaults.headers.common.Authorization = 'faketoken';
+    instance2.defaults.headers.common.Authorization = 'differentfaketoken';
+
+    instance1.defaults.headers.common['Content-Type'] = 'application/xml';
+    instance2.defaults.headers.common['Content-Type'] = 'application/x-www-form-urlencoded';
+
+    expect(axios.defaults.headers.common.Authorization).toBe(undefined);
+    expect(instance1.defaults.headers.common.Authorization).toBe('faketoken');
+    expect(instance2.defaults.headers.common.Authorization).toBe('differentfaketoken');
+
+    expect(axios.defaults.headers.common['Content-Type']).toBe(undefined);
+    expect(instance1.defaults.headers.common['Content-Type']).toBe('application/xml');
+    expect(instance2.defaults.headers.common['Content-Type']).toBe('application/x-www-form-urlencoded');
+  });
 });

From d78204712a88f9e7c8ebad728143dee56ca995f3 Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Fri, 9 Mar 2018 13:58:08 +0200
Subject: [PATCH 02/10] Clean up PR

---
 lib/axios.js      |  2 +-
 lib/core/Axios.js | 10 +++------
 lib/utils.js      | 52 ++++++++++++++++++++---------------------------
 3 files changed, 26 insertions(+), 38 deletions(-)

diff --git a/lib/axios.js b/lib/axios.js
index 68621dd..11e274c 100644
--- a/lib/axios.js
+++ b/lib/axios.js
@@ -32,7 +32,7 @@ axios.Axios = Axios;
 
 // Factory for creating new instances
 axios.create = function create(instanceConfig) {
-  return createInstance(utils.mergeConfig(axios.defaults, instanceConfig || {}));
+  return createInstance(utils.mergeConfig(axios.defaults, instanceConfig));
 };
 
 // Expose Cancel & CancelToken
diff --git a/lib/core/Axios.js b/lib/core/Axios.js
index 766a897..92865d3 100644
--- a/lib/core/Axios.js
+++ b/lib/core/Axios.js
@@ -23,21 +23,17 @@ function Axios(instanceConfig) {
  * @param {Object} config The config specific for this request (merged with this.defaults)
  */
 Axios.prototype.request = function request(config) {
-  config = config || {};
-
   /*eslint no-param-reassign:0*/
   // Allow for axios('example/url'[, config]) a la fetch API
   if (typeof config === 'string') {
     config = arguments[1] || {};
     config.url = arguments[0];
-  }
-
-  if (!config.method) {
-    config.method = 'get';
+  } else {
+    config = config || {};
   }
 
   config = utils.mergeConfig(this.defaults, config);
-  config.method = config.method.toLowerCase();
+  config.method = config.method ? config.method.toLowerCase() : 'get';
 
   // Hook up interceptors middleware
   var chain = [dispatchRequest, undefined];
diff --git a/lib/utils.js b/lib/utils.js
index 342fa1f..14225bd 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -279,47 +279,39 @@ function extend(a, b, thisArg) {
   return a;
 }
 
