cabal update creates dist-newstyle folder in $PWD

[Mistuke]

Describe the bug
When cabal update is run this creates a new folder dist-newstyle in PWD.
This seems wrong as the command shouldn't pollute my PWD and will also
fail if ran in a read-only directory

To Reproduce
Steps to reproduce the behavior:

PS C:\Users\WDAGUtilityAccount\Desktop> mkdir temp

    Directory: C:\Users\WDAGUtilityAccount\Desktop

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----        11/13/2022   9:51 PM                temp


PS C:\Users\WDAGUtilityAccount\Desktop> cd .\temp\
PS C:\Users\WDAGUtilityAccount\Desktop\temp> cabal v2-update
Downloading the latest package list from hackage.haskell.org
Package list of hackage.haskell.org is up to date.
The index-state is set to 2022-11-13T17:52:14Z.
PS C:\Users\WDAGUtilityAccount\Desktop\temp> ls


    Directory: C:\Users\WDAGUtilityAccount\Desktop\temp


Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----        11/13/2022   9:51 PM                dist-newstyle

Expected behavior
I don't expect this folder to be created. cabal update updates global state, so I don't understand the need for local storage.

System information

• Operating system: Windows 11
• cabal 3.8.1.0

[ulysses4ever]

cabal repl -b suffers similarly: #8550

[gbaz]

expect this may be fixed by #8358 ?

[ulysses4ever]

expect this may be fixed by #8358?

No. See #8550 for discussion.

[arrowd]

I hope this will end up in the next 3.8 release.

[Mikolaj]

@arrowd: 3.10 branch is about to be cut and this is intended to make it there. Unlikely to make it into a future 3.8 release, if any. (cc @andreasabel)

[juhp]

Worthy of a backport I would say - it's a pretty bad 3.8 regression

Looks like it is non-trivial though (ie #8627 doesn't apply to 3.8)

[gbaz]

the combination of #8358 and #8627 should prevent the creation of dist-newstyle in a directory with no package or project. In the case you run cabal update and there is a package, then dist-newstyle is still created, but I think this is fine.

That said, I do not think we have further plans for a new 3.8 release, so I'm not sure of what the purpose of a backport would be...

[juhp]

I created a backport intended for Fedora 39, which seems to work

[juhp]

That said, I do not think we have further plans for a new 3.8 release,

As I expected ;-(

so I'm not sure of what the purpose of a backport would be...

It is easier to pick commits from a stable branch than hunting around the project and then backporting...

There are quite a few distros shipping 3.8 currently...

[gbaz]

In that case, I think a backport to the 3.8 branch would be welcome.

[juhp]

Let me try then - anyway thanks #8358 and #8627 together indeed apply (my patch above basically just added the minimum from 8358)