Error out when using the same normalised source twice

[mkniewallner]

When mapping dependencies to define sources, because of the TOML specification, uv will raise an error if defining the same source twice. For instance with this pyproject.toml:

[project]
name = "foo"
version = "0.1.0"
dependencies = ["python-multipart"]

[tool.uv.sources]
python-multipart = { url = "https://files.pythonhosted.org/packages/3d/47/444768600d9e0ebc82f8e347775d24aef8f6348cf00e9fa0e81910814e6d/python_multipart-0.0.9-py3-none-any.whl" }
python-multipart = { url = "https://files.pythonhosted.org/packages/c0/3e/9fbfd74e7f5b54f653f7ca99d44ceb56e718846920162165061c4c22b71a/python_multipart-0.0.8-py3-none-any.whl" }

the following error will be raised:

$ uv lock
warning: Failed to parse `pyproject.toml` during settings discovery:
  TOML parse error at line 8, column 1
    |
  8 | python-multipart = { url = "https://files.pythonhosted.org/packages/c0/3e/9fbfd74e7f5b54f653f7ca99d44ceb56e718846920162165061c4c22b71a/python_multipart-0.0.8-py3-none-any.whl" }
    | ^
  duplicate key `python-multipart` in table `tool.uv.sources`

error: Failed to parse: `pyproject.toml`
  Caused by: TOML parse error at line 8, column 1
  |
8 | python-multipart = { url = "https://files.pythonhosted.org/packages/c0/3e/9fbfd74e7f5b54f653f7ca99d44ceb56e718846920162165061c4c22b71a/python_multipart-0.0.8-py3-none-any.whl" }
  | ^
duplicate key `python-multipart` in table `tool.uv.sources`

(btw not sure we should have both a warning and error here)

But while uv applies normalisation for sources (similarly to dependencies), it will not error out if defining the same source twice with different casing that would result in the same name after normalisation:

[project]
name = "foo"
version = "0.1.0"
dependencies = ["python-multipart"]

[tool.uv.sources]
python-multipart = { url = "https://files.pythonhosted.org/packages/3d/47/444768600d9e0ebc82f8e347775d24aef8f6348cf00e9fa0e81910814e6d/python_multipart-0.0.9-py3-none-any.whl" }
python_multipart = { url = "https://files.pythonhosted.org/packages/c0/3e/9fbfd74e7f5b54f653f7ca99d44ceb56e718846920162165061c4c22b71a/python_multipart-0.0.8-py3-none-any.whl" }

Here, locking will work, and will end up choosing the latest source defined in the list (here in python_multipart, and if reversing the list, python-multipart is chosen instead).

Should uv also error out in this case, like it does when using the exact same casing?

[charliermarsh]

Yeah, I think we should probably error in both cases. Good find.

[charliermarsh]

(btw not sure we should have both a warning and error here)

Agree though it's somewhat annoying to fix because these happen very far apart from one another.

[mkniewallner]

(btw not sure we should have both a warning and error here)

Agree though it's somewhat annoying to fix because these happen very far apart from one another.

Yeah to be fair this is really just a tiny annoyance, mentioned it just because I stumbled across it 😄

[charliermarsh]

It bothers me lol.