multiple versions of the same package can be installed in some cases when using conflicting extras

[BurntSushi]

I found the problem by trying to reproduce the problem on a new repo. The problem is with package torchmetrics. When it is in the workspace package/dependency this case exists. I have yet not inspect what can be wrong with that package configuration.

Minimal example:

Child:

[project]
name = "child-surface"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
requires-python = ">=3.12"
dependencies = [
    "torchmetrics>=1.1.0",
]


[project.optional-dependencies]
cpu = [
    "torch==2.4.1", 
    "torchvision==0.19.1"
]
gpu = [
    "torch==2.4.1", 
    "torchvision==0.19.1",
    "nvidia-dali-cuda120==1.30.0",
]
[tool.uv]
conflicts = [
  [
    { extra = "cpu" },
    { extra = "gpu" },
  ],
]

[tool.uv.sources]
torch = [
  { index = "pytorch-cpu", extra = "cpu" },
  { index = "pytorch-cu124", extra = "gpu" },
]
torchvision = [
  { index = "pytorch-cpu", extra = "cpu" },
  { index = "pytorch-cu124", extra = "gpu" },
]
[[tool.uv.index]]
name = "pytorch-cpu"
url = "https://download.pytorch.org/whl/cpu"
explicit = true

[[tool.uv.index]]
name = "pytorch-cu124"
url = "https://download.pytorch.org/whl/cu124"
explicit = true

Parent:

[project]
name = "parent-surface"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
requires-python = ">=3.12"
dependencies = []

[tool.uv.sources]
child-surface = [{ workspace = true  },]

[tool.uv.workspace]
members = ["child-surface"]


[project.optional-dependencies]
cpu = [
    "child-surface[cpu]>=0.0.1", 
]
gpu = [
    "child-surface[gpu]>=0.0.1", 
]

[tool.uv]
conflicts = [
  [
    { extra = "cpu" },
    { extra = "gpu" },
  ],
]

Full zipped example with lock file:
parent-surface.zip

---

Edit: Looking at their repo and build system in setup.py I see that they define base requirements which is just torch >=2.0.0, <2.7.0

So uv resolver has installed torch==2.4.1+cu124 and then installs torch==2.4.1 which is strange having two different versions of the same package

This behavior changed after introducing this change

Originally posted by @mchalecki in #10590

[BurntSushi]

After creating the above two pyproject.toml files (pyproject.toml and child-surface/pyproject.toml), just run uv sync --extra cpu and I at least get (on Linux):

 + torch==2.4.1
 + torch==2.4.1+cpu

The same thing happens for uv sync --extra gpu, but you get torch==2.4.1+cu124 instead.

My guess here is that when I relaxed the error checking around unconditional enabling of conflicting extras in #10875, this may have uncovered a new bug in how forks are created and managed for conflicting extras? Not sure. But the relevant lines in the lock file are:

[[package]]
name = "torchmetrics"
version = "1.6.1"
source = { registry = "https://pypi.org/simple" }
dependencies = [
    { name = "lightning-utilities" },
    { name = "numpy" },
    { name = "packaging" },
    { name = "torch", version = "2.4.1", source = { registry = "https://download.pytorch.org/whl/cpu" }, marker = "(platform_machine == 'aarch64' and sys_platform == 'linux' and extra == 'extra-13-child-surface-cpu') or (platform_machine != 'aarch64' and extra == 'extra-13-child-surface-cpu' and extra == 'extra-13-child-surface-gpu') or (platform_machine != 'aarch64' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu') or (sys_platform == 'darwin' and extra == 'extra-13-child-surface-cpu') or (sys_platform != 'linux' and extra == 'extra-13-child-surface-cpu' and extra == 'extra-13-child-surface-gpu') or (sys_platform != 'linux' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu') or (sys_platform == 'darwin' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu') or (extra != 'extra-13-child-surface-cpu' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu')" },
    { name = "torch", version = "2.4.1", source = { registry = "https://download.pytorch.org/whl/cu124" }, marker = "(platform_machine == 'aarch64' and sys_platform == 'linux' and extra == 'extra-13-child-surface-gpu') or (platform_machine != 'aarch64' and extra == 'extra-13-child-surface-cpu' and extra == 'extra-13-child-surface-gpu') or (platform_machine != 'aarch64' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu') or (sys_platform != 'linux' and extra == 'extra-13-child-surface-cpu' and extra == 'extra-13-child-surface-gpu') or (sys_platform != 'linux' and extra != 'extra-13-child-surface-cpu' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu') or (extra != 'extra-13-child-surface-gpu' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu')" },
    { name = "torch", version = "2.4.1", source = { registry = "https://pypi.org/simple" }, marker = "(extra == 'extra-13-child-surface-cpu' and extra == 'extra-13-child-surface-gpu') or (extra != 'extra-13-child-surface-cpu' and extra != 'extra-13-child-surface-gpu')" },
    { name = "torch", version = "2.4.1+cpu", source = { registry = "https://download.pytorch.org/whl/cpu" }, marker = "(platform_machine != 'aarch64' and sys_platform == 'linux' and extra == 'extra-13-child-surface-cpu') or (sys_platform != 'darwin' and sys_platform != 'linux' and extra == 'extra-13-child-surface-cpu') or (sys_platform == 'darwin' and extra == 'extra-13-child-surface-cpu' and extra == 'extra-13-child-surface-gpu') or (sys_platform == 'linux' and extra == 'extra-13-child-surface-cpu' and extra == 'extra-13-child-surface-gpu') or (sys_platform == 'darwin' and extra != 'extra-13-child-surface-gpu' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu') or (sys_platform == 'linux' and extra == 'extra-13-child-surface-cpu' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu') or (extra != 'extra-13-child-surface-cpu' and extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu')" },
    { name = "torch", version = "2.4.1+cu124", source = { registry = "https://download.pytorch.org/whl/cu124" }, marker = "(platform_machine != 'aarch64' and extra == 'extra-13-child-surface-gpu') or (sys_platform != 'linux' and extra == 'extra-13-child-surface-gpu') or (extra == 'extra-13-child-surface-cpu' and extra == 'extra-13-child-surface-gpu') or (extra == 'extra-14-parent-surface-cpu' and extra == 'extra-14-parent-surface-gpu')" },
]
sdist = { url = "https://files.pythonhosted.org/packages/14/c5/8d916585d4d6eb158105c21b28cd4b0ed296d74e499bf8f104368de16619/torchmetrics-1.6.1.tar.gz", hash = "sha256:a5dc236694b392180949fdd0a0fcf2b57135c8b600e557c725e077eb41e53e64", size = 540022 }
wheels = [
    { url = "https://files.pythonhosted.org/packages/9d/e1/84066ff60a20dfa63f4d9d8ddc280d5ed323b7f06504dbb51c523b690116/torchmetrics-1.6.1-py3-none-any.whl", hash = "sha256:c3090aa2341129e994c0a659abb6d4140ae75169a6ebf45bffc16c5cb553b38e", size = 927305 },
]

The conflict markers are way too complicated me to digest at a glance here, so I think this one requires a bit more investigation.

[BurntSushi]

And note that the conflicting extras defined in the parent package here are superfluous. If I remove them, the bug remains.