195 lines
8 KiB
Markdown
195 lines
8 KiB
Markdown
# Frontend FAQ
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## Rules of Frontend FAQ
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1. **You talk about Frontend FAQ.**
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Please share links to it whenever applicable, so more eyes catch when content
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gets outdated.
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1. **Keep it short and simple.**
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Whenever an answer needs more than two sentences it does not belong here.
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1. **Provide background when possible.**
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Linking to relevant source code, issue / epic, or other documentation helps
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to understand the answer.
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1. **If you see something, do something.**
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Please remove or update any content that is outdated as soon as you see it.
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## FAQ
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### 1. How do I find the Rails route for a page?
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#### Check the 'page' data attribute
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The easiest way is to type the following in the browser while on the page in
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question:
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```javascript
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document.body.dataset.page
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```
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Find here the [source code setting the attribute](https://gitlab.com/gitlab-org/gitlab/blob/cc5095edfce2b4d4083a4fb1cdc7c0a1898b9921/app/views/layouts/application.html.haml#L4).
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#### Rails routes
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The `rake routes` command can be used to list all the routes available in the application, piping the output into `grep`, we can perform a search through the list of available routes.
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The output includes the request types available, route parameters and the relevant controller.
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```shell
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bundle exec rake routes | grep "issues"
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```
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### 2. `modal_copy_button` vs `clipboard_button`
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The `clipboard_button` uses the `copy_to_clipboard.js` behavior, which is
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initialized on page load, so if there are vue-based clipboard buttons that
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don't exist at page load (such as ones in a `GlModal`), they do not have the
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click handlers associated with the clipboard package.
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`modal_copy_button` was added that manages an instance of the
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[`clipboard` plugin](https://www.npmjs.com/package/clipboard) specific to
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the instance of that component, which means that clipboard events are
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bound on mounting and destroyed when the button is, mitigating the above
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issue. It also has bindings to a particular container or modal ID
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available, to work with the focus trap created by our GlModal.
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### 3. A `gitlab-ui` component not conforming to [Pajamas Design System](https://design.gitlab.com/)
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Some [Pajamas Design System](https://design.gitlab.com/) components implemented in
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`gitlab-ui` do not conform with the design system specs because they lack some
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planned features or are not correctly styled yet. In the Pajamas website, a
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banner on top of the component examples indicates that:
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> This component does not yet conform to the correct styling defined in our Design
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> System. Refer to the Design System documentation when referencing visuals for this
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> component.
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For example, at the time of writing, this type of warning can be observed for
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[all form components](https://design.gitlab.com/components/forms/). It, however,
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doesn't imply that the component should not be used.
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GitLab always asks to use `<gl-*>` components whenever a suitable component exists.
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It makes codebase unified and more comfortable to maintain/refactor in the future.
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Ensure a [Product Designer](https://about.gitlab.com/company/team/?department=ux-department)
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reviews the use of the non-conforming component as part of the MR review. Make a
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follow up issue and attach it to the component implementation epic found within the
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[Components of Pajamas Design System epic](https://gitlab.com/groups/gitlab-org/-/epics/973).
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### 4. My submit form button becomes disabled after submitting
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If you are using a submit button inside a form and you attach an `onSubmit` event listener on the form element, [this piece of code](https://gitlab.com/gitlab-org/gitlab/blob/794c247a910e2759ce9b401356432a38a4535d49/app/assets/javascripts/main.js#L225) will add a `disabled` class selector to the submit button when the form is submitted.
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To avoid this behavior, add the class `js-no-auto-disable` to the button.
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### 5. Should I use a full URL (i.e. `gon.gitlab_url`) or a full path (i.e. `gon.relative_url_root`) when referencing backend endpoints?
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It's preferred to use a **full path** over a **full URL** because the URL will use the hostname configured with
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GitLab which may not match the request. This will cause [CORS issues like this Web IDE one](https://gitlab.com/gitlab-org/gitlab/-/issues/36810).
