"Silent" (zero exit code) failure with mismatched temporary files

[geekosaur]

I attempted to print-api on haskell/cabal (haskell/cabal#10259) and forgot to clean up the dist directory I use for print-api, which had leftovers from building for print-api on cabal's 3.12.1.0 release. The result was print-api complaining about symbols from 3.12.1.0 and dying, but with a 0 exit code so the Makefile didn't detect the error and copied zero-length output over the old API records.

[Kleidukos]

@geekosaur was it print-api complaining or the GHC API? Do you still have the error message? If no, could you give me a list of steps to reproduce?

[geekosaur]

I'm re-running the reproducer, but it's somewhat complicated: I need to cherry-pick the API checking commit into a fork of cabal's 3.12 branch, run make update-api, then switch back to my local branch for haskell/cabal#10259 and run make generate-api there without removing dist-* first.

The error message is definitely from the GHC API, but I'd hope it would be possible to catch errors from it.

[geekosaur]

ghcup run --ghc 9.10.1 -- print-api --package-name cabal-install-solver | sed 's/\([( ]\)[Cc]abal-[-0-9.][-0-9]*:/\1/g' >cabal-install-solver-9.10.1.api
print-api: <no location info>: error: [GHC-87110]
    Could not load module `Distribution.Client.Utils.Assertion'.
    It is a member of the hidden package `cabal-install-solver-3.12.1.0'.
HasCallStack backtrace:
  finally, called at compiler/GHC/Utils/Panic.hs:303:7 in ghc-9.10.1-69c3:GHC.Utils.Panic


make generate-api  338.85s user 13.88s system 100% cpu 5:50.77 total

Note that (a) it's referencing a symbol from 3.12.1.0, and (b) make believes print-api succeeded. It's not the pipeline that caused it, because failures in a pipeline fail the whole pipeline:

hilfy «crawl:master» Z$ false | cat
zsh: exit 1     false | 
zsh: done       cat

[Kleidukos]

Thank you very much!

[geekosaur]

Hm, I stand corrected, so I may have to edit that pipeline (I think the sed ended up being unnecessary anyway, but see #14).

hilfy «crawl:master» Z$ (false | cat) || echo oops
hilfy «crawl:master» Z$    

[geekosaur]

Okay, yes, it's the pipeline, apparently I'd forgotten that shells don't handle "internal" failures right even in 2024.

hilfy «crawl:master» Z$ {false | cat} && echo oops
zsh: exit 1     false | 
zsh: done       cat
oops
hilfy «crawl:master» Z$ 

Or POSIX requires them to be dumb about it for backward compatibility, or something.

[geekosaur]

Okay, yes, fails properly without the sed. Closing.