Some tools (such as Language Server and ng-packagr) only care about
the processed typings generated by ngcc. Forcing these tools to process
the JavaScript files as well has two disadvantages:
First, unnecessary work is being done, which is time consuming.
But more importantly, it is not always possible to know how the final bundling
tools will want the processed JavaScript to be configured. For example,
the CLI would prefer the `--create-ivy-entry-points` option but this would
break non-CLI build tooling.
This commit adds a new option (`--typings-only` on the command line, and
`typingsOnly` via programmatic API) that instructs ngcc to only render changes
to the typings files for the entry-points that it finds, and not to write any
JavaScript files.
In order to process the typings, a JavaScript format will need to be analysed, but
it will not be rendered to disk. When using this option, it is best to offer ngcc a
wide range of possible JavaScript formats to choose from, and it will use the
first format that it finds. Ideally you would configure it to try the `ES2015` FESM
format first, since this will be the most performant.
Fixes#40969
PR Close#40976
Later when we implement the ability to continue processing when tasks have
failed to compile, we will also need to avoid processing tasks that depend
upon the failed task.
This refactoring exposes this list of dependent tasks in a way that can be
used to skip processing of tasks that depend upon a failed task.
It also changes the blocking model of the parallel mode of operation so
that non-typings tasks are now blocked on their corresponding typings task.
Previously the non-typings tasks could be triggered to run in parallel to
the typings task, since they do not have a hard dependency on each other,
but this made it difficult to skip task correctly if the typings task failed,
since it was possible that a non-typings task was already in flight when
the typings task failed. The result of this is a small potential degradation
of performance in async parallel processing mode, in the rare cases that
there were not enough unblocked tasks to make use of all the available
workers.
PR Close#36083
