cabal repl should turn on the default extensions

[dmwit]

If I specify default-extensions in my cabal file, that's likely because those are frequently needed (or wanted) when playing with things in that component. Since the primary thing you do in cabal repl is play with things in a component, you tend to frequently want those same extensions turned on in the ghci session (or at least, I tend to frequently want that). I can turn them on myself, of course, as I discover I need them, but it would be nice for cabal to do it for me.

[jneira]

Hi, thanks for the proposal which at a first glance makes sense. One possible workaround is set the extensions in a ghci specific config file (~/.ghc/ghci.conf, ./.ghci) to not have to set them manually, but you still have to duplicate them in two places
Issues related: #7696 and the issues linked there

[jneira]

Hi again, what versions of ghc and cabal are you using? It seems it works for me with cabal-3.8.1.0 and ghc-8.10.7

I've added in my cabal-test.cabal, in an executable stanza, default-extensions: LambdaCase, OverloadedStrings
And then i've run cabal repl -v to have more verbose output:

PS D:\dev\ws\haskell\cabal-test> cabal repl cabal-test:exe:cabal-test -v
...
"D:\ghcup\bin\ghc.exe" "--interactive" "-fbuilding-cabal-package" "-O0" "-outputdir" "D:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\cabal-test\cabal-test-tmp" "-odir" "D:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\cabal-test\cabal-test-tmp" "-hidir" "D:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\cabal-test\cabal-test-tmp" "-stubdir" "D:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\cabal-test\cabal-test-tmp" "-i" "-iD:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\cabal-test\cabal-test-tmp" "-icommon-src" "-iapp" "-iD:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\cabal-test\autogen" "-iD:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\global-autogen" "-ID:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\cabal-test\autogen" "-ID:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\global-autogen" "-ID:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\cabal-test\cabal-test-tmp" "-ID:\ghcup\msys64\mingw64\include" "-optP-include" "-optPD:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\build\cabal-test\autogen\cabal_macros.h" "-LD:\ghcup\msys64\mingw64\lib" "-hide-all-packages" "-Wmissing-home-modules" "-no-user-package-db" "-package-db" "D:\cabal\store\ghc-8.10.7\package.db" "-package-db" "D:\dev\ws\haskell\cabal-test\dist-newstyle\packagedb\ghc-8.10.7" "-package-db" "D:\dev\ws\haskell\cabal-test\dist-newstyle\build\x86_64-windows\ghc-8.10.7\cabal-test-0.1.0.0\x\cabal-test\package.conf.inplace" "-package-id" "base-4.14.3.0" "-package-id" "bytestring-0.10.12.0" "-package-id" "cabal-test-0.1.0.0-inplace" "-XHaskell2010" "-XLambdaCase" "-XOverloadedStrings" "app\Main.hs" "MyExe.MyModule" "MyExe.MyPrefix.MyModule2" "-hide-all-packages"
GHCi, version 8.10.7: https://www.haskell.org/ghc/  :? for help
[1 of 3] Compiling MyExe.MyModule   ( app\MyExe\MyModule.hs, interpreted )
[2 of 3] Compiling Main             ( app\Main.hs, interpreted )
[3 of 3] Compiling MyExe.MyPrefix.MyModule2 ( app\MyExe\MyPrefix\MyModule2.hs, interpreted )
Ok, three modules loaded.
*Main> "hi" :: BS.ByteString
"hi"
*Main>

Observe that the ghc --interactive final invocation includes the default-extensions of the cabal file.

Could you share the output of cabal repl target -v?

[Mikolaj]

@dmwit: ping?

[dmwit]

Not sure which project I was having this problem on. Seems to be working now on the one I thought most likely to be the culprit, so I guess better close as not reproducible.