BuildReports don't seem to work with v2-build

[gbaz]

A more focused follow-up to #6811

After some digging, it appears that the --build-summary (and --build-log?) flags when passed to new-build are no-ops. I looked through the code, and it seems to me the issue is that this info goes into the installSummaryFile config field, but the only place that (or the BuildReports) module is used is in Distribution.Client.Install such as here:

cabal/cabal-install/Distribution/Client/Install.hs

Line 824 in 06c3eff

let buildReports = BuildReports.fromInstallPlan platform (compilerId comp)

So v1-build didn't do this, only v1-install. Furthermore, v2-build, if I understand the system (and by implication v2-install) won't hit that path either.

It looks like we'd need to implement similar logic in ProjectOrchestration.hs if we want to make use of this? (https://github.com/haskell/cabal/blob/10f33badad67a471d8635e288d24fa495db7d504/cabal-install/Distribution/Client/ProjectOrchestration.hs)

Note that this is actually pretty important for GSoC work, because we can't move the docbuilder to v2-build if we don't have build reports as part of it.

Can someone confirm that this analysis makes sense?

[gbaz]

Btw, @hvr do the matrix builders just not make use of build-reports, or am I missing something here?

[phadej]

Can someone confirm that this analysis makes sense?

Yes.

FWIW, for docbuilder the #6876 will need to be tacked too (and I don't have good ideas how to do that, rebuilding everything is lame - at least by default).

[gbaz]

i was also just pointed to the fact that we may have multiple per-component build-reports, so we need to handle that case too. Perhaps extending the build-report syntax to cover multiple packages?