+
+/**
+ * Config-specific merge-function which creates a new config-object
+ * based on given defaults and instance config.
+ *
+ * @param {Object} defaults Defaults
+ * @param {Object} instanceConfig Instance-specific config
+ * @returns {Object} New object resulting from merging instanceConfig to defaults
+ */
 function mergeConfig(defaults, instanceConfig) {
+  instanceConfig = instanceConfig || {};
   var config = {};
-  forEach(['url', 'method', 'params', 'data'], function(prop) {
+  forEach(['url', 'method', 'params', 'data'], function valueFromInstanceConfig(prop) {
     config[prop] = instanceConfig[prop];
   });
-  forEach(['headers', 'auth', 'proxy'], function(prop) {
+  forEach(['headers', 'auth', 'proxy'], function mergeInstanceConfigWithDefaults(prop) {
     if (!isUndefined(instanceConfig[prop])) {
-      if (!isObject(instanceConfig[prop])) {
-        config[prop] = instanceConfig[prop];
+      if (isObject(instanceConfig[prop])) {
+        config[prop] = merge(defaults[prop], instanceConfig[prop]);
       } else {
-        config[prop] = merge(
-          defaults[prop],
-          instanceConfig[prop]
-        );
+        config[prop] = instanceConfig[prop];
       }
     } else if (!isUndefined(defaults[prop])) {
       config[prop] = JSON.parse(JSON.stringify(defaults[prop]));
     }
   });
-  var remainingProperties = [
-    'baseURL',
-    'transformRequest',
-    'transformResponse',
-    'paramsSerializer',
-    'timeout',
-    'withCredentials',
-    'adapter',
-    'responseType',
-    'xsrfCookieName',
-    'xsrfHeaderName',
-    'onUploadProgress',
-    'onDownloadProgress',
-    'maxContentLength',
-    'validateStatus',
-    'maxRedirects',
-    'httpAgent',
-    'httpsAgent',
-    'cancelToken'
-  ];
-  forEach(remainingProperties, function(prop) {
-    config[prop] = !isUndefined(instanceConfig[prop]) ? instanceConfig[prop] : defaults[prop];
+  forEach([
+    'baseURL', 'transformRequest', 'transformResponse', 'paramsSerializer',
+    'timeout', 'withCredentials', 'adapter', 'responseType', 'xsrfCookieName',
+    'xsrfHeaderName', 'onUploadProgress', 'onDownloadProgress', 'maxContentLength',
+    'validateStatus', 'maxRedirects', 'httpAgent', 'httpsAgent', 'cancelToken'
+  ], function defaultToInstanceConfig(prop) {
+    config[prop] = isUndefined(instanceConfig[prop]) ? defaults[prop] : instanceConfig[prop];
   });
   return config;
 }

From 72c66dfdecbcc165c52fcd19d1f8444ad8c011c6 Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Fri, 23 Mar 2018 20:21:02 +0100
Subject: [PATCH 03/10] Refactor and introduce deepMerge

---
 lib/axios.js            |  3 +-
 lib/core/Axios.js       |  3 +-
 lib/core/mergeConfig.js | 44 +++++++++++++++++++++++++++
 lib/utils.js            | 67 +++++++++++++++++------------------------
 4 files changed, 76 insertions(+), 41 deletions(-)
 create mode 100644 lib/core/mergeConfig.js

diff --git a/lib/axios.js b/lib/axios.js
index 11e274c..8142437 100644
--- a/lib/axios.js
+++ b/lib/axios.js
@@ -3,6 +3,7 @@
 var utils = require('./utils');
 var bind = require('./helpers/bind');
 var Axios = require('./core/Axios');
+var mergeConfig = require('./core/mergeConfig');
 var defaults = require('./defaults');
 
 /**
@@ -32,7 +33,7 @@ axios.Axios = Axios;
 
 // Factory for creating new instances
 axios.create = function create(instanceConfig) {
-  return createInstance(utils.mergeConfig(axios.defaults, instanceConfig));
+  return createInstance(mergeConfig(axios.defaults, instanceConfig));
 };
 
 // Expose Cancel & CancelToken
diff --git a/lib/core/Axios.js b/lib/core/Axios.js
index 92865d3..8407a96 100644
--- a/lib/core/Axios.js
+++ b/lib/core/Axios.js
@@ -3,6 +3,7 @@
 var utils = require('./../utils');
 var InterceptorManager = require('./InterceptorManager');
 var dispatchRequest = require('./dispatchRequest');
+var mergeConfig = require('./mergeConfig');
 
 /**
  * Create a new instance of Axios
@@ -32,7 +33,7 @@ Axios.prototype.request = function request(config) {
     config = config || {};
   }
 
-  config = utils.mergeConfig(this.defaults, config);
+  config = mergeConfig(this.defaults, config);
   config.method = config.method ? config.method.toLowerCase() : 'get';
 
