Skip over broken tool Python on Windows too (#17176)

Fixes #16252

crates/uv-python/src/discovery.rs

@@ -42,7 +42,7 @@ use crate::virtualenv::{
 };
 #[cfg(windows)]
 use crate::windows_registry::{WindowsPython, registry_pythons};
-use crate::{BrokenSymlink, Interpreter, PythonVersion};
+use crate::{BrokenLink, Interpreter, PythonVersion};
 
 /// A request to find a Python installation.
 ///
@@ -1055,7 +1055,7 @@ impl Error {
                     false
                 }
                 InterpreterError::NotFound(path)
-                | InterpreterError::BrokenSymlink(BrokenSymlink { path, .. }) => {
+                | InterpreterError::BrokenLink(BrokenLink { path, .. }) => {
                     // If the interpreter is from an active, valid virtual environment, we should
                     // fail because it's broken
                     if matches!(source, PythonSource::ActiveEnvironment)
@@ -1130,7 +1130,7 @@ pub fn find_python_installations<'a>(
                 debug!("Checking for Python interpreter at {request}");
                 match python_installation_from_executable(path, cache) {
                     Ok(installation) => Ok(Ok(installation)),
-                    Err(InterpreterError::NotFound(_) | InterpreterError::BrokenSymlink(_)) => {
+                    Err(InterpreterError::NotFound(_) | InterpreterError::BrokenLink(_)) => {
                         Ok(Err(PythonNotFound {
                             request: request.clone(),
                             python_preference: preference,
@@ -1156,7 +1156,7 @@ pub fn find_python_installations<'a>(
                 debug!("Checking for Python interpreter in {request}");
                 match python_installation_from_directory(path, cache) {
                     Ok(installation) => Ok(Ok(installation)),
-                    Err(InterpreterError::NotFound(_) | InterpreterError::BrokenSymlink(_)) => {
+                    Err(InterpreterError::NotFound(_) | InterpreterError::BrokenLink(_)) => {
                         Ok(Err(PythonNotFound {
                             request: request.clone(),
                             python_preference: preference,

crates/uv-python/src/interpreter.rs

@@ -32,8 +32,8 @@ use crate::implementation::LenientImplementationName;
 use crate::managed::ManagedPythonInstallations;
 use crate::pointer_size::PointerSize;
 use crate::{
-    Prefix, PythonInstallationKey, PythonVariant, PythonVersion, Target, VersionRequest,
-    VirtualEnvironment,
+    Prefix, PyVenvConfiguration, PythonInstallationKey, PythonVariant, PythonVersion, Target,
+    VersionRequest, VirtualEnvironment,
 };
 
 #[cfg(windows)]
@@ -824,7 +824,7 @@ pub enum Error {
     #[error("Failed to query Python interpreter")]
     Io(#[from] io::Error),
     #[error(transparent)]
-    BrokenSymlink(BrokenSymlink),
+    BrokenLink(BrokenLink),
     #[error("Python interpreter not found at `{0}`")]
     NotFound(PathBuf),
     #[error("Failed to query Python interpreter at `{path}`")]
@@ -861,19 +861,30 @@ pub enum Error {
 }
 
 #[derive(Debug, Error)]
-pub struct BrokenSymlink {
+pub struct BrokenLink {
     pub path: PathBuf,
+    /// Whether we have a broken symlink (Unix) or whether the shim returned that the underlying
+    /// Python went away (Windows).
+    pub unix: bool,
     /// Whether the interpreter path looks like a virtual environment.
     pub venv: bool,
 }
 
-impl Display for BrokenSymlink {
+impl Display for BrokenLink {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
-        write!(
-            f,
-            "Broken symlink at `{}`, was the underlying Python interpreter removed?",
-            self.path.user_display()
-        )?;
+        if self.unix {
+            write!(
+                f,
+                "Broken symlink at `{}`, was the underlying Python interpreter removed?",
+                self.path.user_display()
+            )?;
+        } else {
+            write!(
+                f,
+                "Broken Python trampoline at `{}`, was the underlying Python interpreter removed?",
+                self.path.user_display()
+            )?;
+        }
         if self.venv {
             write!(
                 f,
@@ -994,6 +1005,19 @@ impl InterpreterInfo {
         if !output.status.success() {
             let stderr = String::from_utf8_lossy(&output.stderr).trim().to_string();
 
