Install dependencies from pyproject.toml but not the package

Question

I have a python package that I want to install inside a docker file.

pyproject.toml looks like:

[build-system]
requires = ["setuptools>=61.0"]
build-backend = "setuptools.build_meta"

[project]
name = "bar"
dependencies = [
    "pandas",
]

[project.optional-dependencies]
foo = [
    "matplotlib",
]

... and Dockerfile:

# ...
WORKDIR /app
COPY . /app
RUN pip install /app

This installs the dependencies (in this example, pandas) on every build, which I want to avoid to save developer time, since pyproject.toml is rarely touched.

How can I install only pandas (the dependencies listed pyproject.toml) without having to COPY . and installing bar.

I want to avoid:

• adopt other tools like poetry
• create a requirements.txt and use dynamic keyword in pyproject.toml, because I have optional-dependencies and I want to keep the list of dependencies as close together (i.e. same file) as possible.

Something like:

# ...
WORKDIR /app
COPY ./pyproject.toml /app/
RUN pip install --requirements-from /app/pyproject.toml  # <-- HERE
COPY . /app
RUN pip install /app  # <-- Installs `bar` only. All dependencies already installed.