Could not find a version that matches with latest version of Mypy and Pylint

Follow up of #2785 (and probably other).

Got the same good-old “resolver issue” again today:

• pylint 2.3.0 was released today on Pypi.
• pylint 2.3.0 wants astroid>=2.2.0
• astroid 2.2.0 want typed-ast>=1.4.0

In my pipfile I also have pylint = "*" and mypy = "*".

And latest version of mypy want typed-ast<1.4.0. So the resolver on pipenv update --clear fails witht the infamous error:

Could not find a version that matches typed-ast<1.3.0,<1.4.0,>=1.3.1

In short: as of today, latest versions of mypy and pylint packages have incompatible dependencies.

Fixing by add this in the Pipfile:

pylint = "<2.3.0"
typed-ast = "<1.4.0,>=1.3.1"
astroid = "<2.2.0"

To prevent update of pylint.

I understand digging into the resolver is a really complex task, and I tried it and failed at doing anything relevant, but still, I hope one good lad here find time to dig into this and find a way to have pipenv finds itself it should not take the latest version of pylint package in this case, and try with a previous version.

Expected behavior:

• pylint version is updated, the resolver fails at the end with “Could not find a version” error.
• previous versions available on pypi is tried, and so on, until the same version that were on Pipfile.lock. If not present, a depth limit may be set to avoid to try every version of pylint package
• even in case of failure, pipenv update --clear should end in success (providing the lock file is still coherent) but add an explicit warning telling 2 packages have incompatible dependency rule in their latest version available on Pypi.

[superdev810]

@gsemet did you try to force to set mypy==0.660 in Pipfile? I think after mypy pacakge updated in Feb 9, it’s happening nowadays.

[techalchemy]

we have the OK to incorporate passa, but we have a lot of legwork to do first cleaning up other issues. The issue here is just that piptools doesn’t backtrack to resolve conflicts after it makes a decision. Passa handles that issue