Which cabal packages aren't being used

Question

If I crank up the warnings with GHC, it will warn me which imports aren't being used....

Is there a similar command to tell me which build-depends aren't being used in my <project>.cabal file?

Answer 1

packunused is a simple CLI tool allows to find out which of the packages listed as build-depends in a Cabal package description file are redundant.

You have to build your project with -ddump-minimal-imports then run packunused:

cabal build --ghc-option=-ddump-minimal-imports
packunused

It will print a list of package dependencies that seem to be unused.