1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
|
---
stage: none
group: unassigned
info: Any user with at least the Maintainer role can merge updates to this content. For details, see https://docs.gitlab.com/ee/development/development_processes.html#development-guidelines-review.
---
# Vue.js style guide
## Linting
We default to [eslint-vue-plugin](https://github.com/vuejs/eslint-plugin-vue), with the `plugin:vue/recommended`.
Check the [rules](https://github.com/vuejs/eslint-plugin-vue#bulb-rules) for more documentation.
## Basic Rules
1. The service has its own file
1. The store has its own file
1. Use a function in the bundle file to instantiate the Vue component:
```javascript
// bad
class {
init() {
new Component({})
}
}
// good
document.addEventListener('DOMContentLoaded', () => new Vue({
el: '#element',
components: {
componentName
},
render: createElement => createElement('component-name'),
}));
```
1. Do not use a singleton for the service or the store
```javascript
// bad
class Store {
constructor() {
if (!this.prototype.singleton) {
// do something
}
}
}
// good
class Store {
constructor() {
// do something
}
}
```
1. Use `.vue` for Vue templates. Do not use `%template` in HAML.
1. Explicitly define data being passed into the Vue app
```javascript
// bad
return new Vue({
el: '#element',
name: 'ComponentNameRoot',
components: {
componentName
},
provide: {
...someDataset
},
props: {
...anotherDataset
},
render: createElement => createElement('component-name'),
}));
// good
const { foobar, barfoo } = someDataset;
const { foo, bar } = anotherDataset;
return new Vue({
el: '#element',
name: 'ComponentNameRoot',
components: {
componentName
},
provide: {
foobar,
barfoo
},
props: {
foo,
bar
},
render: createElement => createElement('component-name'),
}));
```
We discourage the use of the spread operator in this specific case in
order to keep our codebase explicit, discoverable, and searchable.
This applies in any place where we would benefit from the above, such as
when [initializing Vuex state](../vuex.md#why-not-just-spread-the-initial-state).
The pattern above also enables us to easily parse non scalar values during
instantiation.
```javascript
return new Vue({
el: '#element',
name: 'ComponentNameRoot',
components: {
componentName
},
props: {
foo,
bar: parseBoolean(bar)
},
render: createElement => createElement('component-name'),
}));
```
## Naming
1. **Extensions**: Use `.vue` extension for Vue components. Do not use `.js` as file extension
([#34371](https://gitlab.com/gitlab-org/gitlab-foss/-/issues/34371)).
1. **Reference Naming**: Use PascalCase for their default imports:
```javascript
// bad
import cardBoard from 'cardBoard.vue'
components: {
cardBoard,
};
// good
import CardBoard from 'cardBoard.vue'
components: {
CardBoard,
};
```
1. **Props Naming:** Avoid using DOM component prop names.
1. **Props Naming:** Use kebab-case instead of camelCase to provide props in templates.
```html
// bad
<component class="btn">
// good
<component css-class="btn">
// bad
<component myProp="prop" />
// good
<component my-prop="prop" />
```
## Alignment
1. Follow these alignment styles for the template method:
1. With more than one attribute, all attributes should be on a new line:
```html
// bad
<component v-if="bar"
param="baz" />
<button class="btn">Click me</button>
// good
<component
v-if="bar"
param="baz"
/>
<button class="btn">
Click me
</button>
```
1. The tag can be inline if there is only one attribute:
```html
// good
<component bar="bar" />
// good
<component
bar="bar"
/>
// bad
<component
bar="bar" />
```
## Quotes
1. Always use double quotes `"` inside templates and single quotes `'` for all other JS.
```javascript
// bad
template: `
<button :class='style'>Button</button>
`
// good
template: `
<button :class="style">Button</button>
`
```
## Props
1. Props should be declared as an object
```javascript
// bad
props: ['foo']
// good
props: {
foo: {
type: String,
required: false,
default: 'bar'
}
}
```
1. Required key should always be provided when declaring a prop
```javascript
// bad
props: {
foo: {
type: String,
}
}
// good
props: {
foo: {
type: String,
required: false,
default: 'bar'
}
}
```
1. Default key should be provided if the prop is not required.
There are some scenarios where we need to check for the existence of the property.
