Poetry: Strange downgrades when adding new deps.

[dekoza]

• [x] I am on the latest Poetry version.
• [x] I have searched the issues of this repo and believe that this is not a duplicate.
• [x] If an exception occurs when executing a command, I executed it again in debug mode (-vvv option).

• OS version and name: Manjaro Linux, latest
• Poetry version: 1.0.9
• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/dekoza/cb68a98e677c984c1188fc2a634ada41

Issue

I observed strange downgrade when adding new deps to my project. Aside the fact that whole process takes almost 15 minutes (8 minutes resolving, 7 minutes lock writing; I blame it on aws-cdk galaxy), some packages get downgraded. Then, after the install, I run poetry update (another 15 minutes) - each downgraded package is upgraded back to latest version.

Both my pyproject.toml and example process is attached in gist link above.

[tomzx]

It appears that for the dependencies you've specified, it takes about 10s to do version solving, but that it takes a large amount of time to go through graph building (Solver._build_graph()) using poetry 1.1.10.

Through a process of adding dependencies, I've identified that aws-cdk.aws-rds and ws-cdk.aws-ecs (together), aws-cdk.aws-ecs-patterns (by itself) seems to be causing some issue. There's over 700k calls (I had to kill it) to Solver._build_graph() which doesn't appear to be normal.

Graph building will need to have better logging facilities to debug this issue :slightly_smiling_face: