feat(cli,cli-service,cli-test-utils): add ts declaration

[fangbinwei]

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Docs
• Underlying tools
• Other, please describe:

Does this PR introduce a breaking change? (check one)

• Yes
• No

Other information:
for issue #5324 , I have added some ts declarations

• GeneratorAPI, PromptModuleAPI in @vue/cli
• PluginAPI in @vue/cli-service
• test utilities function declaration in @vue/cli-test-utils

I added test for these declarations. Also I linted the code by dtslint with some necessary rules according to the README of DefinitelyTyped .

test by npx tsc -p packages/@vue/cli/types/tsconfig.json

known issue

It seems there are some problem in webpack's declaration. so "skipLibCheck": true should be set in tsconfig.json when use PluginAPI in .ts.

---

By the way, I formated and linted the codes whithout adding config file (like tslint.json, .prettierrc) to vue-cli repo. Besides, vscode may report error for *.d.ts caused by eslint parser of cli repo. I believe I should avoid adding extra config files/codes or changing eslintignore. Core maintaner do this will be better, if necessary.

Add I used yarn link to verify the declarations of @vue/cli, @vue/cli-service, @vue/cli-test-utils in my own plugin repo.

• vscode can finish code completion even in .js file according declaration of @vue/cli-test-utils
• PluginAPI and GeneratorAPI can be used in .ts file normally

I hope this pr will be helpful.

appendix

for @vue/cli-test-utils,I added declaration to cli-test-utils folder directly, like createTestProject.d.ts

We can organize the file structure better, but It may cause break change. Or there is good way I overlooked.

[fangbinwei]

known issue
It seems there are some problem in webpack's declaration. so "skipLibCheck": true should be set in tsconfig.json when use PluginAPI in .ts

The problem come from here

vue-cli/packages/@vue/cli-service/types/ProjectOptions.d.ts

Line 2 in bd7ad93

import { WebpackOptions } from 'webpack/declarations/WebpackOptions'

if I change code to

import { Configuration as WebpackOptions } from 'webpack' // it will use @types/webpack

tsc -p packages/@vue/cli-service/types/tsconfig.json will be ok without "skipLibCheck": true

The key to the problem is which to use, @types/webpack or webpack/declarations/WebpackOptions

[fangbinwei]

Usage in *.js

maybe it's worth mentioning in the documentation, vscode can provide completions in this way.

service plugin

index.js

/** @type {import('@vue/cli-service').ServicePlugin} */
module.exports = (api, options) => {

}

generator plugin

generator/index.js

/** @type {import('@vue/cli').GeneratorPlugin} */
module.exports = (api) => {
}

project config

vue.config.js

/** @type {import('@vue/cli-service').ProjectOptions} */
module.exports = {
  // options...
}

https://www.typescriptlang.org/docs/handbook/type-checking-javascript-files.html

[haoqunjiang]

Thanks for the great help!

Please also fix the merge conflicts with the dev branch and I think we'll be good to go.