can't install testtools because of circular dependency on fixtures.

[radix]

I realize it seems like this was an intentional decision to not support circular dependencies, but testtools apparently has a circular dependency on fixtures. It seems they refuse to break this dependency, but it is apparently not a runtime dependency -- one of them is build-time. testing-cabal/testtools#236

I'm not sure if there's a way to resolve this -- does testtools or fixtures need more metadata specified with their dependencies? can poetry just allow circular dependencies?

[sdispater]

poetry was designed so that circular dependencies would lead to an error. Circular dependencies are bad by definition, even though in this case the resolver could find a solution.

And both are runtime dependencies:

• For testtools: Requires-Dist: fixtures (>=1.3.0)
• For fixture: Requires-Dist: testtools (>=0.9.22)

That was never a problem for them before because pip doesn't come with a dependency resolver and thus would install everything without picking up the circular dependency.

So, for now, handling this case would require to change the implementation of the resolver and this is not something I want to tackle as of yet since there is more pressing matters.

However, I might come back to it at some point.

[radix]

I see, indeed I misread the ticket and now see that it's a runtime dependency and not a build-time dependency. 😢

[sdispater]

@radix Just so you know I am currently rewriting the resolver from scratch and circular dependencies, as long as they are compatible, will be supported.

[sdispater]

@radix A new prerelease (0.10.0a0) has been published. It contains the new dependency resolver which fixes this issue. So you can give it a try if you want :-)

[sdispater]

Release 0.10.0 is out and should fix this issue.

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