Angular CLI Packagr Tasks

Tasks & Workflow for ng-packagr.

ng-packagr works like a classic task manager, running task in a certain order that is required to create an angular package. It also provides the logic for all tasks internally, based on the angular package format spec.

This closed box does its job well, but what if we want additional steps before/after the packaging? What if we want to change the order, behaviour or logic of each step within the packagr? How can we filter certain packages from building (secondary), etc...

ng-packger supports this through a programmatic API that is not accessible when using it through the angular-cli, this is where ng-cli-packagr-tasks comes in.

Install

yarn add ng-cli-packagr-tasks -D

Configuration

Here is a simple CLI configuration for a library (angular.json):

"architect": {
  "build": {
    "builder": "@angular-devkit/build-ng-packagr:build",
    "options": {
      "tsConfig": "tsconfig.lib.json",
      "project": "ng-package.json"
    },
    "configurations": {
      "production": {
        "project": "ng-package.prod.json"
      }
    }
  }
}

This will run the classic ng-packagr build process.

Let's update it a bit:

"architect": {
  "build": {
    "builder": "ng-cli-packagr-tasks:build",
    "options": {
      "tsConfig": "tsconfig.lib.json",
      "project": "ng-package.json",
      "transformConfig": "ng-packagr.transformers.ts"
    },
    "configurations": {
      "production": {
        "project": "ng-package.prod.json"
      }
    }
  }
}

We've introduces 2 changes:

• The builder has changed from @angular-devkit/build-ng-packagr:build to ng-cli-packagr-tasks:build.
• The property transformConfig was added, pointing to a configuration module where we can tweak the process.

Note that ng-packagr itself does not change, only the architect builder.

Configuration module

The configuration module is a simple JS (or TS) file that exports (default) the transformation instructions, there are 2 ways:

• Direct transformer hook configuration (NgPackagerTransformerHooks)
• A function that returns a transformer hook configuration or a Promise. () => NgPackagerTransformerHooks | Promise<NgPackagerTransformerHooks>

This is Similar to webpack

Regardless of how you choose to export the instructions (function or object), the end result is always the NgPackagerTransformerHooks

When using a function, an additional context parameter is provided, holding the root directory and a logger.

Packagr tasks (NgPackagerTransformerHooks)

ng-packagr run tasks, in a certain order, that together form the process of creating a library in the angular package format spec.

NgPackagerTransformerHooks is a map of hooks within the packaging process that you can tap in to, each hook correspond to a specific packagr task.

export interface NgPackagerTransformerHooks {
  initTsConfig?: TransformerHook<TaskContext<[ParsedConfiguration]>>;
  analyseSources?: TransformerHook<TaskContext>;
  entryPoint?: TransformerHook;
  compileNgc?: TransformerHook;
  writeBundles?: TransformerHook;
  writePackage?: TransformerHook;
}

The order which the tasks run reflect in the order of the properties above.

For example, compileNgc will compile the library (TS -> JS, twice in 2 formats).

ng-packager has more tasks, running before analyseSources but they do not provide any value for customization.

Task phases (TransformerHook)

For each hook there are 3 phases which you can register (all optional): before, replace and after

export interface TransformerHook<T> {
  before?: HookHandler<T>;
  replace?: HookHandler<T>;
  after?: HookHandler<T>;
}

The order which the phases run are: before -> replace -> after

The timeline is relative to the replace phase, which is where the original ng-packagr task runs. If you set a hook handler in replace the original task from ng-packagr WILL NOT RUN.

Do not set a handler in replace unless you really know what you are doing!

Each HookHandler is a function that handles handles that hook:

export type HookHandler<T> = (taskContext: T) => BuildGraph | undefined | Promise<BuildGraph | undefined>;

The hook is invoked with a taskContext parameter. We can see from the generic (T) that there is more then one types of handler, there are 2:

/**
 * A context for hooks running at the initialization phase, when all entry points are discovered and all initial values are loaded.
 */
export interface TaskContext<T = any[]> {
  factoryInjections: T;
  graph: BuildGraph;
}

/**
 * A context for hook handlers running at the processing phase, where each entry point is being processed in a sequence, one after the other.
 */
export interface EntryPointTaskContext<T = any[]> extends TaskContext<T> {
  epNode: EntryPointNode;
}

EntryPointTaskContext handlers are called multiple times, once for every package (primary and secondary). TaskContext is called once before starting to process packages

Examples

Before we dive into examples, it's important that we understand what information is available to us, provided by ng-packagr.

Most of it is stored in EntryPointNode. The EntryPointNode object contains a lot of things. File path locations (sources, destinations), cached files, cache TS compiler programs and more...

If we want to copy or move files, delete, build something etc, we need to know where the resources are located...

There isn't much documentation, but it is typed which should be enough.

• Filtering build of packages
• Copy file to built packages
• API Metadata generator
• Modify TS compilation settings in secondary entry points

TODO:

• Example on information in EntryPointNode (destination, metadata etc...)
• Example for theme builder (e.g. scss)