   // Hook up interceptors middleware
diff --git a/lib/core/mergeConfig.js b/lib/core/mergeConfig.js
new file mode 100644
index 0000000..fea1238
--- /dev/null
+++ b/lib/core/mergeConfig.js
@@ -0,0 +1,44 @@
+'use strict';
+
+var utils = require('../utils');
+
+/**
+ * Config-specific merge-function which creates a new config-object
+ * based on given defaults and instance config.
+ *
+ * @param {Object} defaults Defaults
+ * @param {Object} instanceConfig Instance-specific config
+ * @returns {Object} New object resulting from merging instanceConfig to defaults
+ */
+module.exports = function mergeConfig(defaults, instanceConfig) {
+  // eslint-disable-next-line no-param-reassign
+  instanceConfig = instanceConfig || {};
+  var config = {};
+
+  utils.forEach(['url', 'method', 'params', 'data'], function valueFromInstanceConfig(prop) {
+    config[prop] = instanceConfig[prop];
+  });
+
+  utils.forEach(['headers', 'auth', 'proxy'], function mergeInstanceConfigWithDefaults(prop) {
+    if (typeof instanceConfig[prop] !== 'undefined') {
+      if (typeof instanceConfig[prop] === 'object') {
+        config[prop] = utils.deepMerge(defaults[prop], instanceConfig[prop]);
+      } else {
+        config[prop] = instanceConfig[prop];
+      }
+    } else if (typeof defaults[prop] !== 'undefined') {
+      config[prop] = utils.deepMerge(defaults[prop]);
+    }
+  });
+
+  utils.forEach([
+    'baseURL', 'transformRequest', 'transformResponse', 'paramsSerializer',
+    'timeout', 'withCredentials', 'adapter', 'responseType', 'xsrfCookieName',
+    'xsrfHeaderName', 'onUploadProgress', 'onDownloadProgress', 'maxContentLength',
+    'validateStatus', 'maxRedirects', 'httpAgent', 'httpsAgent', 'cancelToken'
+  ], function defaultToInstanceConfig(prop) {
+    config[prop] = typeof instanceConfig[prop] === 'undefined' ? defaults[prop] : instanceConfig[prop];
+  });
+
+  return config;
+};
diff --git a/lib/utils.js b/lib/utils.js
index 14225bd..856aba3 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -260,6 +260,32 @@ function merge(/* obj1, obj2, obj3, ... */) {
   return result;
 }
 
+/**
+ * Function equal to merge with the difference being that no reference
+ * to original objects is kept.
+ *
+ * @see merge
+ * @param {Object} obj1 Object to merge
+ * @returns {Object} Result of all merge properties
+ */
+function deepMerge(/* obj1, obj2, obj3, ... */) {
+  var result = {};
+  function assignValue(val, key) {
+    if (typeof result[key] === 'object' && typeof val === 'object') {
+      result[key] = merge(result[key], val);
+    } else if (typeof val === 'object') {
+      result[key] = merge({}, val);
+    } else {
+      result[key] = val;
+    }
+  }
+
+  for (var i = 0, l = arguments.length; i < l; i++) {
+    forEach(arguments[i], assignValue);
+  }
+  return result;
+}
+
 /**
  * Extends object a by mutably adding to it the properties of object b.
  *
@@ -279,43 +305,6 @@ function extend(a, b, thisArg) {
   return a;
 }
 
-
-/**
- * Config-specific merge-function which creates a new config-object
- * based on given defaults and instance config.
- *
- * @param {Object} defaults Defaults
- * @param {Object} instanceConfig Instance-specific config
- * @returns {Object} New object resulting from merging instanceConfig to defaults
- */
-function mergeConfig(defaults, instanceConfig) {
-  instanceConfig = instanceConfig || {};
-  var config = {};
-  forEach(['url', 'method', 'params', 'data'], function valueFromInstanceConfig(prop) {
-    config[prop] = instanceConfig[prop];
-  });
-  forEach(['headers', 'auth', 'proxy'], function mergeInstanceConfigWithDefaults(prop) {
-    if (!isUndefined(instanceConfig[prop])) {
-      if (isObject(instanceConfig[prop])) {
-        config[prop] = merge(defaults[prop], instanceConfig[prop]);
-      } else {
-        config[prop] = instanceConfig[prop];
-      }
-    } else if (!isUndefined(defaults[prop])) {
-      config[prop] = JSON.parse(JSON.stringify(defaults[prop]));
-    }
-  });
-  forEach([
-    'baseURL', 'transformRequest', 'transformResponse', 'paramsSerializer',
-    'timeout', 'withCredentials', 'adapter', 'responseType', 'xsrfCookieName',
-    'xsrfHeaderName', 'onUploadProgress', 'onDownloadProgress', 'maxContentLength',
-    'validateStatus', 'maxRedirects', 'httpAgent', 'httpsAgent', 'cancelToken'
-  ], function defaultToInstanceConfig(prop) {
-    config[prop] = isUndefined(instanceConfig[prop]) ? defaults[prop] : instanceConfig[prop];
-  });
-  return config;
-}
-
 module.exports = {
   isArray: isArray,
   isArrayBuffer: isArrayBuffer,
@@ -335,7 +324,7 @@ module.exports = {
   isStandardBrowserEnv: isStandardBrowserEnv,
   forEach: forEach,
   merge: merge,
+  deepMerge: deepMerge,
   extend: extend,
-  trim: trim,
-  mergeConfig: mergeConfig
+  trim: trim
 };

