[Python] uv sync does not install dependencies into venv in GitHub Actions workflow

In a GitHub Actions workflow I use uv sync to install the dependencies of a Python project:

steps:
- name: checkout source code
uses: actions/checkout@v4
- name: Set up Python ${{ matrix.python-version }}
uses: actions/setup-python@v5
with:
python-version: ${{ matrix.python-version }}
- name: Install uv
uses: yezz123/setup-uv@v4
with:
uv-venv: ".venv"
- name: Install dependencies
run: uv sync

- name: Ruff check
run: uv run ruff check src tests


However, this gives me the following error:



If I run uv sync on my laptop, it works fine and it installs ruff and other development dependencies. Why does it not work in GitHub Actions?

Here is my pyproject.toml file:

[project]
name = "pyml-regression-example1"
version = "0.1.0"
description = "Python Machine Learning Regression Example: Life Expectancy"
readme = "README.md"
requires-python = ">=3.11"
dependencies = [
"click>=8.1.7",
"colorama>=0.4.6",
"matplotlib>=3.9.2",
"numpy>=2.1.1",
"platformdirs>=4.3.6",
"scikit-learn>=1.5.2",
"sphinx-autodoc-typehints>=2.0.0",
"sphinx-click-rst-to-ansi-formatter>=0.1.1",
]
packages = [{include = "life_expectancy", from = "src"}]

[project.scripts]
life-expectancy = "life_expectancy.main:main"

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

[tool.hatch.build.targets.wheel]
packages = ["src/life_expectancy"]

[tool.uv]
dev-dependencies = [
"coverage>=7.6.1",
"mypy>=1.11.2",
"pytest-mock>=3.14.0",
"pytest>=8.3.3",
"ruff>=0.6.6",
"sphinx-rtd-theme>=2.0.0",
"sphinx>=7.0.0",
"sphinx-click>=6.0.0",
"types-click>=7.1.8",
"types-colorama>=0.4.15.20240311",
"pre-commit>=3.8.0",
"rstcheck>=6.2.4",
"tox>=4.20.0",
"types-requests>=2.32.0.20240914",
]

[tool.coverage.report]
fail_under = 100

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