Moves vue resource docs into a new file.

Adds docs regarding handling 204 response

doc/development/fe_guide/index.md

@@ -71,6 +71,9 @@ Vue specific design patterns and practices.
 ---
+## [Vue Resource](vue_resource.md)
+Vue resource specific practices and gotchas.
+
 ## [Icons](icons.md)
 How we use SVG for our Icons.

doc/development/fe_guide/vue.md

@@ -179,6 +179,7 @@ itself, please read this guide: [State Management][state-management]
 The Service is a class used only to communicate with the server.
 It does not store or manipulate any data. It is not aware of the store or the components.
 We use [vue-resource][vue-resource-repo] to communicate with the server.
+Refer to [vue resource](vue_resource.md) for more details.
 Vue Resource should only be imported in the service file.
@@ -189,55 +190,6 @@ Vue Resource should only be imported in the service file.
   Vue.use(VueResource);
   ```
-#### Vue-resource gotchas
-#### Headers
-Headers are being parsed into a plain object in an interceptor.
-In Vue-resource 1.x `headers` object was changed into an `Headers` object. In order to not change all old code, an interceptor was added.
-
-If you need to write a unit test that takes the headers in consideration, you need to include an interceptor to parse the headers after your test interceptor.
-You can see an example in `spec/javascripts/environments/environment_spec.js`:
-  ```javascript
-  import { headersInterceptor } from './helpers/vue_resource_helper';
-
-  beforeEach(() => {
-    Vue.http.interceptors.push(myInterceptor);
-    Vue.http.interceptors.push(headersInterceptor);
-  });
-
-  afterEach(() => {
-    Vue.http.interceptors = _.without(Vue.http.interceptors, myInterceptor);
-    Vue.http.interceptors = _.without(Vue.http.interceptors, headersInterceptor);
-  });
-  ```
-
-#### `.json()`
-When making a request to the server, you will most likely need to access the body of the response.
-Use `.json()` to convert. Because `.json()` returns a Promise the follwoing structure should be used:
-
-  ```javascript
-  service.get('url')
-    .then(resp => resp.json())
-    .then((data) => {
-      this.store.storeData(data);
-    })
-    .catch(() => new Flash('Something went wrong'));
-  ```
-
-When using `Poll` (`app/assets/javascripts/lib/utils/poll.js`), the `successCallback` needs to handle `.json()` as a Promise:
-  ```javascript
-  successCallback: (response) => {
-    return response.json().then((data) => {
-      // handle the response
-    });
-  }
-  ```
-
-#### CSRF token
-We use a Vue Resource interceptor to manage the CSRF token.
-`app/assets/javascripts/vue_shared/vue_resource_interceptor.js` holds all our common interceptors.
-Note: You don't need to load `app/assets/javascripts/vue_shared/vue_resource_interceptor.js`
-since it's already being loaded by `common_vue.js`.
-
 ### End Result
 The following example shows an  application:
@@ -769,7 +721,6 @@ describe('component', () => {
 [component-system]: https://vuejs.org/v2/guide/#Composing-with-Components
 [state-management]: https://vuejs.org/v2/guide/state-management.html#Simple-State-Management-from-Scratch
 [one-way-data-flow]: https://vuejs.org/v2/guide/components.html#One-Way-Data-Flow
-[vue-resource-repo]: https://github.com/pagekit/vue-resource
 [vue-resource-interceptor]: https://github.com/pagekit/vue-resource/blob/develop/docs/http.md#interceptors
 [vue-test]: https://vuejs.org/v2/guide/unit-testing.html
 [issue-boards-service]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/assets/javascripts/boards/services/board_service.js.es6

doc/development/fe_guide/vue_resource.md

+# Vue Resouce
+In Vue applications we use [vue-resource][vue-resource-repo] to communicate with the server.
+
+## HTTP Status Codes
+
+### `.json()`
+When making a request to the server, you will most likely need to access the body of the response.
+Use `.json()` to convert. Because `.json()` returns a Promise the follwoing structure should be used:
+
+  ```javascript
+  service.get('url')
+    .then(resp => resp.json())
+    .then((data) => {
+      this.store.storeData(data);
+    })
+    .catch(() => new Flash('Something went wrong'));
+  ```
+
+
+When using `Poll` (`app/assets/javascripts/lib/utils/poll.js`), the `successCallback` needs to handle `.json()` as a Promise:
+  ```javascript
+  successCallback: (response) => {
+    return response.json().then((data) => {
+      // handle the response
+    });
+  }
+  ```
+
+### 204
+Some endpoints - usually `delete` endpoints - return `204` as the success response.
+When handling `204 - No Content` responses, we cannot use `.json()` since it tries to parse the non-existant body content.
+
+When handling `204` responses, do not use `.json`, otherwise the promise will throw an error and will enter the `catch` statement:
+
+```javascript
+  Vue.http.delete('path')
+    .then(() => {
+      // success!
+    })
+    .catch(() => {
+      // handle error
+    })
+```
+
+## Headers
+Headers are being parsed into a plain object in an interceptor.
+In Vue-resource 1.x `headers` object was changed into an `Headers` object. In order to not change all old code, an interceptor was added.
+
+If you need to write a unit test that takes the headers in consideration, you need to include an interceptor to parse the headers after your test interceptor.
+You can see an example in `spec/javascripts/environments/environment_spec.js`:
+  ```javascript
+  import { headersInterceptor } from './helpers/vue_resource_helper';
+
+  beforeEach(() => {
+    Vue.http.interceptors.push(myInterceptor);
+    Vue.http.interceptors.push(headersInterceptor);
+  });
+
+  afterEach(() => {
+    Vue.http.interceptors = _.without(Vue.http.interceptors, myInterceptor);
+    Vue.http.interceptors = _.without(Vue.http.interceptors, headersInterceptor);
+  });
+  ```
+
+## CSRF token
+We use a Vue Resource interceptor to manage the CSRF token.
+`app/assets/javascripts/vue_shared/vue_resource_interceptor.js` holds all our common interceptors.
+Note: You don't need to load `app/assets/javascripts/vue_shared/vue_resource_interceptor.js`
+since it's already being loaded by `common_vue.js`.
+
+
+[vue-resource-repo]: https://github.com/pagekit/vue-resource