+            // Handle uninstalled CPython interpreters on Windows.
+            //
+            // The IO error from the CPython trampoline is unstructured and localized, so we check
+            // whether the `home` from `pyvenv.cfg` still exists, it's missing if the Python
+            // interpreter was uninstalled.
+            if python_home(interpreter).is_some_and(|home| !home.exists()) {
+                return Err(Error::BrokenLink(BrokenLink {
+                    path: interpreter.to_path_buf(),
+                    unix: false,
+                    venv: uv_fs::is_virtualenv_executable(interpreter),
+                }));
+            }
+
             // If the Python version is too old, we may not even be able to invoke the query script
             if stderr.contains("Unknown option: -I") {
                 return Err(Error::QueryScript {
@@ -1092,8 +1116,9 @@ impl InterpreterInfo {
                     .symlink_metadata()
                     .is_ok_and(|metadata| metadata.is_symlink())
                 {
-                    Error::BrokenSymlink(BrokenSymlink {
+                    Error::BrokenLink(BrokenLink {
                         path: executable.to_path_buf(),
+                        unix: true,
                         venv: uv_fs::is_virtualenv_executable(executable),
                     })
                 } else {
@@ -1273,6 +1298,13 @@ fn find_base_python(
     }
 }
 
+/// Parse the `home` key from `pyvenv.cfg`, if any.
+fn python_home(interpreter: &Path) -> Option<PathBuf> {
+    let venv_root = interpreter.parent()?.parent()?;
+    let pyvenv_cfg = PyVenvConfiguration::parse(venv_root.join("pyvenv.cfg")).ok()?;
+    pyvenv_cfg.home
+}
+
 #[cfg(unix)]
 #[cfg(test)]
 mod tests {

crates/uv-python/src/lib.rs

@@ -17,7 +17,7 @@ pub use crate::installation::{
     PythonInstallation, PythonInstallationKey, PythonInstallationMinorVersionKey,
 };
 pub use crate::interpreter::{
-    BrokenSymlink, Error as InterpreterError, Interpreter, canonicalize_executable,
+    BrokenLink, Error as InterpreterError, Interpreter, canonicalize_executable,
 };
 pub use crate::pointer_size::PointerSize;
 pub use crate::prefix::Prefix;

crates/uv-python/src/virtualenv.rs

@@ -34,6 +34,8 @@ pub struct VirtualEnvironment {
 /// A parsed `pyvenv.cfg`
 #[derive(Debug, Clone)]
 pub struct PyVenvConfiguration {
+    /// The `PYTHONHOME` directory containing the base Python executable.
+    pub(crate) home: Option<PathBuf>,
     /// Was the virtual environment created with the `virtualenv` package?
     pub(crate) virtualenv: bool,
     /// Was the virtual environment created with the `uv` package?
@@ -231,6 +233,7 @@ pub(crate) fn virtualenv_python_executable(venv: impl AsRef<Path>) -> PathBuf {
 impl PyVenvConfiguration {
     /// Parse a `pyvenv.cfg` file into a [`PyVenvConfiguration`].
     pub fn parse(cfg: impl AsRef<Path>) -> Result<Self, Error> {
+        let mut home = None;
         let mut virtualenv = false;
         let mut uv = false;
         let mut relocatable = false;
@@ -248,6 +251,9 @@ impl PyVenvConfiguration {
                 continue;
             };
             match key.trim() {
+                "home" => {
+                    home = Some(PathBuf::from(value.trim()));
+                }
                 "virtualenv" => {
                     virtualenv = true;
                 }
@@ -274,6 +280,7 @@ impl PyVenvConfiguration {
         }
 
         Ok(Self {
+            home,
             virtualenv,
             uv,
             relocatable,