`cabal init` may use `common` stanza when choosing "Library and Executable" and version 2.2 or higher.

[kindaro]

Currently, a generated cabal file would look something like this:

cabal-version:       2.4
-- Initial package description 'x2.cabal' generated by 'cabal init'.  For
-- further documentation, see http://haskell.org/cabal/users-guide/

name:                x2
...

library
  -- exposed-modules:
  -- other-modules:
  -- other-extensions:
  build-depends:       base ^>=4.12.0.0
  hs-source-dirs:      src
  default-language:    Haskell2010

executable x2
  main-is:             Main.hs
  -- other-modules:
  -- other-extensions:
  build-depends:       base ^>=4.12.0.0
  hs-source-dirs:      src
  default-language:    Haskell2010

Surely build-depends, hs-source-dirs and default-language could be moved to a common stanza?

[phadej]

Having same for hs-source-dirs for different components is bad practice; we shouldn't generate such cabal files in the first place.

---

Bad practice because if exe depends on lib, GHC will recompile the modules, and not use the compiled library: double compilation of same modules.

[ulysses4ever]

Currently, cabal init does generate a common stanza -- one for ghc-options: -Wall. The stanza is called warnings, so adding anything from the above here would not make sense. And adding more common stanzas in the template may be a bit too much.

That said, default-language does sound like a good candidate for a common stanza. build-depends and hs-source-dirs less so.

Overall, I'm unsure that this ticket needs to stay open since there's an example of common stanza in the template.

[Mikolaj]

The default-language: Haskell2023 is tempting. Perhaps don't call the stanza "warnings", but "basic" or something like that? I'm not sure what culture of writing stanzas we want to promote. E.g., concern separation vs ad hoc bundles of options.

[sullyj3]

FWIW, having common dependencies by default in the project scaffold is one of the trivial conveniences that still keeps me using stack

[gbaz]

I think the comment from @Mikolaj is pretty relevant here. Personally, I like the direct dependencies of my test-suite or executable stanza to be much slimmer than the direct dependencies of the library, where possible. Of course, since the indirect deps will still come from the library, its not an actual win in terms of linking, etc. But it often feels nicer to just have less stuff in scope unless I explicitly intend it to be there. Possibly we should have another option to init to let users pick if they would like a common defaults stanza including language and dependencies, or an option for each even?