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

There are a couple of ways to constrain the version for installation.

1. Add lower and upper bounds to package versions in the cabal file like Mikhail mentioned above, example of such a file here

2. Additionally, you can override the settings in the .cabal file with the flag cabal install --constraint="bar-2.1"

To remove a specific version of a package:

• In a sandbox you can unregister a version with cabal sandbox hc-pkg unregister bar-2.1
• Global unregistering can be done with this command outside of sandbox ghc-pkg unregister bar-2.1