`pip-compile` fails to parse a `pyproject.toml` with self-references when supplied as a relative path

[merelcht]

With the latest pip-tools version 7.5.0 the pip-compile command fails when Click is one of the project dependencies.

Whereas with the previous versions it just runs fine.

Environment Versions

1. OS Type: Both Unix and Windows (see broken pip-compile builds here https://github.com/kedro-org/kedro/actions/runs/16662774430/job/47182583460)
2. Python version: $ python -V: all versions from 3.9-3.12
3. pip version: $ pip --version: pip 25.2
4. pip-tools version: $ pip-compile --version 7.5.0

Steps to replicate

1. Clone out the kedro repository: https://github.com/kedro-org/kedro
2. Install the kedro dependencies : make install-test-requirements
make install-pre-commit, uv pip install "pip-tools>=6.5"
3. Run pip-compile

Expected result

A successful pip-compile e.g.:

# This file is autogenerated by pip-compile with Python 3.11
# by the following command:
#
#    pip-compile
#
antlr4-python3-runtime==4.9.3
    # via omegaconf
appdirs==1.4.4
    # via kedro-telemetry
arrow==1.3.0
    # via cookiecutter
attrs==25.3.0
    # via
    #   kedro
    #   kedro (pyproject.toml)
binaryornot==0.4.4
    # via cookiecutter
build==1.2.2.post1
    # via
    #   kedro
    #   kedro (pyproject.toml)
cachetools==6.1.0
    # via
    #   kedro
    #   kedro (pyproject.toml)
certifi==2025.7.14
    # via requests
chardet==5.2.0
    # via binaryornot
charset-normalizer==3.4.2
    # via requests
click==8.1.8
    # via
    #   cookiecutter
    #   kedro
    #   kedro (pyproject.toml)
cookiecutter==2.6.0
    # via
    #   kedro
    #   kedro (pyproject.toml)
dynaconf==3.2.11
    # via
    #   kedro
    #   kedro (pyproject.toml)
fsspec==2025.7.0
    # via
    #   kedro
    #   kedro (pyproject.toml)
gitdb==4.0.12
    # via gitpython
gitpython==3.1.45
    # via
    #   kedro
    #   kedro (pyproject.toml)
idna==3.10
    # via requests
importlib-metadata==8.7.0
    # via
    #   kedro
    #   kedro (pyproject.toml)
importlib-resources==6.5.2
    # via
    #   kedro
    #   kedro (pyproject.toml)
jinja2==3.1.6
    # via cookiecutter
kedro==1.0.0
    # via kedro-telemetry
kedro-telemetry==0.6.3
    # via
    #   kedro
    #   kedro (pyproject.toml)
markdown-it-py==3.0.0
    # via rich
markupsafe==3.0.2
    # via jinja2
mdurl==0.1.2
    # via markdown-it-py
more-itertools==10.7.0
    # via
    #   kedro
    #   kedro (pyproject.toml)
omegaconf==2.3.0
    # via
    #   kedro
    #   kedro (pyproject.toml)
packaging==25.0
    # via build
parse==1.20.2
    # via
    #   kedro
    #   kedro (pyproject.toml)
pluggy==1.6.0
    # via
    #   kedro
    #   kedro (pyproject.toml)
pygments==2.19.2
    # via rich
pyproject-hooks==1.2.0
    # via build
python-dateutil==2.9.0.post0
    # via arrow
python-slugify==8.0.4
    # via cookiecutter
pyyaml==6.0.2
    # via
    #   cookiecutter
    #   kedro
    #   kedro (pyproject.toml)
    #   omegaconf
requests==2.32.4
    # via
    #   cookiecutter
    #   kedro-telemetry
rich==14.1.0
    # via
    #   cookiecutter
    #   kedro
    #   kedro (pyproject.toml)
six==1.17.0
    # via python-dateutil
smmap==5.0.2
    # via gitdb
text-unidecode==1.3
    # via python-slugify
toml==0.10.2
    # via
    #   kedro
    #   kedro (pyproject.toml)
types-python-dateutil==2.9.0.20250708
    # via arrow
typing-extensions==4.14.1
    # via
    #   kedro
    #   kedro (pyproject.toml)
urllib3==2.5.0
    # via requests
zipp==3.23.0
    # via importlib-metadata