From 82030ae054ba10bbd25ef00b304990632780f11d Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Tue, 3 Apr 2018 21:53:17 +0200
Subject: [PATCH 04/10] Use deepMerge in deepMerge

---
 lib/utils.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/utils.js b/lib/utils.js
index 856aba3..aca5f4e 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -272,9 +272,9 @@ function deepMerge(/* obj1, obj2, obj3, ... */) {
   var result = {};
   function assignValue(val, key) {
     if (typeof result[key] === 'object' && typeof val === 'object') {
-      result[key] = merge(result[key], val);
+      result[key] = deepMerge(result[key], val);
     } else if (typeof val === 'object') {
-      result[key] = merge({}, val);
+      result[key] = deepMerge({}, val);
     } else {
       result[key] = val;
     }

From 6083d639c54cb093862bfee3f55d45e6456aa217 Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Tue, 3 Apr 2018 21:53:45 +0200
Subject: [PATCH 05/10] Rename mergeConfig arguments

---
 lib/core/mergeConfig.js | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/lib/core/mergeConfig.js b/lib/core/mergeConfig.js
index fea1238..3b3d610 100644
--- a/lib/core/mergeConfig.js
+++ b/lib/core/mergeConfig.js
@@ -6,28 +6,28 @@ var utils = require('../utils');
  * Config-specific merge-function which creates a new config-object
  * based on given defaults and instance config.
  *
- * @param {Object} defaults Defaults
- * @param {Object} instanceConfig Instance-specific config
- * @returns {Object} New object resulting from merging instanceConfig to defaults
+ * @param {Object} config1
+ * @param {Object} config2
+ * @returns {Object} New object resulting from merging config2 to config1
  */
-module.exports = function mergeConfig(defaults, instanceConfig) {
+module.exports = function mergeConfig(config1, config2) {
   // eslint-disable-next-line no-param-reassign
-  instanceConfig = instanceConfig || {};
+  config2 = config2 || {};
   var config = {};
 
   utils.forEach(['url', 'method', 'params', 'data'], function valueFromInstanceConfig(prop) {
-    config[prop] = instanceConfig[prop];
+    config[prop] = config2[prop];
   });
 
   utils.forEach(['headers', 'auth', 'proxy'], function mergeInstanceConfigWithDefaults(prop) {
-    if (typeof instanceConfig[prop] !== 'undefined') {
-      if (typeof instanceConfig[prop] === 'object') {
-        config[prop] = utils.deepMerge(defaults[prop], instanceConfig[prop]);
+    if (typeof config2[prop] !== 'undefined') {
+      if (typeof config2[prop] === 'object') {
+        config[prop] = utils.deepMerge(config1[prop], config2[prop]);
       } else {
-        config[prop] = instanceConfig[prop];
+        config[prop] = config2[prop];
       }
-    } else if (typeof defaults[prop] !== 'undefined') {
-      config[prop] = utils.deepMerge(defaults[prop]);
+    } else if (typeof config1[prop] !== 'undefined') {
+      config[prop] = utils.deepMerge(config1[prop]);
     }
   });
 
@@ -37,7 +37,7 @@ module.exports = function mergeConfig(defaults, instanceConfig) {
     'xsrfHeaderName', 'onUploadProgress', 'onDownloadProgress', 'maxContentLength',
     'validateStatus', 'maxRedirects', 'httpAgent', 'httpsAgent', 'cancelToken'
   ], function defaultToInstanceConfig(prop) {
-    config[prop] = typeof instanceConfig[prop] === 'undefined' ? defaults[prop] : instanceConfig[prop];
+    config[prop] = typeof config2[prop] === 'undefined' ? config1[prop] : config2[prop];
   });
 
   return config;

From 506d4e894157cd5b94432c4d7904d832cf0b951f Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Tue, 3 Apr 2018 22:19:38 +0200
Subject: [PATCH 06/10] Unit tests for deepMerge

