Ngcc adds properties to the `package.json` files of the entry-points it
processes to mark them as processed for a format and point to the
created Ivy entry-points (in case of `--create-ivy-entry-points`). When
running ngcc in parallel mode (which is the default for the standalone
ngcc command), multiple formats can be processed simultaneously for the
same entry-point and the order of completion is not deterministic.
Previously, ngcc would append new properties at the end of the target
object in `package.json` as soon as the format processing was completed.
As a result, the order of properties in the resulting `package.json`
(when processing multiple formats for an entry-point in parallel) was
not deterministic. For tools that use file hashes for caching purposes
(such as Bazel), this lead to a high probability of cache misses.
This commit fixes the problem by ensuring that the position of
properties added to `package.json` files is deterministic and
independent of the order in which each format is processed.
Jira issue: [FW-1801](https://angular-team.atlassian.net/browse/FW-1801)
Fixes#34635
PR Close#34870
Previously, it was possible for multiple instance of ngcc to be running
at the same time, but this is not supported and can cause confusing and
flakey errors at build time.
Now, only one instance of ngcc can run at a time. If a second instance
tries to execute it fails with an appropriate error message.
See https://github.com/angular/angular/issues/32431#issuecomment-571825781
PR Close#34722
`ngcc` supports both synchronous and asynchronous execution. The default
mode when using `ngcc` programmatically (which is how `@angular/cli` is
using it) is synchronous. When running `ngcc` from the command line
(i.e. via the `ivy-ngcc` script), it runs in async mode.
Previously, the work would be executed in the same way in both modes.
This commit improves the performance of `ngcc` in async mode by
processing tasks in parallel on multiple processes. It uses the Node.js
built-in [`cluster` module](https://nodejs.org/api/cluster.html) to
launch a cluster of Node.js processes and take advantage of multi-core
systems.
Preliminary comparisons indicate a 1.8x to 2.6x speed improvement when
processing the angular.io app (apparently depending on the OS, number of
available cores, system load, etc.). Further investigation is needed to
better understand these numbers and identify potential areas of
improvement.
Inspired by/Based on @alxhub's prototype: alxhub/angular@cb631bdb1
Original design doc: https://hackmd.io/uYG9CJrFQZ-6FtKqpnYJAA?view
Jira issue: [FW-1460](https://angular-team.atlassian.net/browse/FW-1460)
PR Close#32427
This commit adds a new `TaskQueue` implementation that supports
executing multiple tasks in parallel (while respecting interdependencies
between them).
This new implementation is currently not used, thus the behavior of
`ngcc` is not affected by this change. The parallel `TaskQueue` will be
used in a subsequent commit that will introduce parallel task execution.
PR Close#32427
This change does not alter the current behavior, but makes it easier to
introduce `TaskQueue`s implementing different task selection algorithms,
for example to support executing multiple tasks in parallel (while
respecting interdependencies between them).
Inspired by/Based on @alxhub's prototype: alxhub/angular@cb631bdb1
PR Close#32427
George Kalpakas
Pete Bacon Darwin