Stack fails to build "mutually recursive" packages

[mitchellwrosen]

General summary/comments (optional)

I have a two-package project, where the library in package two depends on the library in package one.

However, there's also an executable component in package one that depends on library two. For some reason, plan construction fails, even when I try to build single components.

Steps to reproduce

1. git clone git@github.com:mitchellwrosen/stack-issue-1.git
2. stack build

Expected

Build succeeds

Actual

Build fails with:

While constructing the build plan, the following exceptions were encountered:



Plan construction failed.

Stack version

Version 1.2.1, Git revision 8ebadf3 (dirty) (4086 commits) x86_64 hpack-0.14.1

Method of installation

Built from source

[mitchellwrosen]

Just following up on this - is it a bug, or working as intended?

[mgsloan]

Thanks a bunch for the report and repro! We do intend to support this usecase, not sure why it isn't working.

[mitchellwrosen]

No problem, and to clarify, is it actually a cycle that can't be built by
cabal? I wasn't sure - it's not actually two components that depend on each
other

On Sep 29, 2016 7:00 PM, "Michael Sloan" notifications@github.com wrote:

This is not intended, it's a result of some cleanups to how the output is
presented. Looks like we aren't detecting cycles correctly. Thanks a bunch
for the report and repro!

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[mgsloan]

Hey @mitchellwrosen, sorry for the delay! I have committed a fix to the error reporting. Now the output looks like

However, you are correct that this case is intended to work fine with stack. I wrote the code involved, and intended to address the problem soon. Marking it as a P1 bug. Thanks so much for the report and repro!

[mitchellwrosen]

Nice error message, and thanks!

[mgsloan]

We actually only support such cycles for test-suites and benchmarks. I believe this is a limitation of the Cabal library, but I'm not 100% sure what limitations we'd run into.

If I try using cabal-install, I get

mgsloan@computer:~/fpco/test-stack/stack-issue-1$ cabal install one/ two/
Warning: The package list for 'hackage.haskell.org' is 193.2 days old.
Run 'cabal update' to get the latest list of available packages.
Resolving dependencies...
cabal: internal error: could not construct a valid install plan.
The proposed (invalid) plan contained the following problems:
The following packages are involved in a dependency cycle one-0.0.0, two-0.0.0
Proposed plan:
Configured one-0.0.0 (.fake.one-0.0.0)
Configured two-0.0.0 (.fake.two-0.0.0)
PreExisting base-4.9.0.0 (base-4.9.0.0)
PreExisting ghc-prim-0.5.0.0 (ghc-prim-0.5.0.0)
PreExisting integer-gmp-1.0.0.1 (integer-gmp-1.0.0.1)
PreExisting rts-1.0 (rts)