mirror of https://codeberg.org/forgejo/forgejo
137 lines
5.7 KiB
Markdown
137 lines
5.7 KiB
Markdown
---
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date: "2021-10-13T16:00:00+02:00"
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title: "Guidelines for Frontend Development"
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slug: "guidelines-frontend"
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weight: 20
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toc: false
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draft: false
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menu:
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sidebar:
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parent: "developers"
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name: "Guidelines for Frontend"
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weight: 20
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identifier: "guidelines-frontend"
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---
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# Guidelines for Frontend Development
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**Table of Contents**
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{{< toc >}}
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## Background
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Gitea uses [Fomantic-UI](https://fomantic-ui.com/introduction/getting-started.html) (based on [jQuery](https://api.jquery.com)) and [Vue3](https://vuejs.org/) for its frontend.
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The HTML pages are rendered by [Go HTML Template](https://pkg.go.dev/html/template).
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The source files can be found in the following directories:
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* **CSS styles:** `web_src/css/`
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* **JavaScript files:** `web_src/js/`
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* **Vue components:** `web_src/js/components/`
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* **Go HTML templates:** `templates/`
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## General Guidelines
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We recommend [Google HTML/CSS Style Guide](https://google.github.io/styleguide/htmlcssguide.html) and [Google JavaScript Style Guide](https://google.github.io/styleguide/jsguide.html)
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### Gitea specific guidelines:
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1. Every feature (Fomantic-UI/jQuery module) should be put in separate files/directories.
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2. HTML ids and classes should use kebab-case, it's preferred to contain 2-3 feature related keywords.
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3. HTML ids and classes used in JavaScript should be unique for the whole project, and should contain 2-3 feature related keywords. We recommend to use the `js-` prefix for classes that are only used in JavaScript.
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4. CSS styling for classes provided by frameworks should not be overwritten. Always use new class names with 2-3 feature related keywords to overwrite framework styles. Gitea's helper CSS classes in `helpers.less` could be helpful.
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5. The backend can pass complex data to the frontend by using `ctx.PageData["myModuleData"] = map[]{}`, but do not expose whole models to the frontend to avoid leaking sensitive data.
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6. Simple pages and SEO-related pages use Go HTML Template render to generate static Fomantic-UI HTML output. Complex pages can use Vue3.
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7. Clarify variable types, prefer `elem.disabled = true` instead of `elem.setAttribute('disabled', 'anything')`, prefer `$el.prop('checked', var === 'yes')` instead of `$el.prop('checked', var)`.
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8. Use semantic elements, prefer `<button class="ui button">` instead of `<div class="ui button">`.
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9. Avoid unnecessary `!important` in CSS, add comments to explain why it's necessary if it can't be avoided.
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10. Avoid mixing different events in one event listener, prefer to use individual event listeners for every event.
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11. Custom event names are recommended to use `ce-` prefix.
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### Accessibility / ARIA
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In history, Gitea heavily uses Fomantic UI which is not an accessibility-friendly framework.
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Gitea uses some patches to make Fomantic UI more accessible (see the `aria.js` and `aria.md`),
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but there are still many problems which need a lot of work and time to fix.
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### Framework Usage
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Mixing different frameworks together is discouraged, it makes the code difficult to be maintained.
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A JavaScript module should follow one major framework and follow the framework's best practice.
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Recommended implementations:
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* Vue + Vanilla JS
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* Fomantic-UI (jQuery)
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* Vanilla JS
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Discouraged implementations:
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* Vue + Fomantic-UI (jQuery)
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* jQuery + Vanilla JS
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To make UI consistent, Vue components can use Fomantic-UI CSS classes.
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Although mixing different frameworks is discouraged,
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it should also work if the mixing is necessary and the code is well-designed and maintainable.
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### `async` Functions
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Only mark a function as `async` if and only if there are `await` calls
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or `Promise` returns inside the function.
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It's not recommended to use `async` event listeners, which may lead to problems.
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The reason is that the code after await is executed outside the event dispatch.
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Reference: https://github.com/github/eslint-plugin-github/blob/main/docs/rules/async-preventdefault.md
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If an event listener must be `async`, the `e.preventDefault()` should be before any `await`,
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it's recommended to put it at the beginning of the function.
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If we want to call an `async` function in a non-async context,
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it's recommended to use `const _promise = asyncFoo()` to tell readers
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that this is done by purpose, we want to call the async function and ignore the Promise.
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Some lint rules and IDEs also have warnings if the returned Promise is not handled.
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### HTML Attributes and `dataset`
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The usage of `dataset` is forbidden, its camel-casing behaviour makes it hard to grep for attributes.
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However, there are still some special cases, so the current guideline is:
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* For legacy code:
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* `$.data()` should be refactored to `$.attr()`.
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* `$.data()` can be used to bind some non-string data to elements in rare cases, but it is highly discouraged.
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* For new code:
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* `node.dataset` should not be used, use `node.getAttribute` instead.
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* never bind any user data to a DOM node, use a suitable design pattern to describe the relation between node and data.
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### Show/Hide Elements
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* Vue components are recommended to use `v-if` and `v-show` to show/hide elements.
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* Go template code should use Gitea's `.gt-hidden` and `showElem()/hideElem()/toggleElem()`, see more details in `.gt-hidden`'s comment.
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### Styles and Attributes in Go HTML Template
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It's recommended to use:
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```html
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<div class="gt-name1 gt-name2 {{if .IsFoo}}gt-foo{{end}}" {{if .IsFoo}}data-foo{{end}}></div>
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```
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instead of:
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```html
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<div class="gt-name1 gt-name2{{if .IsFoo}} gt-foo{{end}}"{{if .IsFoo}} data-foo{{end}}></div>
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```
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to make the code more readable.
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### Legacy Code
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A lot of legacy code already existed before this document's written. It's recommended to refactor legacy code to follow the guidelines.
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### Vue3 and JSX
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Gitea is using Vue3 now. We decided not to introduce JSX to keep the HTML and the JavaScript code separated.
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