This is a plugin that only has a peer dependency to piral-core. What piral-lazy brings to the table is a set of Pilet API extensions that can be used with piral or piral-core.

The set includes a fromLazy shortcut.

By default, these API extensions are not integrated in piral, so you'd need to add them to your Piral instance. We recommend integrating piral-lazy when you think about an opt-in for any third-party framework (e.g., piral-vue, piral-ng, ...).

Lazy loading of data or other dependencies can be crucial in more complex scenarios. It should not be necessary to include everything in one load to bring a pilet or components of it to live.

piral-lazy allows defining generic dependencies that will be loaded before loading/using a component. The provided helpers which are exposed via the pilet API give you the power to

1. define new dependencies (given by a unique name and a loader function) and
2. rely on defined dependencies before actually loading/trying to render a component.

If your pilets use lazy loading in some way then piral-lazy may be the right choice. Also, if your pilets are too large and could benefit from further resource sharing and lazy loading then this plugin could be helpful. piral-lazy remains framework agnostic and thus works beyond React.

Alternative: Just define/use what is there out of the box. By using React.lazy together with bundle splitting most of the things may be already properly transported. Remember that you could also lazy load context that provide your dependencies - thus making React.lazy a single solution (if your framework is "React").

The following functions are brought to the Pilet API.

Allows to define lazy loading dependencies in form of lazy loading functions. This can be used to ensure certain data is available or that certain modules are already loaded.

A simple example:

import { PiletApi } from '<name-of-piral-instance>';

export function setup(piral: PiletApi) {
  piral.defineDependency('lodash', () => import('https://cdn.jsdelivr.net/npm/lodash@4.17.15/lodash.min.js'));
}

Transforms the result of a promise derived from a callback (i.e., lazy loading) to a proper component. This is thought for non-React lazy loading. For React you'll need to use the known way of applying React.lazy to your component initialization.

::: summary: For pilet authors

You can use the fromLazy function from the Pilet API to convert your lazy loaded components to components usable by your Piral instance.

Example use:

import { PiletApi } from '<name-of-piral-instance>';

export function setup(piral: PiletApi) {
  const LazyPage = piral.fromLazy(() => import('./MyPage'));
  piral.registerPage('/sample', LazyPage);
}

Remark: For React components React.lazy should be preferred. The provided lazy loading wrapper should only be used for third-party components that require a converter.

For lazy loading externals we recommend a combination with import maps. These can be set up in package.json as simple as follows:

{
  "name": "my-pilet",
  "version": "1.0.0",
  "importmap": {
    "imports": {
      "lodash": "./node_modules/lodash/index.js"
    }
  }
}

Now we can actually use this in combination with defineDependency:

import { PiletApi } from '<name-of-piral-instance>';

export function setup(piral: PiletApi) {
  const loadFromImport = (name: string) => require('importmap').ready(name);
  piral.defineDependency('lodash', () => loadFromImport('lodash'));
  const LazyPage = piral.fromLazy(() => import('./MyPage'), ['lodash']);
  piral.registerPage('/sample', LazyPage);
}

Important: You'll either need to use import maps or externals in your package.json to be able to use require or import from in your lazy loaded bundles. Otherwise, the noted packages will be fixed bundled in. If you follow the setup above you'd be fine in any case.

The other use case could be population of data, e.g., in combination with a global state container:

// Lazy loaders
const TranslatePageView = () => import('./translatepage').then(m => m.default);
const common = () => import('./common');
const prerequest = () => fetch('/somedata')
  .then(res => import('./setstore').then(m => m.default(res)));

// Components
const TranslatePage = app.fromLazy(TranslatePageView, ['common', 'prerequest']);

// Registrations
app.defineDependency('common', common);
app.defineDependency('prerequest', prerequest);
app.registerPage('/translate', TranslatePage);

:::

::: summary: For Piral instance developers

Using lazy loading with Piral is as simple as installing piral-lazy.

import { createLazyApi } from 'piral-lazy';

The integration looks like:

const instance = createInstance({
  // important part
  plugins: [createLazyApi()],
  // ...
});

:::

Piral is released using the MIT license. For more information see the license file.