creating-plugins.md

Read this on the main serverless docs site

Creating custom plugins

Creating a custom plugin lets you:

• Hook into lifecycle events to add new logic
• Define new CLI commands
• Define new variable sources
• Extend the serverless.yml syntax
• Write extra information to the CLI output
• Add support for new cloud providers

Creating a plugin

The simplest way to create a Serverless Framework plugin is to write a JavaScript file:

'use strict';

class MyPlugin {
  constructor() {
    // The plugin is loaded
  }
}

module.exports = MyPlugin;

The plugin can then be loaded in serverless.yml via a local path:

# serverless.yml
service: app

functions:
  # ...

plugins:
  - ./my-plugin.js

Distributing a plugin via NPM

Plugins can also be published to NPM and later installed in separate projects.

To correctly configure the plugin's NPM package, set the main property to point to your plugin file in package.json:

{
  "main": "my-plugin.js"
}

It is also a good practice to add serverless to the peerDependencies section. That ensures that your plugin runs only with the Serverless Framework versions it supports.

{
  ...
  "peerDependencies": {
    "serverless": "^2.60 || 3"
  }
}

Once the plugin is published on NPM, follow the documentation on Installing plugins to use the custom plugin.

Lifecycle events

Lifecycle events are events that fire sequentially during a CLI command.

Additionally, for each event an additional before and after event is created. For example:

• before:package:package
• package:package
• after:package:package
• before:deploy:deploy
• deploy:deploy
• after:deploy:deploy

The initialize event is shared across all CLI commands and runs when the CLI starts.

Plugins can "hook" into existing lifecycle events to add behavior to commands like deploy, package, etc. via the hooks helper:

'use strict';

class MyPlugin {
  constructor() {
    this.hooks = {
      'initialize': () => this.init(),
      'before:deploy:deploy': () => this.beforeDeploy(),
      'after:deploy:deploy': () => this.afterDeploy(),
    };
  }

  init() {
    // Initialization
  }

  beforeDeploy() {
    // Before deploy
  }

  afterDeploy() {
    // After deploy
  }
}

module.exports = MyPlugin;

Plugins can also create their own commands (with their own lifecycle events): read the Custom commands documentation.

Serverless instance

The serverless parameter provides access to the service configuration at runtime:

'use strict';

class MyPlugin {
  constructor(serverless) {
    this.serverless = serverless;
    this.hooks = {
      initialize: () => this.init(),
    };
  }

  init() {
    console.log('Serverless instance: ', this.serverless);

    // `serverless.service` contains the (resolved) serverless.yml config
    const service = this.serverless.service;
    console.log('Provider name: ', service.provider.name);
    console.log('Functions: ', service.functions);
  }
}

module.exports = MyPlugin;

Note: configuration values are only resolved after plugins are initialized. Do not try to read configuration in the plugin constructor, as variables aren't resolved yet. Read configuration in lifecycle events only.

CLI options

The options parameter provides access to the CLI options provided to the command:

class MyPlugin {
  constructor(serverless, options) {
    // Log if a --verbose option was passed:
    console.log(options.verbose);
  }
}

Provider-specific plugins

Plugins can be provider specific, which means that run only with a specific provider.

Note: Binding a plugin to a provider is optional. Serverless will always consider your plugin if you don't specify a provider.

To bind to a specific provider, retrieve it and set the this.provider property in the plugin constructor:

class MyPlugin {
  constructor(serverless, options) {
    // bind to a specific provider
    this.provider = serverless.getProvider('providerX');

    // ...
  }
}

The plugin will now only be executed when the service's provider matches the given provider.

ESM plugins

If you use Node.js v12.22 or later, ESM plugins are also supported.

export default class MyPlugin {
  constructor() {
    // The plugin is loaded
  }
}