On those a default key should not be provided.
```javascript
// good
props: {
foo: {
type: String,
required: false,
}
}
// good
props: {
foo: {
type: String,
required: false,
default: 'bar'
}
}
// good
props: {
foo: {
type: String,
required: true
}
}
```
## Data
1. `data` method should always be a function
```javascript
// bad
data: {
foo: 'foo'
}
// good
data() {
return {
foo: 'foo'
};
}
```
## Directives
1. Shorthand `@` is preferable over `v-on`
```html
// bad
<component v-on:click="eventHandler"/>
// good
<component @click="eventHandler"/>
```
1. Shorthand `:` is preferable over `v-bind`
```html
// bad
<component v-bind:class="btn"/>
// good
<component :class="btn"/>
```
1. Shorthand `#` is preferable over `v-slot`
```html
// bad
<template v-slot:header></template>
// good
<template #header></template>
```
## Closing tags
1. Prefer self-closing component tags
```html
// bad
<component></component>
// good
<component />
```
## Component usage within templates
1. Prefer a component's kebab-cased name over other styles when using it in a template
```html
// bad
<MyComponent />
// good
<my-component />
```
## Ordering
1. Tag order in `.vue` file
```html
<script>
// ...
</script>
<template>
// ...
</template>
// We don't use scoped styles but there are few instances of this
<style>
// ...
</style>
```
1. Properties in a Vue Component:
Check [order of properties in components rule](https://github.com/vuejs/eslint-plugin-vue/blob/master/docs/rules/order-in-components.md).
## `:key`
When using `v-for` you need to provide a *unique* `:key` attribute for each item.
1. If the elements of the array being iterated have an unique `id` it is advised to use it:
```html
<div
v-for="item in items"
:key="item.id"
>
<!-- content -->
</div>
```
1. When the elements being iterated don't have a unique ID, you can use the array index as the `:key` attribute
```html
<div
v-for="(item, index) in items"
:key="index"
>
<!-- content -->
</div>
```
1. When using `v-for` with `template` and there is more than one child element, the `:key` values
must be unique. It's advised to use `kebab-case` namespaces.
```html
<template v-for="(item, index) in items">
<span :key="`span-${index}`"></span>
<button :key="`button-${index}`"></button>
</template>
```
1. When dealing with nested `v-for` use the same guidelines as above.
```html
<div
v-for="item in items"
:key="item.id"
>
<span
v-for="element in array"
:key="element.id"
>
<!-- content -->
</span>
</div>
```
Useful links:
1. [Maintaining State](https://v2.vuejs.org/v2/guide/list.html#Maintaining-State)
1. [Vue Style Guide: Keyed v-for](https://vuejs.org/v2/style-guide/#Keyed-v-for-essential)
## Vue testing
Over time, a number of programming patterns and style preferences have emerged in our efforts to
effectively test Vue components. The following guide describes some of these.
**These are not strict guidelines**, but rather a collection of suggestions and good practices that
aim to provide insight into how we write Vue tests at GitLab.
### Mounting a component
Typically, when testing a Vue component, the component should be "re-mounted" in every test block.
To achieve this:
1. Create a mutable `wrapper` variable inside the top-level `describe` block.
1. Mount the component using [`mount`](https://v1.test-utils.vuejs.org/api/#mount) or [`shallowMount`](https://v1.test-utils.vuejs.org/api/#shallowMount).
1. Reassign the resulting [`Wrapper`](https://v1.test-utils.vuejs.org/api/wrapper/#wrapper) instance to our `wrapper` variable.
