@gasket/plugin-command

@gasket/plugin-command

Enable plugins to inject new commands to be available for use with the Gasket CLI.

Installation

This is a default plugin in the Gasket CLI and is always available for use.

Overview

Gasket commands extend the oclif command, with methods allowing interaction with the Gasket engine. To create a new Gasket command, you must extend the base GasketCommand, and implement the gasketRun method.

class MyCommand extends GasketCommand {

  /**
   * Method requires implementation
   * @override
   */
  async gasketRun() {
    const { special } = this.parsed.flags;
    await this.gasket.exec('example', { special })
  }

  /**
   * Method can optionally overridden to adjust config
   * @param {Object} gasketConfig
   * @returns {Promise<Object>} modified config
   * @override
   */
  async gasketConfigure(gasketConfig) {
    return {
      ...gasketConfig,
      extra: true 
    }
  }
}

MyCommand.id = 'my-cmd';
MyCommand.description = 'My first command which executes the `example` lifecycle';
MyCommand.flags = {
  special: flags.boolean({
    default: false,
    description: 'Is this run particularly special'
  })
};

While the gasketRun method must be implemented, the gasketConfigure method can be optionally overridden and is available for commands to adjust the Gasket config, before environment overrides are applied.

The static id property, is the name of the command which will be used with the Gasket CLI in your app. For example npx gasket my-cmd. The description property will show up during npx gasket help.

In the above example, you can see we are adding a "special" flag which can be used with this command. Flags are described using the oclif flags utility made available to the getCommands lifecycle as described below. GasketCommand instances will have the the parsed arguments available as this.parsed.

To make your command available to the CLI, it needs to be returned during the getCommands lifecycle.

Lifecycles

getCommands

This lifecycle allows plugins to add commands to the CLI. This hook should return an extended GasketCommand or array of such.

// gasket-plugin-example.js
module.exports = {
  name: 'example',
  hooks: {
    /**
     * Adds my-cmd to the Gasket CLI
     * 
     * @param {Gasket} gasket - Gasket
     * @param {GasketCommand} GasketCommand - Base Gasket command to extend
     * @param {Object} flags - oclif flag types utility
     * @returns {GasketCommand|GasketCommand[]} command(s)
     */
    getCommands(gasket, { GasketCommand, flags }) {

      class MyCommand extends GasketCommand {

        async gasketRun() {
          const { special } = this.parsed.flags;
          await this.gasket.exec('example', { special });
        }
      }

      MyCommand.id = 'my-cmd';
      MyCommand.description = 'My first command which executes the `example` lifecycle';
      MyCommand.flags = {
        special: flags.boolean({
          default: false,
          description: 'Is this run particularly special'
        })
      };
      
      return [MyCommand];
    }
  }
};

In a lifecycle hook, command details can be referenced from the Gasket instance, allowing plugins to response to how the lifecycle was invoked. For example, lets make another plugin that hooks our example lifecycle from the above command.

// gasket-plugin-another.js
module.exports = {
  name: 'another-example',
  hooks: {
    async example(gasket, { special }) {
      if(special) {
        // do something special
      }
      if(gasket.command.id !== 'my-cmd') {
        // this lifecycle was invoked by some other command
      }
    }
  }
};

init

Signals the start of any Gasket command and allows running of code immediately before other gasket lifecycles. If it errors, the command will exit early.

// gasket-plugin-another.js
module.exports = {
  name: 'another-example',
  hooks: {
    async init(gasket) {
      console.log('init called for command:', gasket.command.id)
    }
  }
};

Because this lifecycle runs before for the configure lifecycle, only the partial Gasket config is available (see step 5 below).

configure

The configure lifecycle executes for each Gasket command.

Configuration for a Gasket session goes through a series of steps:

1. Config file loaded by CLI
2. Default plugins (including this) are added
3. Environment is set by base GasketCommand
4. Commands adjust config by implementing gasketConfigure
5. Environment overrides are applied by base GasketCommand
   • init lifecycle is executed
6. Plugins adjust config by hooking configure lifecycle

When the CLI starts up, it attempts to loads the gasket.config in its default expected location, or as specified with command flags. After commands have done any config adjustments, plugins then have the opportunity in this lifecycle.

// gasket-plugin-example.js
const fetch = require('@gasket/fetch');

module.exports = {
  name: 'example',
  hooks: {
    async configure(gasket, gasketConfig) {
      const { some: { serviceUrl } } = gasketConfig;
      const response = await fetch(serviceUrl);
      const remoteConfig = response.ok ? await response.json() : {};
      return {
        ...gasketConfig,
        ...remoteConfig
      };
    }
  }
};

In this example, the plugin hooks the configure lifecycle, in order to add config from a remote service. The configure lifecycle is executed with the execWaterfall method, so returning the modified config is necessary.

License

MIT