Specifying conflicts a workspace dependency with conflicting extras?

[shawnohare]

# Description of Problem

Using uv==0.5.16 I created a workspace dependency runtimes with conflicting extras cow5 and cow6 and specify the conflict in that package's pyproject.toml. I want to include runtimes[cow6] in the main dependencies group of an app package. However, it's unclear to me how to specify the conflict in app/pyproject.toml, as uv sync complains about an unconditional reference to the conflicting extra. I suspect this is potentially related to #10238?

Below is a simple bash script that should create the packages and add the attempted conflict resolution.

rm -rf ./runtimes
rm -rf ./app

printf '[tool.uv.workspace]\nmembers = ["*"]' > pyproject.toml
uv init --lib runtimes
uv add --package "runtimes" --optional "cow5" "cowsay<6" --frozen
uv add --package "runtimes" --optional "cow6" "cowsay>=6" --frozen

cat << EOF >> runtimes/pyproject.toml

[tool.uv]
conflicts = [
  [
     { extra = "cow5"},
     { extra = "cow6"},
  ],
]
EOF
# at this stage this works: uv sync --package "runtimes" --extra "cow6"


uv init app
uv add --package "app" "runtimes[cow6]" --frozen

cat << EOF >> app/pyproject.toml

[tool.uv]
conflicts = [
  [
     { package = "runtimes", extra = "cow5"},
     { package = "runtimes", extra = "cow6"},
  ],
]
EOF

echo "# runtimes/pyproject.toml"
cat runtimes/pyproject.toml
echo "# app/pyproject.toml"
cat app/pyproject.toml

# errors
uv sync

The "library" pyproject.toml is below.

# runtimes/pyproject.toml
[project]
name = "runtimes"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
authors = [
    { name = "Shawn O'Hare", email = "[email protected]" }
]
requires-python = ">=3.12"
dependencies = []

[project.optional-dependencies]
cow5 = [
    "cowsay<6",
]
cow6 = [
    "cowsay>=6",
]

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

[tool.uv]
conflicts = [
  [
     { extra = "cow5"},
     { extra = "cow6"},
  ],
]

The "app" pyproject.toml is below.

# app/pyproject.toml
[project]
name = "app"
version = "0.1.0"
description = "Add your description here"
readme = "README.md"
requires-python = ">=3.12"
dependencies = [
    "runtimes[cow6]",
]

[tool.uv.sources]
runtimes = { workspace = true }

[tool.uv]
conflicts = [
  [
     { package = "runtimes", extra = "cow5"},
     { package = "runtimes", extra = "cow6"},
  ],
]

Context and workaround

What I'm actually trying to do is utilize uv workspaces in a monorepo context where many common dependencies are pushed to dummy packages. Think pinned dependencies for machine learning runtimes, where individual projects (an app / inference endpoint) target a specific runtime. Originally I had thought to make a singular runtimes dummy package like the above, where runtime specific dependency sets are specified as optional dependencies. An obvious workaround for this particular situation is to simply make the various runtime targets separate dummy packages, but from a book-keeping perspective this seems sub-optimal (albeit very minor).