`cabal install --lib` on `master` always brings `base` into scope

[sol]

Describe the bug
I just noticed that package environments created with cabal-3.10.2.1 always bring base into scope.

1. Is this a bug, or intentional?
2. If intentional, what is the rational?
3. Is there a way to prevent this, reverting to the cabal-3.10.2.1 behavior?

To Reproduce

$ cabal-3.10.2.1 install --package-env=foo.env --lib relude && cat foo.env

package-db /home/sol/.local/state/cabal/store/ghc-9.8.1/package.db
package-id base-4.19.0.0-c1f2
package-id relude-1.2.1.0-99ccbd1e31593ddccbc7a9d9260492b913d75dae58e3f7684fb550a45d957235

vs

$ cabal-3.10.1.0 install --package-env=foo.env --lib relude && cat foo.env

clear-package-db
global-package-db
package-db /home/sol/.local/state/cabal/store/ghc-9.8.1/package.db
package-id relude-1.2.1.0-99ccbd1e31593ddccbc7a9d9260492b913d75dae58e3f7684fb550a45d957235

[gbaz]

intentional: #8903

ticket with discussion here: #8894

[gbaz]

Is there a reason you don't want base added, btw?

[sol]

Is there a reason you don't want base added, btw?

https://gitlab.haskell.org/ghc/ghc/-/issues/24399

[sol]

Thanks @gbaz.

intentional: #8903

That's unfortunate.

My understanding is that environment files are meant to precisely control the environment (read: what exact packages are in scope).

With 3.10.1.0 I think it was easy to add base explicitly, if desired by the user.

On the other hand, with 3.10.2.1, is there a way to explicitly ask cabal to not add base?

[gbaz]

On the other hand, with 3.10.2.1, is there a way to explicitly ask cabal to not add base?

Unfortunately not. It should be easy enough to remove base by hand, should you so desire, although that's not the most pleasant workflow.

As the linked tickets show, most people want base most of the time, and there was a lot of frustration (only some reflected on the ticket) when this was removed as part of a broader cleanup. (Before, cabal had also added a lot of other stuff too). I imagine a pr for a flag would be welcomed, to add an explicit mechanism for users who want it.

[ulysses4ever]

I was one of those who argued for inclusion of base by default but I find sol's argument convincing now. Can we have the cake and eat it too? There may be two ways forward (besides simply reverting):

• revert the change and think how to guide the users who missed base unintentionally by carefully crafting a new warning;

• leave the change but add a flag like --no-base which doesn't add base.

[tomsmeding]

I vote for the second option (--no-base).

The Haskell ecosystem as a whole largely assumes one uses base. Similarly, it largely assumes that one uses Prelude. For the latter, if you don't want that, we have -XNoImplicitPrelude. Similarly, I would argue that the --no-base option makes the most sense. If you want non-standard behaviour, add a flag; people who want the expected thing should pass fewer flags.

[ulysses4ever]

Totally agree with Tom on this one. Shouldn't be hard to implement.