sbt/main
Ethan Atkins 25e97f99f5 Add custom external hooks
For projects with a large number of files, zinc has to do a lot of work
to determine which source files and binaries have changes since the last
build. In a very simple project with 5000 source files, it takes roughly
750ms to do a no-op compile using the default incremental compiler
options. After this change, it takes about 200ms. Of those 200ms, 50ms
are due to the update task, which does a partial project resolution*.

The implementation is straightforward since zinc already provides an api
for overriding the built in change detection strategy. In a previous
commit, I updated the sources task to return StampedFile rather than
regular java.io.File instances. To compute all of the source file
stamps, we simply list the sources and if the source is in fact an
instance of StampedFile, we don't need to compute it, otherwise we
generate a StampedFile on the fly. After building a map of stamped files
for both the sources files and all of the binary dependencies, we simply
diff these maps with the previous results in the changedSources,
changedBinaries and removedProducts methods.

The new ExternalHooks are easily disabled by setting
`externalHooks := _ => None`
in the project build.

In the future, I could see moving ExternalHooks into the zinc project so
that other tools like bloop or mill could use them.

* I think this delay could be eliminated by caching the UpdateResult so
long as the project doesn't depend on any snapshot libraries. For a
project with a single source, the no-op compile takes O(50ms) so caching
the project resolution would make compilation start nearly
instantaneous.
2018-10-09 12:09:42 -07:00
..
src Add custom external hooks 2018-10-09 12:09:42 -07:00
NOTICE Add, configure & enforce file headers 2017-10-05 09:03:40 +01:00