---
 test/specs/utils/deepMerge.spec.js | 66 ++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 test/specs/utils/deepMerge.spec.js

diff --git a/test/specs/utils/deepMerge.spec.js b/test/specs/utils/deepMerge.spec.js
new file mode 100644
index 0000000..d879593
--- /dev/null
+++ b/test/specs/utils/deepMerge.spec.js
@@ -0,0 +1,66 @@
+var deepMerge = require('../../../lib/utils').deepMerge;
+
+describe('utils::deepMerge', function () {
+  it('should be immutable', function () {
+    var a = {};
+    var b = {foo: 123};
+    var c = {bar: 456};
+
+    deepMerge(a, b, c);
+
+    expect(typeof a.foo).toEqual('undefined');
+    expect(typeof a.bar).toEqual('undefined');
+    expect(typeof b.bar).toEqual('undefined');
+    expect(typeof c.foo).toEqual('undefined');
+  });
+
+  it('should deepMerge properties', function () {
+    var a = {foo: 123};
+    var b = {bar: 456};
+    var c = {foo: 789};
+    var d = deepMerge(a, b, c);
+
+    expect(d.foo).toEqual(789);
+    expect(d.bar).toEqual(456);
+  });
+
+  it('should deepMerge recursively', function () {
+    var a = {foo: {bar: 123}};
+    var b = {foo: {baz: 456}, bar: {qux: 789}};
+
+    expect(deepMerge(a, b)).toEqual({
+      foo: {
+        bar: 123,
+        baz: 456
+      },
+      bar: {
+        qux: 789
+      }
+    });
+  });
+
+  it('should remove all references from nested objects', function () {
+    var a = {foo: {bar: 123}};
+    var b = {};
+    var d = deepMerge(a, b);
+
+    expect(d).toEqual({
+      foo: {
+        bar: 123
+      }
+    });
+
+    expect(d.foo).not.toBe(a.foo);
+  });
+
+  it('handles null and undefined arguments', function () {
+    expect(deepMerge(undefined, undefined)).toEqual({});
+    expect(deepMerge(undefined, {foo: 123})).toEqual({foo: 123});
+    expect(deepMerge({foo: 123}, undefined)).toEqual({foo: 123});
+
+    expect(deepMerge(null, null)).toEqual({});
+    expect(deepMerge(null, {foo: 123})).toEqual({foo: 123});
+    expect(deepMerge({foo: 123}, null)).toEqual({foo: 123});
+  });
+});
+

From b1c378606f09a38d7e6713595add07676882b8f2 Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Tue, 3 Apr 2018 22:29:15 +0200
Subject: [PATCH 07/10] Prevent undefined values in mergeConfig

---
 lib/core/mergeConfig.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/core/mergeConfig.js b/lib/core/mergeConfig.js
index 3b3d610..e8782ab 100644
--- a/lib/core/mergeConfig.js
+++ b/lib/core/mergeConfig.js
@@ -16,7 +16,9 @@ module.exports = function mergeConfig(config1, config2) {
   var config = {};
 
   utils.forEach(['url', 'method', 'params', 'data'], function valueFromInstanceConfig(prop) {
-    config[prop] = config2[prop];
+    if (typeof config2[prop] !== 'undefined') {
+      config[prop] = config2[prop];
+    }
   });
 
   utils.forEach(['headers', 'auth', 'proxy'], function mergeInstanceConfigWithDefaults(prop) {

From ff61caacb78da139b3a1b199df2c4b40cd55a3cc Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Sat, 7 Apr 2018 13:40:21 +0200
Subject: [PATCH 08/10] Slight refactor/namings/comment on mergeConfig

---
 lib/core/mergeConfig.js | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/lib/core/mergeConfig.js b/lib/core/mergeConfig.js
index e8782ab..ad7d0f8 100644
--- a/lib/core/mergeConfig.js
+++ b/lib/core/mergeConfig.js
@@ -4,7 +4,7 @@ var utils = require('../utils');
 
 /**
  * Config-specific merge-function which creates a new config-object
- * based on given defaults and instance config.
+ * by merging two configuration objects together.
  *
  * @param {Object} config1
  * @param {Object} config2
@@ -15,13 +15,11 @@ module.exports = function mergeConfig(config1, config2) {
   config2 = config2 || {};
   var config = {};
 
