Is there any way to define flags for cabal dependencies?

Question

I recently ran into a Cabal issue that I only managed to solve by manually installing transformers-compat with the -f transformers3 flag in my cabal sandbox be

Answer 1

Newer versions of Cabal let you specify constraints in your cabal.project.local or cabal.project file. For example:

constraints: hmatrix +openblas

Is there any way to indicate in my application's .cabal file that I depend on a library so that it is built with the specific build flag?

No, but in your case this is not actually a problem in the solver and is rather and uninformative error (caused by someone's less than judicious uses of flags).