Actual result

{25-08-01 10:03}M-HLJY4F7K07:~/Projects/kedro@main Merel_Theisen% pip-compile
Traceback (most recent call last):
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/bin/pip-compile", line 10, in <module>
    sys.exit(cli())
             ^^^^^
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/click/core.py", line 1161, in __call__
    return self.main(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/click/core.py", line 1082, in main
    rv = self.invoke(ctx)
         ^^^^^^^^^^^^^^^^
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/click/core.py", line 1443, in invoke
    return ctx.invoke(self.callback, **ctx.params)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/click/core.py", line 788, in invoke
    return __callback(*args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/click/decorators.py", line 33, in new_func
    return f(get_current_context(), *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/piptools/scripts/compile.py", line 371, in cli
    metadata = build_project_metadata(
               ^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/piptools/build.py", line 159, in build_project_metadata
    project_metadata = maybe_statically_parse_project_metadata(src_file)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/piptools/build.py", line 106, in maybe_statically_parse_project_metadata
    requirement.url = src_file.parent.as_uri()
                      ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/pathlib.py", line 566, in as_uri
    raise ValueError("relative path can't be expressed as a file URI")
ValueError: relative path can't be expressed as a file URI

[webknjaz]

The traceback doesn't seem to be related to Click. Not sure how you got to that conclusion...

Any chance to have a minimal reproducer per https://sscce.org ?

Also, does using older pip versions change anything?

[merelcht]

The traceback doesn't seem to be related to Click. Not sure how you got to that conclusion...

Up the stacktrace it points to parts of the click library e.g. File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/click/core.py", line 1161, in __call__

Any chance to have a minimal reproducer per https://sscce.org ?

Will create one later when I have some time 🙂 (FYI we unblocked our failing builds by using uv pip compile instead, so it's less urgent to get this fixed.)

Also, does using older pip versions change anything?

I tried a random older version of pip 24.2, but still get the same error.

[webknjaz]

The traceback doesn't seem to be related to Click. Not sure how you got to that conclusion...

Up the stacktrace it points to parts of the click library e.g. File "/Users/Merel_Theisen/anaconda3/envs/kedro/lib/python3.11/site-packages/click/core.py", line 1161, in __call__

That's only because pip-tools uses click for its own CLI. It will always be there in every traceback. I don't think it's related. The trace seems to explode when converting relative file paths, it seems. This might be related to @sirosen's recent refactoring of output.

Any chance to have a minimal reproducer per https://sscce.org ?

Will create one later when I have some time 🙂 (FYI we unblocked our failing builds by using uv pip compile instead, so it's less urgent to get this fixed.)

Thanks, this would be great. Alternatively, you could send a PR with a failing test per https://pganssle-talks.github.io/xfail-lightning/.

Also, does using older pip versions change anything?

I tried a random older version of pip 24.2, but still get the same error.

That tracks, given how the traceback looks..

[becheru]

Dear all,

The problem is related to click but not caused by it. If you try to install click==8.2.1 (latest version) and pip-tools==7.4.1, the issue does not appear. However, if you simply jump to pip-tools==7.5.0 (relased yesterday) you will get the error.

As for easy replicability here are my steps:

1. docker run -it --rm -v /home/<path_to_python_project>:/tmp/python_project --entrypoint /bin/bash python:3.11.7-bullseye, Note: under python_project you need to have pyproject.toml
2. pip install click==8.2.1 pip-tools==7.5.0 flit_core
3. cd /tmp/python_project
4. pip-compile --verbose --strip-extras --no-build-isolation --annotate --output-file requirements.txt pyproject.toml

[sirosen]

I think this problem is not related to click in any direct way. Maybe selecting a newer click impacts other parts of the dependency tree, but I wouldn't focus too much on it.

This looks like a problem related to maybe_statically_parse_project_metadata?
Did you have relative paths in your project.dependencies or build-system.requires lists? Looking at the linked project, it doesn't look problematic to me.

There are some build backends which support spec non-compliant data in these fields. Technically, you "can't" (at least, if we're talking PEP 621/517 data) put relative paths into the project or build tables.

---

I haven't had time to dig in deeply yet, but given that the static parsing of pyproject.toml is new in v7.5.0, and it's in those tracebacks near the bottom of the trace, I think it's likely that it's somehow implicated.

[alexrashed]

We are also seeing this issue, and I suspect this is being caused by extras self-referencing the package.
I verified this with this minimal reproducer pyproject.toml:

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

[project]
name = "pip-tools-self-reference"
version = "0.1.0"

[project.optional-dependencies]
test-extra = [
]
text-extra-self-reference = [
    "pip-tools-self-reference[test-extra]"
]

And here are the commands to verify that this minimal pyproject.toml triggers the reported issue with pip-tools==7.5.0:

python3 -m venv .venv
source .venv/bin/activate
pip install "pip-tools<7.5.0"
pip-compile # <- successful with versions lower than 7.5.0
pip install "pip-tools==7.5.0"
pip-compile # <- fails with the error above

[webknjaz]

@alexrashed thanks for posting the reproducer! This should help us narrow it down.