Currently undecorated classes are intentionally not processed
with ngcc. This is causing unexpected behavior because decorator
handlers such as `base_def.ts` are specifically interested in class
definitions without top-level decorators, so that the base definition
can be generated if there are Angular-specific class members.
In order to ensure that undecorated base-classes work as expected
with Ivy, we need to run the decorator handlers for all top-level
class declarations (not only for those with decorators). This is similar
to when `ngtsc` runs decorator handlers when analyzing source-files.
Resolves FW-1355. Fixes https://github.com/angular/components/issues/16178
PR Close#30821
This commit introduces a new interface, which abstracts access
to the underlying `FileSystem`. There is initially one concrete
implementation, `NodeJsFileSystem`, which is simply wrapping the
`fs` library of NodeJs.
Going forward, we can provide a `MockFileSystem` for test, which
should allow us to stop using `mock-fs` for most of the unit tests.
We could also implement a `CachedFileSystem` that may improve the
performance of ngcc.
PR Close#29643