Hooks

oclif exposes lifecycle event hooks such as init and command_not_found. See below for a list of all the lifecycle events. In addition to these built-in events, you can create your own events and allow commands/plugins to watch for these custom events. It's a great way to allow multiple plugins to interact with each other.

Multiple hooks are run in parallel. This behavior may change in a future release.

A basic hook looks like the following in TypeScript:

import {Hook} from '@oclif/core'

const hook: Hook<'init'> = async function (options) {
  console.log(`example init hook running before ${options.id}`)
}

export default hook

The hook must also be declared with the event's name and hook's file path under oclif's settings in package.json:

"oclif": {
  "commands": "./lib/commands",
  "hooks": {
    "init": "./lib/hooks/init/example"
  }
}

Multiple hooks of the same event type can be declared with an array.

"oclif": {
  "commands": "./lib/commands",
  "hooks": {
    "init": [
      "./lib/hooks/init/example",
      "./lib/hooks/init/another_hook"
    ]
  }
}

You can create hooks with oclif generate hook myhook --event=init.

Lifecycle Events

• init - runs when the CLI is initialized before a command is found to run
• prerun - runs after init and after the command is found, but just before running the command itself
• command_not_found - runs if a command is not found before the error is displayed
• command_incomplete - runs if a command is not found but it is a partial of an existing command. Only works if flexible taxonomy is enabled. Useful for instances where you'd like to present a prompt with all the matching commands. See Salesforce CLI's implementation.
• jit_plugin_not_installed - runs if a command from a JIT plugin is executed but the plugin isn't installed yet. See Salesforce CLI's implementation.
• preparse - runs before flags and args are parsed and validated. Useful if you need to manipulate the input. See Salesforce CLI's implementation. This can only be implemented by the root CLI.
• postrun - runs after the command only if the command finishes with no error

Custom Events

Custom events are just like lifecycle events, but you need to call this.config.runHook() to fire the event.

For example, you could define an analytics post function that you will run in your command after submitting analytics telemetry. First define:

src/hooks/analytics/post.ts

const hook = async function (options: {id: string}) {
  // code to post options.id to analytics server
}

export default hook

package.json

  "oclif": {
    "commands": "./lib/commands",
    "hooks": {
      "analytics": "./lib/hooks/analytics/post"
    },
  },

Then in any command you want to trigger the event:

export class extends Command {
  async run() {
    // emit analytics
    await this.config.runHook('analytics', {id: 'my_command'})
  }
}

If you need to exit during a hook, use options.context.error() or options.context.exit(). Throwing an Error will not cause the CLI to exit - this is to prevent an issues such a single plugin's init hook causing a CLI to immediately fail on every command execution.