Angular contains an NgModule registry, which allows a user to declare
NgModules with string ids and retrieve them via those ids, using the
`getNgModuleById` API.
Previously, we attempted to structure this registration in a clever fashion
to allow for tree-shaking of registered NgModules (that is, those with ids).
This sort of worked due to the accidental alignment of behaviors from the
different tree-shakers involved. However, this trick relies on the
generation of `.ngfactory` files and how they're specifically processed in
various bundling scenarios. We intend to remove `.ngfactory` files, hence
we can no longer rely on them in this way.
The correct solution here is to recognize that `@NgModule({id})` is
inherently declaring a global side-effect, and such classes should not
really be eligible for tree-shaking in the first place. This commit removes
all the old registration machinery, and standardizes on generating a side-
effectful call to `registerNgModuleType` for NgModules that have ids.
There is some risk here that NgModules with unnecessary `id`s may not
tree-shake as a result of this change, whereas they would have in previous
circumstances. The fix here should be to remove the `id` if it's not needed.
Specifying an `id` is a request that the NgModule be retained regardless of
any other references, in case it is later looked up by string id.
PR Close#45024
27b4af7240