Add ts declaration for @vue/cli-test-utils, Plugin API, Generator API

[fangbinwei]

What problem does this feature solve?

I code by vscode, and these is no code intelliSense when coding vue-cli-plugin and plugin unit test.

If ts declarations are provided, it will be helpful. I'm maintaing some vue cli plugins for some times, it's just a pain point for me.

What does the proposed API look like?

for @vue/cli-test-utils, add declaration to cli-test-utils folder, like createTestProject.d.ts, vscode can finish code completion even in .js file.

for plugin, generator api, maybe like this?

import {GeneratorAPI} from '@vue/cli'
import {PluginAPI} from '@vue/cli-service'

or

import {GeneratorAPI, PluginAPI} from '@vue/cli-types'

export =  function (api: GeneratorAPI, options: any) {

}

[shadowings-zy]

Hi, I am interested in this issue and I had generated GeneratorAPI declaration file and PluginAPI declaration file like this:

/**
 * Note: if a plugin-registered command needs to run in a specific default mode,
 * the plugin needs to expose it via `module.exports.defaultModes` in the form
 * of { [commandName]: mode }. This is because the command mode needs to be
 * known and applied before loading user options / applying plugins.
 */
declare interface PluginAPI {
  /**
   *
   * @param id
   * @param service
   */
  new (id: string, service: any);

  /**
   *
   * @param range
   */
  assertVersion(range: string): void;

  /**
   * Current working directory.
   * @return
   */
  getCwd(): any;

  /**
   * Resolve path for a project.
   *
   * @param {string} _path - Relative path from project root
   * @return {string} The resolved absolute path.
   */
  resolve(_path: string): string;

  /**
   * Check if the project has a given plugin.
   *
   * @param {string} id - Plugin id, can omit the (@vue/|vue-|@scope/vue)-cli-plugin- prefix
   * @return {boolean}
   */
  hasPlugin(id: string): boolean;

  /**
   * Register a command that will become available as `vue-cli-service [name]`.
   *
   * @param {string} name
   * @param {object} [opts]
   *   {
   *     description: string,
   *     usage: string,
   *     options: { [string]: string }
   *   }
   * @param {function} fn
   *   (args: { [string]: string }, rawArgs: string[]) => ?Promise
   */
  registerCommand(name: string, opts?: any, fn: any): void;

  /**
   * Register a function that will receive a chainable webpack config
   * the function is lazy and won't be called until `resolveWebpackConfig` is
   * called
   *
   * @param {function} fn
   */
  chainWebpack(fn: any): void;

  /**
   * Register
   * - a webpack configuration object that will be merged into the config
   * OR
   * - a function that will receive the raw webpack config.
   *   the function can either mutate the config directly or return an object
   *   that will be merged into the config.
   *
   * @param {object | function} fn
   */
  configureWebpack(fn: any): void;

  /**
   * Register a dev serve config function. It will receive the express `app`
   * instance of the dev server.
   *
   * @param {function} fn
   */
  configureDevServer(fn: any): void;

  /**
   * Resolve the final raw webpack config, that will be passed to webpack.
   *
   * @param {ChainableWebpackConfig} [chainableConfig]
   * @return {object} Raw webpack config.
   */
  resolveWebpackConfig(chainableConfig?: any): any;

  /**
   * Resolve an intermediate chainable webpack config instance, which can be
   * further tweaked before generating the final raw webpack config.
   * You can call this multiple times to generate different branches of the
   * base webpack config.
   * See https://github.com/mozilla-neutrino/webpack-chain
   *
   * @return {ChainableWebpackConfig}
   */
  resolveChainableWebpackConfig(): any;

  /**
   * Generate a cache identifier from a number of variables
   * @param id
   * @param partialIdentifier
   * @param configFiles
   * @return
   */
  genCacheConfig(id: any, partialIdentifier: any, configFiles: any): any;
}

But 'add declaration for @vue/cli-test-utils, like createTestProject.d.ts' makes me confused, because there is only a function in createTestProject.js.
We just need to add declaration for this function in the declaration file, right？
If so, I will work on it.