Poetry removes importlib_metadata and other requirements when run as `--no-dev`

• I am on the latest 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: https://hub.docker.com/_/python:3.6-alpine
• Poetry version: 1.0.3
• Link of a Gist with the contents of your pyproject.toml file: https://gist.github.com/vad/874bcd90092a98b21ae73a2982246b3c

Issue

I’m using poetry inside a docker with poetry config virtualenvs.create false. Poetry requirements are listed in my poetry.lock as dev (they probably are dependencies of some other package). When I run poetry install --no-dev the first time, the command runs fine but poetry removes its own requirements!

...
  - Removing attrs (19.3.0)
  - Removing cffi (1.14.0)
  - Removing cryptography (2.8)
  - Removing idna (2.8)
  - Removing importlib-metadata (1.5.0)
  - Removing jsonschema (3.2.0)
  - Removing pycparser (2.19)
  - Removing pyparsing (2.4.6)
  - Removing pyrsistent (0.15.7)
  - Removing zipp (3.0.0)

The second time poetry is run, I get:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/poetry/utils/_compat.py", line 15, in <module>
    from importlib import metadata
ImportError: cannot import name 'metadata'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/bin/poetry", line 5, in <module>
    from poetry.console import main
  File "/usr/local/lib/python3.6/site-packages/poetry/console/__init__.py", line 1, in <module>
    from .application import Application
  File "/usr/local/lib/python3.6/site-packages/poetry/console/application.py", line 5, in <module>
    from .commands.about import AboutCommand
  File "/usr/local/lib/python3.6/site-packages/poetry/console/commands/__init__.py", line 2, in <module>
    from .add import AddCommand
  File "/usr/local/lib/python3.6/site-packages/poetry/console/commands/add.py", line 5, in <module>
    from .init import InitCommand
  File "/usr/local/lib/python3.6/site-packages/poetry/console/commands/init.py", line 16, in <module>
    from poetry.utils._compat import OrderedDict
  File "/usr/local/lib/python3.6/site-packages/poetry/utils/_compat.py", line 18, in <module>
    import importlib_metadata as metadata
ModuleNotFoundError: No module named 'importlib_metadata'

[matthijskooijman]

One extra observation: It seems that poetry only removes packages that are mentioned in its pyproject.toml and/or poetry.lock (maybe just one, haven’t checked).

I tried installing an extra package (mysqlclient) using pip directly, then ran poetry install --no-dev and it would again remove importlib-metadata and some others (all of which are listed as (indirect) dev-dependencies), but it would not remove mysqlclient, presumably since it was not listed at all.

A workaround that seems to work, is to add poetry itself as an optional dependency:

poetry add --optional poetry

This adds a ton of extra packages to poetry.lock (all dependencies of poetry), but does not install them on poetry install. Also, it prevents removing them on poetry install --no-dev.

[finswimmer]

Hello,

the problem here is, that poetry and the package are installed in the same environment. One should never mix the installation method within one environment. Either use poetry or pip. But not both at the same time. Because they don’t know each other and break things when a package gets installed or removed by one or another.

When using virtualenvs.create false make sure poetry is installed with the installer script or as an alternative by pipx.

fin swimmer