From 8c363e38844354ba7f50531c0aea5bc53affa6c8 Mon Sep 17 00:00:00 2001
From: Zanie Blue <contact@zanie.dev>
Date: Sat, 7 Dec 2024 10:48:30 -0600
Subject: [PATCH] Replace executables with broken symlinks during `uv python
 install`

---
 crates/uv/src/commands/python/install.rs | 63 ++++++++++++++++--------
 crates/uv/tests/it/python_install.rs     | 37 ++++++++++++++
 2 files changed, 79 insertions(+), 21 deletions(-)

diff --git a/crates/uv/src/commands/python/install.rs b/crates/uv/src/commands/python/install.rs
index 9905903de8e9f..4051d4a1daf11 100644
--- a/crates/uv/src/commands/python/install.rs
+++ b/crates/uv/src/commands/python/install.rs
@@ -354,32 +354,53 @@ pub(crate) async fn install(
                         target.simplified_display()
                     );
 
-                    // Figure out what installation it references, if any
-                    let existing = find_matching_bin_link(
-                        installations
-                            .iter()
-                            .copied()
-                            .chain(existing_installations.iter()),
-                        &target,
-                    );
+                    // Check if the existing link is valid
+                    let valid_link = match target.read_link().and_then(|target| target.try_exists())
+                    {
+                        Ok(valid) => valid,
+                        Err(err) => {
+                            debug!("Failed to inspect executable with error: {err}");
+                            true // Treat this as a valid link, we won't remove it without `--force`
+                        }
+                    };
+
+                    // Figure out what installation it references, if anyf
+                    let existing = valid_link
+                        .then(|| {
+                            find_matching_bin_link(
+                                installations
+                                    .iter()
+                                    .copied()
+                                    .chain(existing_installations.iter()),
+                                &target,
+                            )
+                        })
+                        .flatten();
 
                     match existing {
                         None => {
                             // There's an existing executable we don't manage, require `--force`
-                            if !force {
-                                errors.push((
-                                    installation.key(),
-                                    anyhow::anyhow!(
-                                        "Executable already exists at `{}` but is not managed by uv; use `--force` to replace it",
-                                        to.simplified_display()
-                                    ),
-                                ));
-                                continue;
+                            if valid_link {
+                                if !force {
+                                    errors.push((
+                                        installation.key(),
+                                        anyhow::anyhow!(
+                                            "Executable already exists at `{}` but is not managed by uv; use `--force` to replace it",
+                                            to.simplified_display()
+                                        ),
+                                    ));
+                                    continue;
+                                }
+                                debug!(
+                                    "Replacing existing executable at `{}` due to `--force`",
+                                    target.simplified_display()
+                                );
+                            } else {
+                                debug!(
+                                    "Replacing existing executable at `{}` due to an invalid symlink",
+                                    target.simplified_display()
+                                );
                             }
-                            debug!(
-                                "Replacing existing executable at `{}` due to `--force`",
-                                target.simplified_display()
-                            );
                         }
                         Some(existing) if existing == *installation => {
                             // The existing link points to the same installation, so we're done unless
diff --git a/crates/uv/tests/it/python_install.rs b/crates/uv/tests/it/python_install.rs
index 5094a0b4209f4..082ae65f6b21b 100644
--- a/crates/uv/tests/it/python_install.rs
+++ b/crates/uv/tests/it/python_install.rs
@@ -812,3 +812,40 @@ fn read_link_path(path: &Path) -> String {
         unreachable!()
     }
 }
+
+#[test]
+#[cfg(unix)]
+fn python_install_preview_broken_link() {
+    let context: TestContext = TestContext::new_with_versions(&[])
+        .with_filtered_python_keys()
+        .with_filtered_exe_suffix();
+
+    let bin_python = context.temp_dir.child("bin").child(format!("python3.13"));
+
+    use assert_fs::prelude::PathCreateDir;
+    use fs_err::os::unix::fs::symlink;
+
+    // Create a broken symlink
+    context.temp_dir.child("bin").create_dir_all().unwrap();
+    symlink(&context.temp_dir.join("does-not-exist"), &bin_python).unwrap();
+
+    // Install
+    uv_snapshot!(context.filters(), context.python_install().arg("--preview").arg("3.13"), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Installed Python 3.13.1 in [TIME]
+     + cpython-3.13.1-[PLATFORM] (python3.13)
+    "###);
+
+    // We should replace the broken symlink
+    insta::with_settings!({
+        filters => context.filters(),
+    }, {
+        insta::assert_snapshot!(
+            read_link_path(&bin_python), @"[TEMP_DIR]/managed/cpython-3.13.1-[PLATFORM]/bin/python3.13"
+        );
+    });
+}