Provide extension points in order to add custom behavior to the service worker file generated by the angular cli.

[balteo]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[x] Feature request
[x] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/angular/angular/blob/master/CONTRIBUTING.md#question

Current behavior

As of now, I can either register the angular-generated service worker (i.e. /ngsw-worker.js) or register my own custom service worker (see documentation: https://angular.io/api/service-worker/ServiceWorkerModule#static-members)

Expected behavior

One should be able to add custom behavior to angular-generated service workers (i.e. /ngsw-worker.js). For instance what if I want to add business logic to the service worker. It would be nice to provide extension points in order to achieve this and document them.

EDIT (gkalpak): Other related issues/issues that could be fixed by this: #24387, #26413, #30195, #46984

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[yelhouti]

@jessicajaniuk thanks for marking this as under consideration, I would like to work on this to move it forward, I was thinking about integrating it with workbox, to avoid redundant work, there mechanism of registerRoute seems very well suited for this use case. And their code could be executed after checking dataGroups in:

angular/packages/service-worker/worker/src/app-version.ts

Line 183 in 22871e9

if (this.adapter.normalizeUrl(req.url) !== this.indexUrl && this.isNavigationRequest(req)) {

It can even, IMO, replace the dataGroup implementation since AFAICT dataGroup is one of the uses cases covered by the caching startegies of workbox.

Also, once workbox is integrated, customisations could be as simple multiple calls of registerRoute in files referenced in angular.json

Other entrypoint can also be added later for uses cases that different from handling fetch events.