Fails to choose compatible version for version-less dependency

[colllin]

• I am on the latest Poetry version.

• I have searched the issues of this repo and believe that this is not a duplicate.

• N/A If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: ubuntu 16.04

• Poetry version: 0.12.17

• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/colllin/a612f1ddbafbde91b1da2a9a213bf430

Issue

👋 pipenv user trying poetry for the first time. Please forgive me if I'm misunderstanding the usage of this tool. I expected to be able to (after poetry init):

poetry add torch==1.2.*
poetry add torchvision

... and that poetry would automatically resolve the correct version of torchvision which is compatible with torch==1.2.*. Instead, I get the following:

$ poetry add torchvision
Using version ^0.4.2 for torchvision

Updating dependencies
Resolving dependencies... (0.0s)
                                                                                                           
[SolverProblemError]                                                                        
Because no versions of torchvision match >0.4.2,<0.5.0                                                   
 and torchvision (0.4.2) depends on torch (1.3.1), torchvision (>=0.4.2,<0.5.0) requires torch (1.3.1).  
So, because lulc-dvc depends on both torch (=1.2) and torchvision (^0.4.2), version solving failed.

Why is it selecting an incompatible version (^0.4.2) without accounting for existing dependencies?

[smsegal]

Are there any updates or workarounds for this? I'm getting the exact same issue with torchvision v0.5.0

[mkniewallner]

Duplicate of #707.

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