issue#2609 | Sasha | predictable axios requests (#2702)

* issue#2609 | Sasha | predictable axios requests

- axios requests are not delayed by pre-emptive promise creation by default
- add options to interceptors api ("synchronous" and "runWhen")
- add documentation and unit tests

* issue#2609 | Sasha | pull request feedback changes

* issue#2609 | Sasha | additional feedback changes

* issue#2609 | Sasha | put back try/catch

* issue#2609 | Sasha | add 2 adapter unit tests

- remove check for requestCancelled

Co-authored-by: ak71845 <alexandre.korotkov@kroger.com>
Co-authored-by: Xianming Zhong <chinesedfan@qq.com>
Co-authored-by: Jay <jasonsaayman@gmail.com>

lib/core/Axios.js

@@ -45,20 +45,61 @@ Axios.prototype.request = function request(config) {
     config.method = 'get';
   }
 
-  // Hook up interceptors middleware
-  var chain = [dispatchRequest, undefined];
-  var promise = Promise.resolve(config);
-
+  // filter out skipped interceptors
+  var requestInterceptorChain = [];
+  var synchronousRequestInterceptors = true;
   this.interceptors.request.forEach(function unshiftRequestInterceptors(interceptor) {
-    chain.unshift(interceptor.fulfilled, interceptor.rejected);
+    if (typeof interceptor.runWhen === 'function' && interceptor.runWhen(config) === false) {
+      return;
+    }
+
+    synchronousRequestInterceptors = synchronousRequestInterceptors && interceptor.synchronous;
+
+    requestInterceptorChain.unshift(interceptor.fulfilled, interceptor.rejected);
   });
 
+  var responseInterceptorChain = [];
   this.interceptors.response.forEach(function pushResponseInterceptors(interceptor) {
-    chain.push(interceptor.fulfilled, interceptor.rejected);
+    responseInterceptorChain.push(interceptor.fulfilled, interceptor.rejected);
   });
 
-  while (chain.length) {
-    promise = promise.then(chain.shift(), chain.shift());
+  var promise;
+
+  if (!synchronousRequestInterceptors) {
+    var chain = [dispatchRequest, undefined];
+
+    Array.prototype.unshift.apply(chain, requestInterceptorChain);
+    chain.concat(responseInterceptorChain);
+
+    promise = Promise.resolve(config);
+    while (chain.length) {
+      promise = promise.then(chain.shift(), chain.shift());
+    }
+
+    return promise;
+  }
+
+
+  var newConfig = config;
+  while (requestInterceptorChain.length) {
+    var onFulfilled = requestInterceptorChain.shift();
+    var onRejected = requestInterceptorChain.shift();
+    try {
+      newConfig = onFulfilled(newConfig);
+    } catch (error) {
+      onRejected(error);
+      break;
+    }
+  }
+
+  try {
+    promise = dispatchRequest(newConfig);
+  } catch (error) {
+    return Promise.reject(error);
+  }
+
+  while (responseInterceptorChain.length) {
+    promise = promise.then(responseInterceptorChain.shift(), responseInterceptorChain.shift());
   }
 
   return promise;

lib/core/InterceptorManager.js

@@ -14,10 +14,12 @@ function InterceptorManager() {
  *
  * @return {Number} An ID used to remove interceptor later
  */
-InterceptorManager.prototype.use = function use(fulfilled, rejected) {
+InterceptorManager.prototype.use = function use(fulfilled, rejected, options) {
   this.handlers.push({
     fulfilled: fulfilled,
-    rejected: rejected
+    rejected: rejected,
+    synchronous: options ? options.synchronous : false,
+    runWhen: options ? options.runWhen : null
   });
   return this.handlers.length - 1;
 };