-  utils.forEach(['url', 'method', 'params', 'data'], function valueFromInstanceConfig(prop) {
-    if (typeof config2[prop] !== 'undefined') {
-      config[prop] = config2[prop];
-    }
+  utils.forEach(['url', 'method', 'params', 'data'], function valueFromConfig2(prop) {
+    config[prop] = config2[prop];
   });
 
-  utils.forEach(['headers', 'auth', 'proxy'], function mergeInstanceConfigWithDefaults(prop) {
+  utils.forEach(['headers', 'auth', 'proxy'], function mergeValues(prop) {
     if (typeof config2[prop] !== 'undefined') {
       if (typeof config2[prop] === 'object') {
         config[prop] = utils.deepMerge(config1[prop], config2[prop]);
@@ -38,7 +36,7 @@ module.exports = function mergeConfig(config1, config2) {
     'timeout', 'withCredentials', 'adapter', 'responseType', 'xsrfCookieName',
     'xsrfHeaderName', 'onUploadProgress', 'onDownloadProgress', 'maxContentLength',
     'validateStatus', 'maxRedirects', 'httpAgent', 'httpsAgent', 'cancelToken'
-  ], function defaultToInstanceConfig(prop) {
+  ], function defaultToConfig2(prop) {
     config[prop] = typeof config2[prop] === 'undefined' ? config1[prop] : config2[prop];
   });
 

From 143bbbe1b96f7819d6df5f1c249ba0964cf84819 Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Sat, 7 Apr 2018 15:54:56 +0200
Subject: [PATCH 09/10] Spec for mergeConfig, finalize logic

---
 lib/core/mergeConfig.js             | 26 ++++++-----
 lib/defaults.js                     |  1 -
 test/specs/core/mergeConfig.spec.js | 69 +++++++++++++++++++++++++++++
 3 files changed, 85 insertions(+), 11 deletions(-)
 create mode 100644 test/specs/core/mergeConfig.spec.js

diff --git a/lib/core/mergeConfig.js b/lib/core/mergeConfig.js
index ad7d0f8..1da9040 100644
--- a/lib/core/mergeConfig.js
+++ b/lib/core/mergeConfig.js
@@ -16,18 +16,20 @@ module.exports = function mergeConfig(config1, config2) {
   var config = {};
 
   utils.forEach(['url', 'method', 'params', 'data'], function valueFromConfig2(prop) {
-    config[prop] = config2[prop];
+    if (typeof config2[prop] !== 'undefined') {
+      config[prop] = config2[prop];
+    }
   });
 
-  utils.forEach(['headers', 'auth', 'proxy'], function mergeValues(prop) {
-    if (typeof config2[prop] !== 'undefined') {
-      if (typeof config2[prop] === 'object') {
-        config[prop] = utils.deepMerge(config1[prop], config2[prop]);
-      } else {
-        config[prop] = config2[prop];
-      }
-    } else if (typeof config1[prop] !== 'undefined') {
+  utils.forEach(['headers', 'auth', 'proxy'], function mergeDeepProperties(prop) {
+    if (utils.isObject(config2[prop])) {
+      config[prop] = utils.deepMerge(config1[prop], config2[prop]);
+    } else if (typeof config2[prop] !== 'undefined') {
+      config[prop] = config2[prop];
+    } else if (utils.isObject(config1[prop])) {
       config[prop] = utils.deepMerge(config1[prop]);
+    } else if (typeof config1[prop] !== 'undefined') {
+      config[prop] = config1[prop];
     }
   });
 
@@ -37,7 +39,11 @@ module.exports = function mergeConfig(config1, config2) {
     'xsrfHeaderName', 'onUploadProgress', 'onDownloadProgress', 'maxContentLength',
     'validateStatus', 'maxRedirects', 'httpAgent', 'httpsAgent', 'cancelToken'
   ], function defaultToConfig2(prop) {
-    config[prop] = typeof config2[prop] === 'undefined' ? config1[prop] : config2[prop];
+    if (typeof config2[prop] !== 'undefined') {
+      config[prop] = config2[prop];
+    } else if (typeof config1[prop] !== 'undefined') {
+      config[prop] = config1[prop];
+    }
   });
 
   return config;
diff --git a/lib/defaults.js b/lib/defaults.js
index e1bc1ca..65a25d5 100644
--- a/lib/defaults.js
+++ b/lib/defaults.js
@@ -26,7 +26,6 @@ function getDefaultAdapter() {
 }
 