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Example:
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```javascript
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// bad :(
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// If gitlab is configured with hostname `0.0.0.0`
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// This will cause CORS issues if I request from `localhost`
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axios.get(joinPaths(gon.gitlab_url, '-', 'foo'))
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// good :)
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axios.get(joinPaths(gon.relative_url_root, '-', 'foo'))
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```
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Also, please try not to hardcode paths in the Frontend, but instead receive them from the Backend (see next section).
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When referencing Backend rails paths, avoid using `*_url`, and use `*_path` instead.
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Example:
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```haml
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-# Bad :(
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#js-foo{ data: { foo_url: some_rails_foo_url } }
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-# Good :)
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#js-foo{ data: { foo_path: some_rails_foo_path } }
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```
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### 6. How should the Frontend reference Backend paths?
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We prefer not to add extra coupling by hardcoding paths. If possible,
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add these paths as data attributes to the DOM element being referenced in the JavaScript.
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Example:
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```javascript
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// Bad :(
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// Here's a Vuex action that hardcodes a path :(
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export const fetchFoos = ({ state }) => {
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return axios.get(joinPaths(gon.relative_url_root, '-', 'foo'));
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};
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// Good :)
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function initFoo() {
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const el = document.getElementById('js-foo');
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// Path comes from our root element's data which is used to initialize the store :)
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const store = createStore({
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fooPath: el.dataset.fooPath
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});
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Vue.extend({
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store,
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el,
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render(h) {
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return h(Component);
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},
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});
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}
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// Vuex action can now reference the path from its state :)
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export const fetchFoos = ({ state }) => {
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return axios.get(state.settings.fooPath);
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};
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```
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### 7. How can I test the production build locally?
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Sometimes it's necessary to test locally what the frontend production build would produce, to do so the steps are:
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1. Stop webpack: `gdk stop webpack`.
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1. Open `gitlab.yaml` located in your `gitlab` installation folder, scroll down to the `webpack` section and change `dev_server` to `enabled: false`.
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1. Run `yarn webpack-prod && gdk restart rails-web`.
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The production build takes a few minutes to be completed; any code change at this point will be
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displayed only after executing the item 3 above again.
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To return to the normal development mode:
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1. Open `gitlab.yaml` located in your `gitlab` installation folder, scroll down to the `webpack` section and change back `dev_server` to `enabled: true`.
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1. Run `yarn clean` to remove the production assets and free some space (optional).
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1. Start webpack again: `gdk start webpack`.
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1. Restart GDK: `gdk restart rails-web`.
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### 8. Babel polyfills
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> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/28837) in GitLab 12.8.
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GitLab has enabled the Babel `preset-env` option
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[`useBuiltIns: 'usage'`](https://babeljs.io/docs/en/babel-preset-env#usebuiltins-usage),
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which adds the appropriate `core-js` polyfills once for each JavaScript feature
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we're using that our target browsers don't support. You don't need to add `core-js`
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polyfills manually.
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NOTE: **Note:**
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GitLab still manually adds non-`core-js` polyfills for extending browser features
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(such as GitLab's SVG polyfill) that allow us reference SVGs by using `<use xlink:href>`.
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These polyfills should be added to `app/assets/javascripts/commons/polyfills.js`.
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To see what polyfills are being used:
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1. Navigate to your merge request.
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1. In the secondary menu below the title of the merge request, click **Pipelines**, then
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click the pipeline you want to view, to display the jobs in that pipeline.
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1. Click the [`compile-production-assets`](https://gitlab.com/gitlab-org/gitlab/-/jobs/641770154) job.
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1. In the right-hand sidebar, scroll to **Job Artifacts**, and click **Browse**.
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1. Click the **webpack-report** folder to open it, and click **index.html**.
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1. In the upper left corner of the page, click the right arrow **{angle-right}**
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to display the explorer.
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1. In the **Search modules** field, enter `gitlab/node_modules/core-js` to see
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which polyfills are being loaded and where:
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