cabal build -j

[UnkindPartition]

Now that cabal build behaves more like cabal install (it can build several packages if we're in a sandbox), it'd be nice if that could be done in parallel in the same way as with cabal install.

[23Skidoo]

Duplicate of #976.

[UnkindPartition]

I don't think it's a dup. #976 talks about building modules in parallel. This one is more modest — it's about enabling an already implemented mode (building packages in parallel) for a new subcommand (cabal build).

[23Skidoo]

@feuerbach It doesn't really make sense to talk about build and multiple packages since with build you're always only building a single package. Maybe what you have in mind is multiple build components (e.g. building tests and benchmarks in parallel)?

If you're talking about add-source deps, they're implemented by running install before build and should already build in parallel if you enabled that in ~/.cabal/config (just checked - they actually do).

[UnkindPartition]

If you're talking about add-source deps

Yes.

they're implemented by running install before build and should already build in parallel if you enabled that in ~/.cabal/config

Right. But -j is an alternative to enabling parallel builds globally in ~/.cabal/config. And I cannot pass it when cabal install is invoked implicitly by cabal build. So it seems sensible for cabal build to accept a -j option and pass it to the implicit cabal install invocation.

[23Skidoo]

@feuerbach I guess I can do that. For now, build -j will be just "parallel install of add-source deps" and in the future it will enable parallel module-level builds.

[23Skidoo]

Since we're also calling maybeInstallAddSourceDeps in testAction and benchAction, it probably makes sense to add a --jobs argument for them also. I'm a bit reluctant, though.