Up-to-date packages are re-installed if virtualenvs.create is false

Re-opening #4254, which was closed wrongly, #4329 does not fix this bug.

• I am on the latest current master (22c3aaddc20ad74d3633738093f685fd6dbb998a) Poetry version.

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

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

• OS version and name: Ubuntu 20.04

• Poetry version: current master (22c3aaddc20ad74d3633738093f685fd6dbb998a) (also tested with version 1.2.0a2)

• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/jstriebel/6e804c769e2075be390496e68474a36c

Issue

Packages that were already installed (by poetry itself) are re-installed if virtualenvs.create is false. This bug only appears on v1.2, it does not occur on the 1.1 branch or the latest v1.1 releases. I added a reproducible case via a Dockerfile in the linked gist.

When running docker build . on those files, this produces:

Step 12/14 : RUN poetry install
 ---> Running in 73dfd5dcf683
Skipping virtualenv creation, as specified in config file.
Installing dependencies from lock file

Package operations: 3 installs, 0 updates, 2 removals

  • Removing importlib-metadata (4.6.1)
  • Removing zipp (3.5.0)
  • Installing attrs (21.2.0)
  • Installing pyrsistent (0.18.0)
  • Installing jsonschema (3.2.0)
Removing intermediate container 73dfd5dcf683
 ---> 04e982ae2043
Step 13/14 : RUN echo SECOND INSTALL!!!
 ---> Running in 7ec46c74fa47
SECOND INSTALL!!!
Removing intermediate container 7ec46c74fa47
 ---> eff9efcdee5e
Step 14/14 : RUN poetry install
 ---> Running in a877dc9c4864
Skipping virtualenv creation, as specified in config file.
Installing dependencies from lock file

Package operations: 3 installs, 0 updates, 0 removals

  • Installing attrs (21.2.0)
  • Installing pyrsistent (0.18.0)
  • Installing jsonschema (3.2.0)
Removing intermediate container a877dc9c4864

The packages are not installed twice if virtualenvs.create is true (tested by commenting out the COPY poetry.toml / line).

Possibly related previous issues: #1711, #1882 (solved in previous releases, but re-introduced in v1.2)

Given that this was broken multiple times in different ways now, and was not fixed by #4329 as intended, would it be possible to add some tests for this case as well? I'd be happy to help here, but have no experience with the poetry code-base.

Start by reproducing the Dockerfile case from the linked gist with virtualenvs.create set to false, comparing the first and second poetry install runs. Read the linked issues #4254 and #4329, then add coverage for the repeated-install behavior and verify that already installed packages are not reported as installs.