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Before and After Lifecycle Functions

All events expose an identical interface with two functions that can be handled by the plugin and responsible for a different step in the lifecycle of the event. One for "before" the event is emitted and another for "after" the event is emitted.

Event Structure and Parameters​

export interface PluginEventType<T extends EventParams> {
  before?: PluginBeforeEvent<T>;
  after?: PluginAfterEvent<T>;
}

For each event, the type of EventParams is different, providing access to relevant data for the specific event.

export interface EventParams {}

Before and After Function Signatures​

export type PluginBeforeEvent<T extends EventParams> = (
  dsgContext: DsgContext,
  eventParams: T
) => Promisable<T>;

// Node.js [version](https://github.com/amplication/amplication/blob/master/libs/util/code-gen-types/src/plugins.types.ts#L21)
export type PluginAfterEvent<T extends EventParams> = (
  dsgContext: DsgContext,
  eventParams: T,
  modules: ModuleMap
) => Promisable<ModuleMap>;

// .NET [version](https://github.com/amplication/amplication/blob/master/libs/util/code-gen-types/src/dotnet-plugins.types.ts#L22)
export type PluginAfterEvent<T extends EventParams, F> = (
  dsgContext: DsgContext,
  eventParams: T,
  files: FileMap<F>
) => Promisable<FileMap<F>>;

In the before and after functions, we have an access to the context and the event params. The context is used to gather common parts between events. The event params manipulate the default behavior by passing different values.

Accessing and Modifying Generated Files​

In the after function, we also have access to the generated files. An example of using this parameter is when you want to restructure the generated files in a different folder structure.

info

In the after function for .NET plugins, we use a FileMap. For Node.js plugins' after function we use a ModuleMap.

Function Examples​

Most of the functions include examples. But, if you're looking for more comprehensive and real-world examples, you can explore the code of the Amplication plugins directly. These plugins showcase various implementations and use cases for the before and after lifecycle functions.

Best Practices and Cautions​

  1. In the after function, avoid unintentionally overriding the entire generated file. Opt for smaller changes instead.
  2. In the before function, take care when modifying templates to not unintentionally affect code generation.
  3. In the before function, only choose skipDefaultBehavior if skipping code generation entirely, including default generation, is intended.