Restore uv $PATH lookup with logging message

src/build/env.py

@@ -279,13 +279,24 @@ def create(self, path: str) -> None:
         import venv
 
         self._env_path = path
+
+        try:
+            import uv
+
+            self._uv_bin = uv.find_uv_bin()
+        except (ModuleNotFoundError, FileNotFoundError):
+            self._uv_bin = shutil.which('uv')
+            if self._uv_bin is None:
+                msg = 'uv executable not found'
+                raise RuntimeError(msg) from None
+
+            _ctx.log(f'Using external uv from {self._uv_bin}')
+
         venv.EnvBuilder(symlinks=_fs_supports_symlink(), with_pip=False).create(self._env_path)
         self.python_executable, self.scripts_dir, _ = _find_executable_and_scripts(self._env_path)
 
     def install_requirements(self, requirements: Collection[str]) -> None:
-        import uv
-
-        cmd = [uv.find_uv_bin(), 'pip']
+        cmd = [self._uv_bin, 'pip']
         if _ctx.verbosity > 1:
             # uv doesn't support doubling up -v unlike pip.
             cmd += ['-v']

tests/test_env.py

@@ -2,6 +2,7 @@
 from __future__ import annotations
 
 import logging
+import shutil
 import subprocess
 import sys
 import sysconfig
@@ -262,3 +263,28 @@ def test_requirement_installation(
 ):
     with build.env.DefaultIsolatedEnv(installer=installer) as env:
         env.install([f'test-flit @ {Path(package_test_flit).as_uri()}'])
+
+
+def test_external_uv_detection_success(
+    caplog: pytest.LogCaptureFixture,
+    mocker: pytest_mock.MockerFixture,
+):
+    mocker.patch.dict(sys.modules, {'uv': None})
+
+    with build.env.DefaultIsolatedEnv(installer='uv'):
+        pass
+
+    assert any(
+        r.message == f'Using external uv from {shutil.which("uv", path=sysconfig.get_path("scripts"))}' for r in caplog.records
+    )
+
+
+def test_external_uv_detection_failure(
+    mocker: pytest_mock.MockerFixture,
+):
+    mocker.patch.dict(sys.modules, {'uv': None})
+    mocker.patch('shutil.which', return_value=None)
+
+    with pytest.raises(RuntimeError, match='uv executable not found'):
+        with build.env.DefaultIsolatedEnv(installer='uv'):
+            pass