Print a warning when assertions are enabled

[jneira]

• Fixes Print a warning when cabal is built with assertions enabled #4377.
• Superseeds Print a warning when assertions are enabled. #4552

I want to remember sometimes cabal builds with assetions enabled were leaked to final users.
Anyways i think warn about it would be useful for the reasons noted in #4377

Not sure how could this be tested without build a cabal version with assertions enabled and not sure it it worths it

---

Please include the following checklist in your PR:

• Patches conform to the coding conventions.
• Any changes that could be relevant to users have been recorded in the changelog.

Please also shortly describe how you tested your change. Bonus points for added tests!

[Mikolaj]

Ideally, we'd distribute alpha versions with a subset of assertions enabled (and enable them for dev builds by default, which probably means all builds from repo source --- do we do that already?), but that would require more than DEBUG_EXPENSIVE_ASSERTIONS, because we'd need to exclude nice-to-have assertions and include only OMG-wrong-results-will-now-silently-be-emitted.

[jneira]

The expensive assertions message is not printed cause the flag and the cpp was moved to cabal-solver after the original pr.
Now i am not sure if it worths to add again them to cabal-install only to be more precise about the message,
Maybe the warning about assertions is enough.
thougts?

[Mikolaj]

I'd find the more precise warning helpful, but then I'm an assertions aficionado.

[jneira]

Specific warning restored:

PS D:\dev\ws\haskell\cabal> cabal build cabal-install --ghc-options=-fno-ignore-asserts -f+debug-expensive-assertions --disable-tests
....
PS D:\dev\ws\haskell\cabal> iex "$(cabal list-bin cabal-install) --version"
Warning: this is a debug build with expensive assertions enabled. This will negatively affect executable performance.
cabal-install version 3.9
compiled using version 3.9.0.0 of the Cabal library

[jneira]

@grayjay respectful ping, I think you could be interested in

[grayjay]

Thanks for updating #4552!

[grayjay]

I'm not sure I understand the purpose of this flag. It looks like it is independent of the one in the solver package, so the warning in this PR doesn't indicate whether the slow functions in the solver are enabled. I don't think that there is a way to make the cabal-install and solver packages share one CPP option, so Main.hs would probably need to call expensiveAssert directly and check for an exception, similarly to how it calls assert.

I also think that it would be fine to leave out the warning about expensive assertions, because they are difficult to enable unintentionally. When I added the flag in #4346, I only intended for it to be enabled in one CI job, in order to check the assertions in tests. I think that the expensive assertions are slow enough that developers wouldn't want to enable them regularly when solving for install plans involving Hackage.

[Mikolaj]

Oh, the cabal flag must have been split when cabal-install and cabal-install-solver had been split. I guess we (may in the future) use the flag in both, but we should treat them separately, alas.

[Mikolaj]

But, as @jneira remarks, using the flag and warning about the flag is a different thing, so I'm OK with simplifying.

[grayjay]

s/us/use/

[jneira]

hmm I thought if the flag name matches all local packages would be parametrized by
but agree the pr will be cleaner without the expensive part so if you think it does not worth it I will remove

[grayjay]

hmm I thought if the flag name matches all local packages would be parametrized by

The flags can be specified independently, as in cabal build cabal --constraint=cabal-install+debug-expensive-assertions.

but agree the pr will be cleaner without the expensive part so if you think it does not worth it I will remove

I think it is much more important to warn about enabling regular assertions, because they are useful in more situations, and it is easier to enable them accidentally. Additionally, even if you revert the part that handles expensive assertions, there will still be a warning whenever they are enabled, since they also require regular assertions to be enabled.

[jneira]

@Mikolaj @grayjay As discussed, i've restored the version which only warns about assertions enabled

[Mikolaj]

This is fine.

[grayjay]

Thanks!

[andreasabel]

Warning updated by

• Clarify assertionsEnabledMsg #8290