Add support for source generators in Bloop

[Duhemm]

This commit changes the Bloop project definition to add a new field,
sourceGenerators, which can be used to define source generators.

Source generators are parts of the build that are run when Bloop gathers
the sources of a project (either when queried via BSP or when
compiling).

Source generators are configured with globs matching input files, an
output directory, and a program to run. When the inputs or known outputs
of a source generator change, the source generator is automatically
re-run. When there are no changes, the result of a source generator is
cached.

The command to execute to run a source generator will be built from the
configured argv, followed by the output directory and the input files.

[oyvindberg]

Hey this is exciting! Can you see a path forward to having a source generator being a class file in another bloop project in the same build? that's something I really want

[Duhemm]

Hey this is exciting! Can you see a path forward to having a source generator being a class file in another bloop project in the same build? that's something I really want

Interesting, I hadn't thought of this. I think that this should work for bloop compile in the current implementation, but not when querying the sources in BSP. Actually I guess your source generator could run bloop run my-source-generator -- output-directory input1 input2 ... 🤔

[tgodzik]

@Duhemm This looks great! Is it ready to review?

[Duhemm]

Thanks @tgodzik ! I think it is ready for review. There was an issue where the source generators would not be re-run when their inputs changed in watch mode, that I unfortunately couldn't figure out before going on vacation. It's fixed now!

[tgodzik]

Thanks @tgodzik ! I think it is ready for review. There was an issue where the source generators would not be re-run when their inputs changed in watch mode, that I unfortunately couldn't figure out before going on vacation. It's fixed now!

Ok cool, I am just going on some very short vacations so I will take a look on Monday.

We also merged the update to Monix 3 just right now, so that caused some conflicts unfortunately 😓

But now we should be able to update to Scala 2.13 on the plus side.

[Duhemm]

Thanks for the heads up. I rebased and fixed the conflicts.

[tgodzik]

Looks good! I left a couple of comments, but this seems like a really good approach.

[Duhemm]

I think the test failure is unrelated to this change:

[error] Failed: Total 346, Failed 1, Errors 0, Passed 345
[error] Failed tests:
[error] 	bloop.bsp.LocalBspIntellijClientSpec

[tgodzik]

The error is unrelated, LGTM 🎉

[Duhemm]

Nice, thank you! There's no rush in merging, but in case you were waiting for me to do it, I don't have write permissions to this repository anymore 😄

[tgodzik]

Nice, thank you! There's no rush in merging, but in case you were waiting for me to do it, I don't have write permissions to this repository anymore smile

Ach, ok. I can add you back to the repo if you want?

[Duhemm]

Yes, please, if you don't mind. I can't promise anything, but I'd be happy to help maintain the project.

[tgodzik]

Added!