Enabling documentation seems to swallow ghc-options passed

[Swordlash]

Describe the bug

Pretty much what is in the title. Enabling documentation seems to swallow additional ghc-options being passed (either on command line or in cabal.project).

To Reproduce
Steps to reproduce the behavior:

cabal-test.cabal:

cabal-version:      3.0
version:            0.1.0
name:               cabal-test
build-type:         Simple

executable cabal-test
    main-is:          Main.hs
    build-depends:    base
    hs-source-dirs:   app
    default-language: Haskell2010

in the app/Main.hs:

module Main where

import Data.List -- note: redundant import
 
main :: IO ()
main = putStrLn "Hello, Haskell!"

Run

$ cabal run  --ghc-options="-Wall -Werror" --enable-documentation

Expected behavior
The build should fail with unused import. Instead, not even a warning is printed.

System information

• Operating system: Linux Ubuntu 22.04 x86_64
• cabal: 3.14.1.1
• ghc: 9.6.6 (tested with 9.8.4 as well)

[chreekat]

I can't reproduce with Cabal 3.12.1.0,

but I do note that cabal run won't recompile if I add --ghc-options after it's already compiled once.

After a clean, the expected error shows up.

[b@kuusi:~/tmp/cabal-10782]$ cabal clean

[b@kuusi:~/tmp/cabal-10782]$ cabal run
Warning: The package list for 'hackage.haskell.org' is 15 days old.
Run 'cabal update' to get the latest list of available packages.
Resolving dependencies...
Build profile: -w ghc-9.6.6 -O1
In order, the following will be built (use -v for more details):
 - cabal-test-0.1.0 (exe:cabal-test) (first run)
Configuring executable 'cabal-test' for cabal-test-0.1.0...
Preprocessing executable 'cabal-test' for cabal-test-0.1.0...
Building executable 'cabal-test' for cabal-test-0.1.0...
[1 of 1] Compiling Main             ( app/Main.hs, /home/b/tmp/cabal-10782/dist-newstyle/build/x86_64-linux/ghc-9.6.6/cabal-test-0.1.0/x/cabal-test/build/cabal-test/cabal-test-tmp/Main.o )
[2 of 2] Linking /home/b/tmp/cabal-10782/dist-newstyle/build/x86_64-linux/ghc-9.6.6/cabal-test-0.1.0/x/cabal-test/build/cabal-test/cabal-test
Hello, Haskell!

[b@kuusi:~/tmp/cabal-10782]$ cabal run --ghc-options="-Wall -Werror" --enable-documentation
Build profile: -w ghc-9.6.6 -O1
In order, the following will be built (use -v for more details):
 - cabal-test-0.1.0 (exe:cabal-test) (configuration changed)
Configuring executable 'cabal-test' for cabal-test-0.1.0...
Preprocessing executable 'cabal-test' for cabal-test-0.1.0...
Building executable 'cabal-test' for cabal-test-0.1.0...
Hello, Haskell!

[b@kuusi:~/tmp/cabal-10782]$ cabal clean

[b@kuusi:~/tmp/cabal-10782]$ cabal run --ghc-options="-Wall -Werror" --enable-documentation
Warning: The package list for 'hackage.haskell.org' is 15 days old.
Run 'cabal update' to get the latest list of available packages.
Resolving dependencies...
Build profile: -w ghc-9.6.6 -O1
In order, the following will be built (use -v for more details):
 - cabal-test-0.1.0 (exe:cabal-test) (first run)
Configuring executable 'cabal-test' for cabal-test-0.1.0...
Preprocessing executable 'cabal-test' for cabal-test-0.1.0...
Building executable 'cabal-test' for cabal-test-0.1.0...
[1 of 1] Compiling Main             ( app/Main.hs, /home/b/tmp/cabal-10782/dist-newstyle/build/x86_64-linux/ghc-9.6.6/cabal-test-0.1.0/x/cabal-test/build/cabal-test/cabal-test-tmp/Main.o )

app/Main.hs:3:1: error: [-Wunused-imports, Werror=unused-imports]
    The import of ‘Data.List’ is redundant
      except perhaps to import instances from ‘Data.List’
    To import instances alone, use: import Data.List()
  |
3 | import Data.List -- note: redundant import
  | ^^^^^^^^^^^^^^^^

[b@kuusi:~/tmp/cabal-10782]$

[jasagredo]

I agree with @chreekat. My understanding is that ghc-options passed via the CLI do not trigger a rebuild in some cases. I don't know whether this is a cabal issue or just that the invocation to GHC with these new flags decides that it doesn't need to recompile the file:

~\cc via λ 9.10.1 took 2s
➜ ghc Main.hs
[1 of 2] Compiling Main             ( Main.hs, Main.o )
[2 of 2] Linking Main.exe

~\cc via λ 9.10.1
➜ ghc -Wall -Werror Main.hs

~\cc via λ 9.10.1
➜ rm -rf Main.o Main.hi Main.exe

~\cc via λ 9.10.1
➜ ghc -Wall -Werror Main.hs
[1 of 2] Compiling Main             ( Main.hs, Main.o )
Main.hs:3:1: error: [GHC-66111] [-Wunused-imports, Werror=unused-imports]
    The import of ‘Data.List’ is redundant
      except perhaps to import instances from ‘Data.List’
    To import instances alone, use: import Data.List()
  |
3 | import Data.List -- note: redundant import
  | ^^^^^^^^^^^^^^^^

This looks like a GHC thing and not a cabal issue.

[Swordlash]

As I mentioned the bug is on 3.14.1.1; I also cannot reproduce it with 3.12.1.

See mlabs-haskell/covenant#39

[jasagredo]

Ok, I checked the cabal verbose output and indeed you are right, I'm sorry. My first immediate guess was that the re-compilation with documentation was not complaining. If we invoke with --enable-documentation it seems we call GHC with these arguments:

Running: "C:\ghcup\bin\ghc.exe" ... "-haddock"

and if I remove --enable-documentation it uses my args defined in my global cabal config as well as the cli args:

Running: "C:\ghcup\bin\ghc.exe" ... "-optc-Wno-pragma-pack" "-optc-Wno-macro-redefined" "-optc-Wno-missing-declarations" "-optl-Wl,--allow-multiple-definition" "-optc-Wno-pragma-pack" "-optc-Wno-macro-redefined" "-optc-Wno-missing-declarations" "-optl-Wl,--allow-multiple-definition" "-Wall" "-Werror"

notice the -Wall and -Werror at the end.

So I think this is a legitimate bug.

[chreekat]

As I mentioned the bug is on 3.14.1.1

Indeed, sorry I was so cryptic: I meant to preclude 3.12 on the one hand (so if it's a bug on 3.14, it's probably only on 3.14), and raise a potential separate confounding issue at the same time.

Sounds like there are two bugs :)

[Mikolaj]

Yay, thank you for reproducing. This is madness.

@chreekat: is the separate issue already reported in our bug tracker? What keywords to use to search for it?

[jasagredo]

Fixed in #10783. However note the comment I made there.