`cabal init` crashes if `git` is not installed

[noiioiu]

Describe the bug
Running cabal init without git installed results in the following error:

git: readCreateProcessWithExitCode: execvp: does not exist (No such file or directory)

or

git: readCreateProcessWithExitCode: posix_spawnp: does not exist (No such file or directory)

To Reproduce
Run cabal init in an empty directory on a system without git installed or after setting $PATH to something that includes cabal and ghc but not git. Answer the prompts; the program will exit with the above error message after you choose a license.

Expected behavior
cabal init should continue running and ask for author name, email address, etc.

System information

• cabal 3.10.3.0, ghc 9.6.5 on NixOs 24.05
• cabal 3.12.1.0, ghc 9.6.6 on OpenBSD 7.6-current

Additional context
The function Distribution.Client.Init.NonInteractive.Heuristics.guessGitInfo uses readProcessWithExitCode, which throws an IOError which should be caught if the file is not found.

[geekosaur]

Huh. Supposedly this was fixed (#8478) unless I'm misreading.

[noiioiu]

No, it looks like the 'fix' only deals with the case where git fails.

readProcessWithExitCode only returns an ExitFailure if git runs and exits unsuccessfully. If git is not found at all, it throws an exception, which causes cabal to exit.

This should be easy to fix, it just requires catching the exceptions and returning Nothing.

[ffaf1]

@BasLaa will be able to diagnose quicker.

[noiioiu]

I have a draft pull request that might fix this.

[ulysses4ever]

Huh. Supposedly this was fixed (#8478) unless I'm misreading.

Haven't check in the code, but the catch maybe that #8478 talks about the non-interactive mode whereas this ticket is about interactive. Unfortunately, since at least the last init rewrite (it happened a couple of years ago), the two modes have very little code in common (in comparison to what one might expect).

[geekosaur]

I was misreading: that ticket fixed it when git was found but not configured. This one's about when git isn't found at all.

[ulysses4ever]

Did you read the description of #8478?

[ulysses4ever]

Maybe you're saying: #8755 didn't fix #8478 even though it claims that. That's sad but not surprising 'cause we didn't have a real integration test in #8755. We should do better this time around.