[Python] How can I solve this issue running a uv command when building a docker image

I am using uv in a python project to manage dependencies. I worte the following dockerfile based on some examples provided by the uv github repo.

# Use a Python image with uv pre-installed
FROM ghcr.io/astral-sh/uvython3.12-bookworm-slim

# Install the project into `/app`
WORKDIR /app

COPY pyproject.toml uv.lock ./

# Enable bytecode compilation
ENV UV_COMPILE_BYTECODE=1

# Copy from the cache instead of linking since it's a mounted volume
ENV UV_LINK_MODE=copy

# Print Python and uv version for debugging
RUN python --version && which python && uv --version

# Install dependencies
RUN --mount=type=cache,target=/root/.cache/uv \
--mount=type=bind,source=uv.lock,target=uv.lock \
--mount=type=bind,source=pyproject.toml,target=pyproject.toml \
uv sync --locked --no-install-project --no-dev


# # Then, add the rest of the project source code and install it
# # Installing separately from its dependencies allows optimal layer caching
COPY . /app
# RUN --mount=type=cache,target=/root/.cache/uv \
# uv sync --locked --no-dev

# Place executables in the environment at the front of the path
ENV PATH="/app/.venv/bin:$PATH"

# Reset the entrypoint, don't invoke `uv`
ENTRYPOINT []

# Run the python script using `uv run`
CMD ["uv", "run", "services/trades/src/trades/main.py"]


When I try to build the image using the docker build --no-cache -t trades:dev -f docker/trades.Dockerfile . command I get this error:

5.509 error: The lockfile at `uv.lock` needs to be updated, but `--locked` was provided. To update the lockfile, run `uv lock`.
------
trades.Dockerfile:19
--------------------
18 | # Install dependencies
19 | >>> RUN --mount=type=cache,target=/root/.cache/uv \
20 | >>> --mount=type=bind,source=uv.lock,target=uv.lock \
21 | >>> --mount=type=bind,source=pyproject.toml,target=pyproject.toml \
22 | >>> uv sync --locked --no-install-project --no-dev
23 |
--------------------
ERROR: failed to solve: process "/bin/sh -c uv sync --locked --no-install-project --no-dev" did not complete successfully: exit code: 2
make: *** [Makefile:5: build] Error 1


Of course I tried with running uv lock but the issue was not resolved. I also checked the python version of the base image and compared with the python version of the local project, and they are the same.

I deleted the --locked tag and the docker image was built without issues, so I extracted the uv.lock file from the relying container and compared it with the uv.lock file under the local project folder. Both files are absolutely the same.

I still want to build the image using the --locked tag to guarantee a stable environment between the docker container and the local folder.

Any suggestions please?

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