Edit

Running Commands Programmatically

If you need to run a command from another, or programmatically run a command in another codebase, there are a couple options.

First, it is generally a bad idea to run a command directly as the command exports a user interface, not a code interface. It's a design smell that should rarely (if ever) be used. Generally speaking, it's better to break up the code so that it can be called directly rather than as a command. We'll show this better method first.

Sharing code with modules

For example, if we use heroku config as an example, we could have a command that outputs the config vars of an app to the screen like this:

./src/commands/config.ts

export class HerokuConfig extends Command {
  static flags = {
    app: Flags.string({required: true})
  }

  async run() {
    const {flags} = this.parse(HerokuConfig)
    const config = await api.get(`/apps/${flags.app}/config-vars`)
    for (let [key, value] of Object.entries(config)) {
      this.log(`${key}=${value}`)
    }
  }
}

If we had another command such as heroku release that would do some logic then display these commands using the same logic, we should create a new module that we could call directly:

./src/commands/release.ts

import {displayConfigVars} from '../display_config_vars'

export class HerokuRelease extends Command {
  static flags = {
    app: Flags.string({required: true})
  }

  async run() {
    const {flags} = this.parse(HerokuRelease)
    await this.doRelease(flags.app)
    await displayConfigVars(flags.app)
  }
}

./src/display_config_vars.ts

export async function displayConfigVars(app: string) {
  const config = await api.get(`/apps/${app}config-vars`)
  for (let [key, value] of Object.entries(config)) {
    this.log(`${key}=${value}`)
  }
}

This is the recommended way to share code. This can be extended further by putting shared code into its own npm package.

Calling commands directly

Still, if you really want to call a command directly, it's easy to do. For this, we could write our heroku release command like so:

./src/commands/release.ts

import {HerokuConfig} from './config'

export class HerokuRelease extends Command {
  static flags = {
    app: Flags.string({required: true})
  }

  async run() {
    const {flags} = this.parse(HerokuRelease)
    await this.doRelease(flags.app)
    await HerokuConfig.run(['--app', flags.app])
  }
}

This works because commands have a static .run() method on them that can be used to instantiate the command and run the instance .run() method. It takes in the argv as input to the command.

This works for both multi and single command CLIs.