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Merged
sbee-mq merged 1 commit into from
Sep 26, 2026
Merged

nix: make python shells reliable across hosts #5

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19 changes: 15 additions & 4 deletions nix/devshell.nix
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,8 @@ let
env = {
UV_PYTHON = pythonSet.python.interpreter;
UV_PYTHON_DOWNLOADS = "never";
UV_CONCURRENT_DOWNLOADS = "4";
UV_HTTP_TIMEOUT = "600";
};
shellHook = ''
unset PYTHONPATH
Expand All @@ -38,23 +40,32 @@ let
}
);

driverLibs = lib.optionalString pkgs.stdenv.hostPlatform.isLinux "${pkgs.addDriverRunpath.driverLink}/lib";

uv2nix = mkDevShell {
packages = [ virtualenv ];
env.UV_NO_SYNC = "1";
env = {
UV_NO_SYNC = "1";
}
// lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
LD_LIBRARY_PATH = driverLibs;
};
};

impure = mkDevShell {
packages = [ pythonSet.python ];
env = lib.optionalAttrs pkgs.stdenv.hostPlatform.isLinux {
LD_LIBRARY_PATH = lib.makeLibraryPath [ pkgs.stdenv.cc.cc.lib ];
LD_LIBRARY_PATH = lib.makeLibraryPath [ pkgs.stdenv.cc.cc.lib ] + ":" + driverLibs;
};
shellHook = ''
uv sync
if [ ! -x .venv/bin/python ] || [ uv.lock -nt .venv/pyvenv.cfg ]; then
uv sync --frozen
fi
. .venv/bin/activate
'';
};
in
{
inherit impure uv2nix;
default = impure;
default = uv2nix;
}
59 changes: 39 additions & 20 deletions nix/python.nix
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Expand Up @@ -9,34 +9,53 @@ let

pythonOverlay = workspace.mkPyprojectOverlay { sourcePreference = "wheel"; };

# sdist-only deps that build with setuptools but omit it from
# build-system.requires, so uv2nix has nothing to bootstrap them with.
needsSetuptools = [
"watchdog"
];
packageOverrides = final: prev: {
# uv.lock omits build-system metadata required for this sdist build.
watchdog = prev.watchdog.overrideAttrs (old: {
nativeBuildInputs =
old.nativeBuildInputs
++ final.resolveBuildSystem {
setuptools = [ ];
};
});
};

pythonOverrides =
final: prev:
lib.genAttrs needsSetuptools (
name:
prev.${name}.overrideAttrs (old: {
nativeBuildInputs = (old.nativeBuildInputs or [ ]) ++ [ final.setuptools ];
})
);
isCudaWheel =
name:
lib.hasPrefix "nvidia-" name
|| builtins.elem name [
"torch"
"triton"
];

cudaWheelOverrides =
_final: prev:
lib.mapAttrs (
_name: package:
package.overrideAttrs {
# Linux torch depends on CUDA libraries shipped by sibling wheels.
# autoPatchelf cannot resolve them across separate derivations.
autoPatchelfIgnoreMissingDeps = true;
}
) (lib.filterAttrs (name: _package: isCudaWheel name) prev);
in
{
inherit workspace;

mkPythonSet =
pkgs:
let
overlays = [
inputs.pyproject-build-systems.overlays.wheel
pythonOverlay
packageOverrides
]
++ lib.optionals pkgs.stdenv.hostPlatform.isLinux [
cudaWheelOverrides
];
in
(pkgs.callPackage inputs.pyproject-nix.build.packages {
python = pkgs.python314;
}).overrideScope
(
lib.composeManyExtensions [
inputs.pyproject-build-systems.overlays.wheel
pythonOverlay
pythonOverrides
]
);
(lib.composeManyExtensions overlays);
}
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