 var defaults = {
-  method: 'get',
   adapter: getDefaultAdapter(),
 
   transformRequest: [function transformRequest(data, headers) {
diff --git a/test/specs/core/mergeConfig.spec.js b/test/specs/core/mergeConfig.spec.js
new file mode 100644
index 0000000..bf6d209
--- /dev/null
+++ b/test/specs/core/mergeConfig.spec.js
@@ -0,0 +1,69 @@
+var defaults = require('../../../lib/defaults');
+var mergeConfig = require('../../../lib/core/mergeConfig');
+
+describe('core::mergeConfig', function() {
+  it('should accept undefined for second argument', function() {
+    expect(mergeConfig(defaults, undefined)).toEqual(defaults);
+  });
+
+  it('should accept an object for second argument', function() {
+    expect(mergeConfig(defaults, {})).toEqual(defaults);
+  });
+
+  it('should not leave references', function() {
+    var merged = mergeConfig(defaults, {});
+    expect(merged).not.toBe(defaults);
+    expect(merged.headers).not.toBe(defaults.headers);
+  });
+
+  it('should allow setting request options', function() {
+    var config = {
+      url: '__sample url__',
+      method: '__sample method__',
+      params: '__sample params__',
+      data: { foo: true }
+    };
+    var merged = mergeConfig(defaults, config);
+    expect(merged.url).toEqual(config.url);
+    expect(merged.method).toEqual(config.method);
+    expect(merged.params).toEqual(config.params);
+    expect(merged.data).toEqual(config.data);
+  });
+
+  it('should not inherit request options', function() {
+    var localDefaults = {
+      url: '__sample url__',
+      method: '__sample method__',
+      params: '__sample params__',
+      data: { foo: true }
+    };
+    var merged = mergeConfig(localDefaults, {});
+    expect(merged.url).toEqual(undefined);
+    expect(merged.method).toEqual(undefined);
+    expect(merged.params).toEqual(undefined);
+    expect(merged.data).toEqual(undefined);
+  });
+
+  it('should merge auth, headers, proxy with defaults', function() {
+    expect(mergeConfig({ auth: undefined }, { auth: { user: 'foo', pass: 'test' } })).toEqual({
+      auth: { user: 'foo', pass: 'test' }
+    });
+    expect(mergeConfig({ auth: { user: 'foo', pass: 'test' } }, { auth: { pass: 'foobar' } })).toEqual({
+      auth: { user: 'foo', pass: 'foobar' }
+    });
+  });
+
+  it('should overwrite auth, headers, proxy with a non-object value', function() {
+    expect(mergeConfig({ auth: { user: 'foo', pass: 'test' } }, { auth: false })).toEqual({
+      auth: false
+    });
+    expect(mergeConfig({ auth: { user: 'foo', pass: 'test' } }, { auth: null })).toEqual({
+      auth: null
+    });
+  });
+
+  it('should allow setting other options', function() {
+    var merged = mergeConfig(defaults, { timeout: 123 });
+    expect(merged.timeout).toEqual(123);
+  });
+});

From 4e8039ef65d3daa35b1c5a1cd13beaf4c283249a Mon Sep 17 00:00:00 2001
From: Martti Laine <martti@codeclown.net>
Date: Tue, 10 Apr 2018 22:29:02 +0200
Subject: [PATCH 10/10] Remember socketPath in mergeConfig

---
 lib/core/mergeConfig.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/core/mergeConfig.js b/lib/core/mergeConfig.js
index 1da9040..6097a3e 100644
--- a/lib/core/mergeConfig.js
+++ b/lib/core/mergeConfig.js
@@ -37,7 +37,8 @@ module.exports = function mergeConfig(config1, config2) {
     'baseURL', 'transformRequest', 'transformResponse', 'paramsSerializer',
     'timeout', 'withCredentials', 'adapter', 'responseType', 'xsrfCookieName',
     'xsrfHeaderName', 'onUploadProgress', 'onDownloadProgress', 'maxContentLength',
-    'validateStatus', 'maxRedirects', 'httpAgent', 'httpsAgent', 'cancelToken'
+    'validateStatus', 'maxRedirects', 'httpAgent', 'httpsAgent', 'cancelToken',
+    'socketPath'
   ], function defaultToConfig2(prop) {
     if (typeof config2[prop] !== 'undefined') {
       config[prop] = config2[prop];