Creating a global, mutable wrapper provides a number of advantages, including the ability to:
- Define common functions for finding components/DOM elements:
```javascript
import MyComponent from '~/path/to/my_component.vue';
describe('MyComponent', () => {
let wrapper;
// this can now be reused across tests
const findMyComponent = wrapper.findComponent(MyComponent);
// ...
})
```
- Use a `beforeEach` block to mount the component (see
[the `createComponent` factory](#the-createcomponent-factory) for more information).
- Automatically destroy the component after the test is run with [`enableAutoDestroy`](https://v1.test-utils.vuejs.org/api/#enableautodestroy-hook)
set in [`shared_test_setup.js`](https://gitlab.com/gitlab-org/gitlab/-/blob/d0bdc8370ef17891fd718a4578e41fef97cf065d/spec/frontend/__helpers__/shared_test_setup.js#L20).
#### The `createComponent` factory
To avoid duplicating our mounting logic, it's useful to define a `createComponent` factory function
that we can reuse in each test block. This is a closure which should reassign our `wrapper` variable
to the result of [`mount`](https://v1.test-utils.vuejs.org/api/#mount) and
[`shallowMount`](https://v1.test-utils.vuejs.org/api/#shallowMount):
```javascript
import MyComponent from '~/path/to/my_component.vue';
import { shallowMount } from '@vue/test-utils';
describe('MyComponent', () => {
// Initiate the "global" wrapper variable. This will be used throughout our test:
let wrapper;
// Define our `createComponent` factory:
function createComponent() {
// Mount component and reassign `wrapper`:
wrapper = shallowMount(MyComponent);
}
it('mounts', () => {
createComponent();
expect(wrapper.exists()).toBe(true);
});
it('`isLoading` prop defaults to `false`', () => {
createComponent();
expect(wrapper.props('isLoading')).toBe(false);
});
})
```
Similarly, we could further de-duplicate our test by calling `createComponent` in a `beforeEach` block:
```javascript
import MyComponent from '~/path/to/my_component.vue';
import { shallowMount } from '@vue/test-utils';
describe('MyComponent', () => {
// Initiate the "global" wrapper variable. This will be used throughout our test
let wrapper;
// define our `createComponent` factory
function createComponent() {
// mount component and reassign `wrapper`
wrapper = shallowMount(MyComponent);
}
beforeEach(() => {
createComponent();
});
it('mounts', () => {
expect(wrapper.exists()).toBe(true);
});
it('`isLoading` prop defaults to `false`', () => {
expect(wrapper.props('isLoading')).toBe(false);
});
})
```
#### `createComponent` best practices
1. Consider using a single (or a limited number of) object arguments over many arguments.
Defining single parameters for common data like `props` is okay,
but keep in mind our [JavaScript style guide](javascript.md#limit-number-of-parameters) and
stay within the parameter number limit:
```javascript
// bad
function createComponent(data, props, methods, isLoading, mountFn) { }
// good
function createComponent({ data, props, methods, stubs, isLoading } = {}) { }
// good
function createComponent(props = {}, { data, methods, stubs, isLoading } = {}) { }
```
1. If you require both `mount` _and_ `shallowMount` within the same set of tests, it
can be useful define a `mountFn` parameter for the `createComponent` factory that accepts
the mounting function (`mount` or `shallowMount`) to be used to mount the component:
```javascript
import { shallowMount } from '@vue/test-utils';
function createComponent({ mountFn = shallowMount } = {}) { }
```
1. Use the `mountExtended` and `shallowMountExtended` helpers to expose `wrapper.findByTestId()`:
```javascript
import { shallowMountExtended } from 'helpers/vue_test_utils_helper';
import { SomeComponent } from 'components/some_component.vue';
let wrapper;
const createWrapper = () => { wrapper = shallowMountExtended(SomeComponent); };
const someButton = () => wrapper.findByTestId('someButtonTestId');
```
### Setting component state
1. Avoid using [`setProps`](https://v1.test-utils.vuejs.org/api/wrapper/#setprops) to set
component state wherever possible. Instead, set the component's
[`propsData`](https://v1.test-utils.vuejs.org/api/options.html#propsdata) when mounting the component:
```javascript
// bad
wrapper = shallowMount(MyComponent);
wrapper.setProps({
myProp: 'my cool prop'
});
// good
wrapper = shallowMount({ propsData: { myProp: 'my cool prop' } });
```
The exception here is when you wish to test component reactivity in some way.
