nox: use uv as default venv backend

Author: dtrifiro

.github/workflows/tests.yaml

@@ -14,8 +14,10 @@ env:
   # facilitate testing by building vLLM for CPU when needed
   VLLM_CPU_DISABLE_AVX512: "true"
   VLLM_TARGET_DEVICE: "cpu"
-  # prefer torch cpu version
-  PIP_EXTRA_INDEX_URL: "https://download.pytorch.org/whl/cpu"
+  # prefer index for torch cpu version
+  UV_EXTRA_INDEX_URL: "https://download.pytorch.org/whl/cpu"
+  # have uv match pip's behaviour for extra index operations
+  UV_INDEX_STRATEGY: "unsafe-best-match"
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
@@ -56,19 +58,18 @@ jobs:
             ccache \
             libnuma-dev libdnnl-dev opencl-dev
 
-      - name: Set up Python ${{ matrix.pyv }}
-        uses: actions/setup-python@v5
-        id: setup-python
+      - name: Install the latest version of uv
+        uses: astral-sh/setup-uv@v5
         with:
+          version: "latest"
           python-version: ${{ matrix.pyv }}
-          cache: pip
-          cache-dependency-path: pyproject.toml
+          enable-cache: true
+          cache-dependency-glob: |
+            pyproject.toml
 
-      - name: Upgrade pip and nox
+      - name: Install nox
         run: |
-          python -m pip install --upgrade pip nox
-          pip --version
-          nox --version
+          uv pip install nox
 
       - name: nox envs cache
         id: cache

noxfile.py

@@ -5,22 +5,29 @@
 
 nox.options.reuse_existing_virtualenvs = True
 nox.options.sessions = "lint", "tests"
+nox.options.default_venv_backend = "uv"
 locations = "src", "tests"
 
-versions = ["3.9", "3.10", "3.11", "3.12"]
+versions = [
+    "3.12",
+    "3.11",
+    "3.10",
+    "3.9",
+]
 
 
 @nox.session(python=versions)
 def tests(session: nox.Session) -> None:
     if vllm_version := os.getenv("VLLM_VERSION_OVERRIDE"):
-        session.install(vllm_version, "-v")
+        session.install(vllm_version)
 
     session.install(".[tests]")
 
     session.run(
         "pytest",
         "--cov",
         "--cov-config=pyproject.toml",
+        "--no-cov-on-fail",
         *session.posargs,
         env={"COVERAGE_FILE": f".coverage.{session.python}"},
     )
@@ -58,8 +65,11 @@ def dev(session: nox.Session) -> None:
     venv_dir = Path(args[0])
 
     session.log(f"Setting up virtual environment in {venv_dir}")
-    session.install("virtualenv")
-    session.run("virtualenv", venv_dir, silent=True)
+    session.install("uv")
+    session.run("uv", "venv", venv_dir, silent=True)
 
     python = venv_dir / "bin/python"
-    session.run(python, "-m", "pip", "install", "-e", ".[dev]", external=True)
+    session.run(
+        *f"{python} -m uv pip install -e .[dev]".split(),
+        external=True,
+    )