Hi Nicolas,
Before, I put compiler warning flags like `-Wall` in `Ghc-Options` .. Having these options in `mypackage.cabal` always felt slightly weird, since they are in no way required for a package to function: they're developer options, not user/consumer options.
They'd be certainly out of place in a binary package. However, a source package is meant to be compiled, so instructing the compiler to produce warnings during compilation seems relevant. A related reason is that IIRC haskell-ci does `cabal sdist` and then runs all its operations based on the resulting source package. So, if you want to see warnings in CI logs, you need to retain the relevant instruction in the source package created by `cabal sdist`. And warnings sometimes help to explain why compilation fails or why the resulting binary misbehaves.
If it is, I did run into a couple of issues getting things to actually work. Whilst putting `Ghc-Options` in a `Package mypackage` section in `cabal.project` seems to work, I'm unable to achieve the same resulsts for C compiler invocations. Presumably there's a `Gcc-Options` setting one can use (which is also generated in `cabal.project.local` by `cabal configure --gcc-options ...`). However, in testing, it appears said compiler optons are only passed to GCC when compiling, e.g., a HSC2HS file, but not when compiling a C file part of a `C-Sources` setting (whilst `Cc-Options` in `mypackage.cabal` are).
Is there some discrepancy between what can be done from `cabal.project` vs. `mypackage.cabal`? Is this intentional? Am I trying to accomplish something that isn't/shouldn't be supported by Cabal in the first place?
That sounds like a bug. Is there anything relevant in the issue tracker? All the best, Mikolaj