`poetry install --no-root` with only poetry.lock

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

Feature Request

When doing poetry install, both pyproject.toml and poetry.lock are required. This makes sense as the package itself is installed along with its dependencies.

However, this breaks caching in Docker. Let’s say I have these lines in docker:

COPY pyproject.toml poetry.lock README.md /
RUN  poetry install --no-dev

(Note how I also need the README.md as that is referenced in the pyproject.toml)

The main problem here is: On every build, I bump the version using poetry version .... This changes the pyproject.toml file, therefore breaks the docker caching mechanism. In comparison, with an additional requirements.txt, I can do something like:

COPY requirements.txt /
RUN pip install -r requirements.txt
COPY pyproject.toml poetry.lock README.md /
RUN  poetry install --no-dev

In this case, all the dependencies (which quite often do not change between builds) can be cached. This speeds up my docker build by 80-90%, but it’s obviously ugly to have to rely on requirements.txt

FYI: I have a workaround for requirements.txt, where I simply generate it from poetry.lock:

def _poetry_lock_to_requirements_txt(start_dir):
    with open(f'{start_dir}/poetry.lock') as f:
        lock = toml.load(f)

    requirements = {package['name']: package['version']
                    for package in lock['package']}

    with open(f'{start_dir}/requirements.txt', 'w') as f:
        f.writelines(f'{name}=={version}\n' for name, version in sorted(requirements.items()))

Alternatively, I could do some trickery around when to (re-)set the version, but this is getting uglier and uglier [plus I need requirements.txt anyway due to an other issue with poetry that I find really hard to pin down - more on that soon]

I would suggest adding the flag poetry install --dependencies-only which only requires poetry.lock, not pyproject.toml

[a-recknagel]

Honest question, why would you use poetry to set up a container? pip (with export from preview builds, as dmontagu pointed out) is enough. See here for a stack overflow post where someone had a different problem with using poetry in docker, where just using pip seems a good alternative.

[mcouthon]

This issue is related to #1899. I posted my current solution for caching there, and I’ll post it here too, if it might help anyone:

# Only copying these files here in order to take advantage of Docker cache. We only want the
# next stage (poetry install) to run if these files change, but not the rest of the app.
COPY pyproject.toml poetry.lock ./

# Currently poetry install is significantly slower than pip install, so we're creating a
# requirements.txt output and running pip install with it.
# Follow this issue: https://github.com/python-poetry/poetry/issues/338
# Setting --without-hashes because of this issue: https://github.com/pypa/pip/issues/4995
RUN poetry config virtualenvs.create false \
                && poetry export --without-hashes -f requirements.txt --dev \
                |  poetry run pip install -r /dev/stdin \
                && poetry debug

COPY  . ./

# Because initially we only copy the lock and pyproject file, we can only install the dependencies
# in the RUN above, as the `packages` portion of the pyproject.toml file is not
# available at this point. Now, after the whole package has been copied in, we run `poetry install`
# again to only install packages, scripts, etc. (and thus it should be very quick).
# See this issue for more context: https://github.com/python-poetry/poetry/issues/1899
RUN poetry install --no-interaction

# We're setting the entrypoint to `poetry run` because poetry installed entry points aren't
# available in the PATH by default, but it is available for `poetry run`
ENTRYPOINT ["poetry", "run"]