pr-9464

synopsis: Support per-component builds when coverage is enabled
packages: Cabal cabal-install
prs: #9464
issues: #4798 #5213 #6440 #6397
significance: significant

description: {

Cabal now supports per-component builds when coverage is enabled.  This enables
coverage for packages with internal libraries (#6440), and enables coverage for
packages that use backpack (#6397), even though we do not get coverage for
instantiations of an indefinite module (it is not clear what it means for HPC
to support backpack, regardless of Cabal).

To achieve this, hpc information (`.mix` files) from a library is now written
into the package database of a library under `extraCompilationArtifacts`.

Cabal configure (via the Setup interface) now accepts --coverage-for=<unit-id>,
a flag which specifies which libraries should be included in the coverage
report for some testsuite.

}