New Bazel output stream available for testing

[Klaus Aehlig]

Hello everybody,

we're planning to, in the long run, switch to a new output stream for
Bazel. The main aim is to provide a better insight in the progress bar
into what bazel is currently doing. Everybody is very welcome to test
it; it can be enabled by adding --experimental_ui to your build or test
invocation. To make this change permanent add 'build --experimental_ui'
to your .bazelrc file.

Known issues.
- Progress reporting is not implemented for LegacyLoadingPhaseRunner,
so progress updates during loading and analysis phase are
only available if the --experimental_skyframe_target_pattern_evaluator
option is given as well.
- Fix 4c827b50b24acf did not make it into the 0.3.0 release, so
--experimental_show_artifacts does not work properly with --experimental_ui
on 0.3.0 (thus breaking IDE support). If you want to try --experimental_ui
with an IDE please use Bazel from head, or cherry-pick the mentioned
commit.

Any feedback is very welcome.

Thanks,
Klaus


--
Klaus Aehlig
Google Germany GmbH, Erika-Mann-Str. 33, 80636 Muenchen
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
Geschaeftsfuehrer: Matthew Scott Sucherman, Paul Terence Manicle

[Erik Kuefler]

I like it a lot. In the past I'd used --progress_report_interval=1 to get a similar effect, this is snappier and cleaner.

Is there a way to control the number of simultaneous actions that it will print? Right now it appears to show up to 3 actions and elides the rest, which doesn't give much room to see everything that's going on.

On the subject of making Bazel's output cleaner, I also just filed a feature request at https://github.com/bazelbuild/bazel/issues/1405 to clean up spam from javac, which has been annoying me since Bazel first launched.

[Klaus Aehlig]

> Is there a way to control the number of simultaneous actions that it will
> print?

Not yet, but it is easy to add.

> Right now it appears to show up to 3 actions and elides the rest,
> which doesn't give much room to see everything that's going on.

While I'm happy to make the number 3 configurable, I think we can't
avoid hiding some of the concurrent actions---having 200 parallel actions
is not uncommon (e.g., when building bazel), whereas my terminal has
only 65 lines.

> On the subject of making Bazel's output cleaner, I also just filed a
> feature request at https://github.com/bazelbuild/bazel/issues/1405 to clean
> up spam from javac, which has been annoying me since Bazel first launched.

I've seen that issue, but it might be hard to act upon, as it requires
some understanding of the output of the javac. (As the javac can also
report useful warnings.)