For example, you may want to test the output of a component when after a particular watcher has
executed. Using `setProps` to test such behavior is okay.
### Accessing component state
1. When accessing props or attributes, prefer the `wrapper.props('myProp')` syntax over
`wrapper.props().myProp` or `wrapper.vm.myProp`:
```javascript
// good
expect(wrapper.props().myProp).toBe(true);
expect(wrapper.attributes().myAttr).toBe(true);
// better
expect(wrapper.props('myProp').toBe(true);
expect(wrapper.attributes('myAttr')).toBe(true);
```
1. When asserting multiple props, check the deep equality of the `props()` object with
[`toEqual`](https://jestjs.io/docs/expect#toequalvalue):
```javascript
// good
expect(wrapper.props('propA')).toBe('valueA');
expect(wrapper.props('propB')).toBe('valueB');
expect(wrapper.props('propC')).toBe('valueC');
// better
expect(wrapper.props()).toEqual({
propA: 'valueA',
propB: 'valueB',
propC: 'valueC',
});
```
1. If you are only interested in some of the props, you can use
[`toMatchObject`](https://jestjs.io/docs/expect#tomatchobjectobject). Prefer `toMatchObject`
over [`expect.objectContaining`](https://jestjs.io/docs/expect#expectobjectcontainingobject):
```javascript
// good
expect(wrapper.props()).toEqual(expect.objectContaining({
propA: 'valueA',
propB: 'valueB',
}));
// better
expect(wrapper.props()).toMatchObject({
propA: 'valueA',
propB: 'valueB',
});
```
### Testing props validation
When checking component props use `assertProps` helper. Props validation failures will be thrown as errors:
```javascript
import { assertProps } from 'helpers/assert_props'
// ...
expect(() => assertProps(SomeComponent, { invalidPropValue: '1', someOtherProp: 2 })).toThrow()
```
## The JavaScript/Vue Accord
The goal of this accord is to make sure we are all on the same page.
1. When writing Vue, you may not use jQuery in your application.
1. If you need to grab data from the DOM, you may query the DOM 1 time while bootstrapping your
application to grab data attributes using `dataset`. You can do this without jQuery.
1. You may use a jQuery dependency in Vue.js following [this example from the docs](https://vuejs.org/v2/examples/select2.html).
1. If an outside jQuery Event needs to be listen to inside the Vue application, you may use
jQuery event listeners.
1. We avoid adding new jQuery events when they are not required. Instead of adding new jQuery
events take a look at [different methods to do the same task](https://v2.vuejs.org/v2/api/#vm-emit).
1. You may query the `window` object one time, while bootstrapping your application for application
specific data (for example, `scrollTo` is ok to access anytime). Do this access during the
bootstrapping of your application.
1. You may have a temporary but immediate need to create technical debt by writing code that does
not follow our standards, to be refactored later. Maintainers need to be ok with the tech debt in
the first place. An issue should be created for that tech debt to evaluate it further and discuss.
In the coming months you should fix that tech debt, with its priority to be determined by maintainers.
1. When creating tech debt you must write the tests for that code before hand and those tests may
not be rewritten. For example, jQuery tests rewritten to Vue tests.
1. You may choose to use VueX as a centralized state management. If you choose not to use VueX, you
must use the *store pattern* which can be found in the
[Vue.js documentation](https://v2.vuejs.org/v2/guide/state-management.html#Simple-State-Management-from-Scratch).
1. Once you have chosen a centralized state-management solution you must use it for your entire
application. Don't mix and match your state-management solutions.
|