Avoid deleting the project environment directory if it is not a virtu…

…al environment

crates/uv/src/commands/project/mod.rs

@@ -120,6 +120,9 @@ pub(crate) enum ProjectError {
  #[error("Environment marker is empty")]
  EmptyEnvironment,
 
+ #[error("Project virtual environment directory `{0}` cannot be used because it has existing, non-virtual environment content")]
+ InvalidProjectEnvironmentDir(PathBuf),
+
  #[error("Failed to parse `pyproject.toml`")]
  TomlParse(#[source] toml::de::Error),
 
@@ -488,6 +491,14 @@ pub(crate) async fn get_or_init_environment(
  FoundInterpreter::Interpreter(interpreter) => {
  let venv = workspace.venv();
 
+ // Before deleting the target directory, we confirm that it is either (1) a virtual
+ // environment or (2) an empty directory.
+ if PythonEnvironment::from_root(&venv, cache).is_err()
+ && fs_err::read_dir(&venv).is_ok_and(|mut dir| dir.next().is_some())
+ {
+ return Err(ProjectError::InvalidProjectEnvironmentDir(venv));
+ }
+
  // Remove the existing virtual environment if it doesn't meet the requirements.
  match fs_err::remove_dir_all(&venv) {
  Ok(()) => {

crates/uv/tests/sync.rs

@@ -1613,7 +1613,9 @@ fn convert_to_package() -> Result<()> {
 
 #[test]
 fn sync_custom_environment_path() -> Result<()> {
- let mut context = TestContext::new("3.12");
+ let mut context = TestContext::new_with_versions(&["3.11", "3.12"])
+ .with_filtered_virtualenv_bin()
+ .with_filtered_python_names();
 
  let pyproject_toml = context.temp_dir.child("pyproject.toml");
  pyproject_toml.write_str(
@@ -1633,6 +1635,8 @@ fn sync_custom_environment_path() -> Result<()> {
  ----- stdout -----
 
  ----- stderr -----
+ Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+ Creating virtualenv at: .venv
  Resolved 2 packages in [TIME]
  Prepared 1 package in [TIME]
  Installed 1 package in [TIME]
@@ -1733,6 +1737,52 @@ fn sync_custom_environment_path() -> Result<()> {
  .child(".venv")
  .assert(predicate::path::is_dir());
 
+ // If the directory already exists and is not a virtual environment we should fail with an error
+ fs_err::remove_dir_all(context.temp_dir.join("foo"))?;
+ fs_err::create_dir(context.temp_dir.join("foo"))?;
+ fs_err::write(context.temp_dir.join("foo").join("file"), b"")?;
+ uv_snapshot!(context.filters(), context.sync().env("UV_PROJECT_ENVIRONMENT", "foo"), @r###"
+ success: false
+ exit_code: 2
+ ----- stdout -----
+
+ ----- stderr -----
+ warning: Ignoring existing virtual environment linked to non-existent Python interpreter: foo/[BIN]/python
+ Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+ error: Project virtual environment directory `[TEMP_DIR]/foo` cannot be used because it has existing, non-virtual environment content
+ "###);
+
+ // But if it's just an incompatible virtual environment...
+ fs_err::remove_dir_all(context.temp_dir.join("foo"))?;
+ uv_snapshot!(context.filters(), context.venv().arg("foo").arg("--python").arg("3.11"), @r###"
+ success: true
+ exit_code: 0
+ ----- stdout -----
+
+ ----- stderr -----
+ Using Python 3.11.[X] interpreter at: [PYTHON-3.11]
+ Creating virtualenv at: foo
+ Activate with: source foo/[BIN]/activate
+ "###);
+
+ // Even with some extraneous content...
+ fs_err::write(context.temp_dir.join("foo").join("file"), b"")?;
+
+ // We can delete and use it
+ uv_snapshot!(context.filters(), context.sync().env("UV_PROJECT_ENVIRONMENT", "foo"), @r###"
+ success: true
+ exit_code: 0
+ ----- stdout -----
+
+ ----- stderr -----
+ Using Python 3.12.[X] interpreter at: [PYTHON-3.12]
+ Removed virtual environment at: foo
+ Creating virtualenv at: foo
+ Resolved 2 packages in [TIME]
+ Installed 1 package in [TIME]
+ + iniconfig==2.0.0
+ "###);
+
  Ok(())
 }