cabal get is confused if the package you want to get was add-source'd to a sandbox

[ezyang]

Steps to reproduce:

ezyang@sabre:~/Dev/labs/cabal-constraint-solver-repro$ ./repro
Unpacking to SHA-1.6.4.2/
Writing a default package environment file to
/srv/code/labs/cabal-constraint-solver-repro/cabal.sandbox.config
Creating a new sandbox at
/srv/code/labs/cabal-constraint-solver-repro/.cabal-sandbox
ezyang@sabre:~/Dev/labs/cabal-constraint-solver-repro$ ./repro
Distribution.Client.Get.unpack: the impossible happened.
CallStack (from HasCallStack):
error, called at Distribution/Client/Get.hs:140:13 in
main:Distribution.Client.Get
ezyang@sabre:~/Dev/labs/cabal-constraint-solver-repro$ cat repro
#!/bin/sh
set -e
cabal get SHA-1.6.4.2
cabal sandbox init

cabal sandbox add-source SHA-1.6.4.2

I'm not going to fix this but I thought I'd put a note.

[omefire]

Is this a regression ?
With cabal@1.22, this doesn't seem to show up:

omefire@omefire-ubuntu:~/Projects/cabal/Bug_3795$ ./repro
cabal: The directory "SHA-1.6.4.2/" already exists, not unpacking.
omefire@omefire-ubuntu:~/Projects/cabal/Bug_3795$ cabal --version
cabal-install version 1.22.6.0
using version 1.22.5.0 of the Cabal library 
omefire@omefire-ubuntu:~/Projects/cabal/Bug_3795$

[ezyang]

Yep, confirmed doesn't repro for cabal-install 1.22, but does repro on 1.24 and HEAD. @omefire, are you interested in diagnosing some more?

[omefire]

Ok, I think this seems like a good bug for me to tackle and get my feet wet with the project. I'll assign it to myself.

[omefire]

Hmm, can't assign it to myself though ...

[ezyang]

If you accept the invite you should be able to assign yourself then.

Since we don't know what is causing the bug it may be annoying to fix. One way to diagnose is to bisect between 1.22 and 1.24 and find the offending commit.

[omefire]

Yep, will do so.

[omefire]

It seems like this issue has been fixed in master.
I can't repro it anymore after getting the latest:

omefire@omefire-ubuntu:~/Projects/cabal/Bug_3795$ /home/omefire/Projects/cabal/dist-newstyle/build/cabal-install-1.25.0.0/build/cabal/cabal get SHA-1.6.4.2
unpacKage
cabal: The directory "SHA-1.6.4.2/" already exists, not unpacking.

[omefire]

Closing it ...