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>

test/specs/adapter.spec.js

@@ -1,19 +1,98 @@
 var axios = require('../../index');
 
 describe('adapter', function () {
-  it('should support custom adapter', function (done) {
-    var called = false;
+  beforeEach(function () {
+    jasmine.Ajax.install();
+  });
 
+  afterEach(function () {
+    jasmine.Ajax.uninstall();
+  });
+
+  it('should support custom adapter', function (done) {
     axios('/foo', {
-      adapter: function (config) {
-        called = true;
+      adapter: function barAdapter(config) {
+        return new Promise(function dispatchXhrRequest(resolve) {
+          var request = new XMLHttpRequest();
+          request.open('GET', '/bar');
+
+          request.onreadystatechange = function () {
+            resolve({
+              config: config,
+              request: request
+            });
+          };
+
+          request.send(null);
+        });
       }
+    }).catch(console.log);
+
+    getAjaxRequest().then(function(request) {
+      expect(request.url).toBe('/bar');
+      done();
+    });
+  });
+
+  it('should execute adapter code synchronously', function (done) {
+    var asyncFlag = false;
+    axios('/foo', {
+      adapter: function barAdapter(config) {
+        return new Promise(function dispatchXhrRequest(resolve) {
+          var request = new XMLHttpRequest();
+          request.open('GET', '/bar');
+
+          request.onreadystatechange = function () {
+            resolve({
+              config: config,
+              request: request
+            });
+          };
+
+          expect(asyncFlag).toBe(false);
+          request.send(null);
+        });
+      }
+    }).catch(console.log);
+
+    asyncFlag = true;
+
+    getAjaxRequest().then(function() {
+      done();
+    });
+  });
+
+  it('should execute adapter code asynchronously when interceptor is present', function (done) {
+    var asyncFlag = false;
+
+    axios.interceptors.request.use(function (config) {
+      config.headers.async = 'async it!';
+      return config;
     });
 
-    setTimeout(function () {
-      expect(called).toBe(true);
+    axios('/foo', {
+      adapter: function barAdapter(config) {
+        return new Promise(function dispatchXhrRequest(resolve) {
+          var request = new XMLHttpRequest();
+          request.open('GET', '/bar');
+
+          request.onreadystatechange = function () {
+            resolve({
+              config: config,
+              request: request
+            });
+          };
+
+          expect(asyncFlag).toBe(true);
+          request.send(null);
+        });
+      }
+    }).catch(console.log);
+
+    asyncFlag = true;
+
+    getAjaxRequest().then(function() {
       done();
-    }, 100);
+    });
   });
 });
-