fix: added a option to choose between legacy and the new request/response interceptor ordering

* test: add request interceptor tests for legacy and ordered execution

* feat: add legacy interceptor request/response ordering option

---------

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

README.md

@@ -615,6 +615,9 @@ These are the available config options for making requests. Only the `url` is re
 
     // throw ETIMEDOUT error instead of generic ECONNABORTED on request timeouts
     clarifyTimeoutError: false,
+
+    // use the legacy interceptor request/response ordering
+    legacyInterceptorReqResOrdering: true, // default
   },
 
   env: {

index.d.cts

@@ -302,6 +302,7 @@ declare namespace axios {
     silentJSONParsing?: boolean;
     forcedJSONParsing?: boolean;
     clarifyTimeoutError?: boolean;
+    legacyInterceptorReqResOrdering?: boolean;
   }
 
   interface GenericAbortSignal {

index.d.ts

@@ -332,6 +332,7 @@ export interface TransitionalOptions {
   silentJSONParsing?: boolean;
   forcedJSONParsing?: boolean;
   clarifyTimeoutError?: boolean;
+  legacyInterceptorReqResOrdering?: boolean;
 }
 
 export interface GenericAbortSignal {

lib/core/Axios.js

@@ -8,6 +8,7 @@ import mergeConfig from './mergeConfig.js';
 import buildFullPath from './buildFullPath.js';
 import validator from '../helpers/validator.js';
 import AxiosHeaders from './AxiosHeaders.js';
+import transitionalDefaults from '../defaults/transitional.js';
 
 const validators = validator.validators;
 
@@ -80,7 +81,8 @@ class Axios {
       validator.assertOptions(transitional, {
         silentJSONParsing: validators.transitional(validators.boolean),
         forcedJSONParsing: validators.transitional(validators.boolean),
-        clarifyTimeoutError: validators.transitional(validators.boolean)
+        clarifyTimeoutError: validators.transitional(validators.boolean),
+        legacyInterceptorReqResOrdering: validators.transitional(validators.boolean)
       }, false);
     }
 
@@ -139,7 +141,14 @@ class Axios {
 
       synchronousRequestInterceptors = synchronousRequestInterceptors && interceptor.synchronous;
 
+      const transitional = config.transitional || transitionalDefaults;
+      const legacyInterceptorReqResOrdering = transitional && transitional.legacyInterceptorReqResOrdering;
+
+      if (legacyInterceptorReqResOrdering) {
         requestInterceptorChain.unshift(interceptor.fulfilled, interceptor.rejected);
+      } else {
+        requestInterceptorChain.push(interceptor.fulfilled, interceptor.rejected);
+      }
     });
 
     const responseInterceptorChain = [];

lib/defaults/transitional.js

@@ -3,5 +3,6 @@
 export default {
   silentJSONParsing: true,
   forcedJSONParsing: true,
-  clarifyTimeoutError: false
+  clarifyTimeoutError: false,
+  legacyInterceptorReqResOrdering: true
 };

test/specs/interceptors.spec.js

@@ -91,6 +91,63 @@ describe('interceptors', function () {
     });
   });
 
+  it('should execute request interceptor in legacy order', function (done) {
+    let sequence = '';
+    axios.interceptors.request.use(function (config) {
+      sequence += '1';
+      return config;
+    });
+
+    axios.interceptors.request.use(function (config) {
+      sequence += '2';
+      return config;
+    });
+
+    axios.interceptors.request.use(function (config) {
+      sequence += '3';
+      return config;
+    });
+
+    axios({
+      url: '/foo',
+    });
+
+    getAjaxRequest().then(function (request) {
+      expect(sequence).toBe('321');
+      done();
+    });
+  });
+
+    it('should execute request interceptor in order', function (done) {
+    let sequence = '';
+    axios.interceptors.request.use(function (config) {
+      sequence += '1';
+      return config;
+    });
+
+    axios.interceptors.request.use(function (config) {
+      sequence += '2';
+      return config;
+    });
+
+    axios.interceptors.request.use(function (config) {
+      sequence += '3';
+      return config;
+    });
+
+    axios({
+      url: '/foo',
+      transitional: {
+        legacyInterceptorReqResOrdering: false
+      }
+    });
+
+    getAjaxRequest().then(function (request) {
+      expect(sequence).toBe('123');
+      done();
+    });
+  });
+
   it('runs the interceptor if runWhen function is provided and resolves to true', function (done) {
     function onGetCall(config) {
       return config.method === 'get';