find activate script with sysconfig

ci.sh

@@ -40,7 +40,7 @@ echo "::group::Install dependencies"
 curl-harder https://astral.sh/uv/0.4.30/install.sh -o uv-install.sh
 UV_UNMANAGED_INSTALL="./.uv-bin" sh uv-install.sh
 ./.uv-bin/uv venv .venv
-source .venv/bin/activate
+source $(python ./src/trio/_tools/find_activate_script.py .venv)
 ./.uv-bin/uv pip install uv -c test-requirements.txt
 python -m uv pip install 'build[uv]' -c test-requirements.txt
 python -m uv --version

src/trio/_tests/tools/test_find_activate_script.py

@@ -0,0 +1,21 @@
+import os
+import pathlib
+import venv
+
+import pytest
+
+from trio._tools import find_activate_script
+
+
+def test_find_activate_script(
+    tmp_path: pathlib.Path,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    env_dir = tmp_path / "venv"
+    venv.create(env_dir)
+    find_activate_script.main([os.fsdecode(env_dir)])
+    captured = capsys.readouterr()
+    assert captured.err == ""
+    activate = pathlib.Path(captured.out.removesuffix("\n"))
+    assert activate.exists()
+    assert activate.name == "activate"

src/trio/_tools/find_activate_script.py

@@ -0,0 +1,58 @@
+"""
+Script to find the activate script in a virtual environment.
+
+Has only stdlib dependencies because it runs before any package is installed.
+"""
+
+from __future__ import annotations
+
+import argparse
+import os
+import pathlib
+import sys
+import sysconfig
+
+
+def _venv_path(env_dir: str, name: str) -> str:
+    vars_ = {
+        "base": env_dir,
+        "platbase": env_dir,
+        "installed_base": env_dir,
+        "installed_platbase": env_dir,
+    }
+    return sysconfig.get_path(name, scheme="venv", vars=vars_)
+
+
+if sys.version_info >= (3, 11):
+
+    def _get_binpath(v: pathlib.Path) -> pathlib.Path:
+        return pathlib.Path(_venv_path(env_dir=os.fsdecode(v), name="scripts"))
+
+elif sys.platform == "win32":
+
+    def _get_binpath(v: pathlib.Path) -> pathlib.Path:
+        return v / "Scripts"
+
+else:
+
+    def _get_binpath(v: pathlib.Path) -> pathlib.Path:
+        return v / "bin"
+
+
+def _get_activate_script(v: pathlib.Path) -> pathlib.Path:
+    return _get_binpath(v) / "activate"
+
+
+def main(args: list[str] | None = None) -> int:
+    parser = argparse.ArgumentParser(
+        description="Find the activate script for a given virtual environment",
+    )
+    parser.add_argument("filename", type=pathlib.Path)
+    parsed_args = parser.parse_args(args=args)
+    activate = _get_activate_script(parsed_args.filename)
+    print(activate)
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())