Fixes angular/angular#31256.

When differential loading is used, by default the Angular Service Worker will double-(pre)fetch the ES5 & ES2015 bundles, unless those are explicitly excluded as per angular/angular#31256 (comment).

Excluding those ES5 bundles from the ngsw-config.json template would provide a better developer experience, removing the risk of double fetching the JS bundles when differential loading is used/enabled, while having no impact when differential loading isn't used.

Doing so would prevent browsers with Service Worker support but without <script type="module"> support to prefect the correct JS bundles, but I'd argue the tradeoff is acceptable (and the default ngsw-config.json config can just be modified) compared to current double fetching.

In addition:

• the few browser versions that support Service Workers but not <script type="module">, which according to https://caniuse.com/#feat=es6-module & https://caniuse.com/#feat=serviceworkers are basically Firefox < 60 (current is 76), Chrome < 61 (current is 83), Opera < 48 (current is 68), are all outside Angular's browser support ranges (and outdated).
• the Angular Service Worker has also no support to load a different (es5) ngsw.json config for these browsers (nor the Angular CLI has support to built it), and realistically will never need to.

This is definitely a step in the right direction.

It would be even better imo if we could adapt the ngsw-config.json template to the TS config target. Is it possible to do that, @alan-agius4?

It would be even better imo if we could adapt the ngsw-config.json template to the TS config target. Is it possible to do that, @alan-agius4?

One downside of doing so is that in my case I enabled the Angular Service Worker (and applied the @angular/service-worker schematic) before turning differential loading on, i.e. before bumping the TS config target.

Also I believe that the Angular CLI is now setting the target to es2015 by default (and enabling differential loading), so there might not be a strong use case for using the TS config target, especially as excluding /*-es5*.js has no effect when the target is set to es5, since then the JS bundle names don't have the -es5/-es2015 suffixes.