cabal run fails on windows due to the long path issue

[ulysses4ever]

Describe the bug
Copied from IRC:

maerwald:
windows cabal test consistently fails: https://github.com/haskell/ghcup-metadata/actions/runs/4396989936/jobs/7699817403#step:3:14665

the same test works with 3.6.2.0: https://github.com/haskell/ghcup-metadata/actions/runs/4397003656/jobs/7699838528

D:\a_temp\foobarbaz\ghcup\ghc\9.4.4\lib../mingw/bin/llvm-ar.exe: error: C:\cabal\script-builds\ff17c4bce8853274ef8c5beb95175084fb96425f714475e54f50bdf49f3b33c6\dist-newstyle\build\x86_64-windows\ghc-9.4.4\fake-package-0\x\cabal-script-main.hs\build\cabal-script-main.hs\cabal-script-main.hs-tmp\Main.p_o.tmp: No such file or directory

yes, there's a regression with long paths on windows

Artem:
any way to check if it works with 3.8.1.0? or how to repro it in general? 'Cause it seems like it cabal runs print $ 1+1, which 3.10 is definitely capable of (even on Windows!). Do I just put the script in a folder with a long path (like above)?

maerwald:
just make sure you don't have CABAL_DIR set and it should reproduce

To Reproduce

No idea.

System information

• Operating system: Windows
• cabal, ghc versions: 3.10.1.0, 9.4.4

[gbaz]

Note that @hasufell considers this a blocker to making cabal-install 3.10.1.0 a recommended release

[jneira]

Thanks for the report, to delimite the scope of the bug:

• it seems to affect only cabal run, at least not cabal build in my tests
• as commented setting CABAL_DIR to a short path workarounds the issue. Another one could be the usual one: enable long paths on windows (i've not tested it though)
• it likely was introduced by the cabal run/script improvements in cabal-3.8 so it is not a regression only for 3.10:

PS D:\dev\ws\haskell\cabal-test> cabal-3.8.1.0.exe .\script.hs
realgcc.exe: error: C:\Users\atrey\AppData\Roaming\cabal\script-builds\8451f75c9bb9fd520bd934aea714d2e240d258f1e884c03cde6784c44c03d9ce\dist-newstyle\build\x86_64-windows\ghc-8.10.7\fake-package-0\x\cabal-script-script.hs\build\cabal-script-script.hs\cabal-script-script.hs-tmp\Main.o: No such file or directory
`gcc.exe' failed in phase `Linker'. (Exit code: 1)
PS D:\dev\ws\haskell\cabal-test>

[ulysses4ever]

Very interesting and useful, thank you, @jneira !

For the future: am I understanding correctly that it's impossible to test in our test suite because we have CABAL_DIR set.

[jneira]

Very interesting and useful, thank you, @jneira !

For the future: am I understanding correctly that it's impossible to test in our test suite because we have CABAL_DIR set.

To be precise the fact which causes the bug is to set CABAL_DIR to a enough long path. It turns out that the default one is long enough to do it.

So setting CABAL_DIR to a long enough path should reproduce the bug. It could be done globally or specifically for a dedicated test

[ulysses4ever]

it likely was introduced by the cabal run/script improvements in cabal-3.8

Maybe page in @bacchanalia in that case