Replace tool environments on updated Python request (#4746)

## Summary

Closes #4741.

crates/uv-tool/src/lib.rs

@@ -147,6 +147,10 @@ impl InstalledTools {
     /// Remove the environment for a tool.
     ///
     /// Does not remove the tool's entrypoints.
+    ///
+    /// # Errors
+    ///
+    /// If no such environment exists for the tool.
     pub fn remove_environment(&self, name: &PackageName) -> Result<(), Error> {
         let _lock = self.acquire_lock();
         let environment_path = self.root.join(name.to_string());
@@ -161,23 +165,45 @@ impl InstalledTools {
         Ok(())
     }
 
-    /// Return the [`PythonEnvironment`] for a given tool.
-    pub fn environment(
+    /// Return the [`PythonEnvironment`] for a given tool, if it exists.
+    pub fn get_environment(
         &self,
         name: &PackageName,
-        remove_existing: bool,
-        interpreter: Interpreter,
         cache: &Cache,
-    ) -> Result<PythonEnvironment, Error> {
+    ) -> Result<Option<PythonEnvironment>, Error> {
         let _lock = self.acquire_lock();
         let environment_path = self.root.join(name.to_string());
 
-        if !remove_existing && environment_path.exists() {
+        if environment_path.is_dir() {
             debug!(
                 "Using existing environment for tool `{name}` at `{}`.",
                 environment_path.user_display()
             );
-            return Ok(PythonEnvironment::from_root(environment_path, cache)?);
+            Ok(Some(PythonEnvironment::from_root(environment_path, cache)?))
+        } else {
+            Ok(None)
+        }
+    }
+
+    /// Create the [`PythonEnvironment`] for a given tool, removing any existing environments.
+    pub fn create_environment(
+        &self,
+        name: &PackageName,
+        interpreter: Interpreter,
+    ) -> Result<PythonEnvironment, Error> {
+        let _lock = self.acquire_lock();
+        let environment_path = self.root.join(name.to_string());
+
+        // Remove any existing environment.
+        match fs_err::remove_dir_all(&environment_path) {
+            Ok(()) => {
+                debug!(
+                    "Removed existing environment for tool `{name}` at `{}`.",
+                    environment_path.user_display()
+                );
+            }
+            Err(err) if err.kind() == io::ErrorKind::NotFound => (),
+            Err(err) => return Err(err.into()),
         }
 
         debug!(

crates/uv/src/commands/tool/install.rs

@@ -56,8 +56,12 @@ pub(crate) async fn install(
         .connectivity(connectivity)
         .native_tls(native_tls);
 
+    let python_request = python.as_deref().map(ToolchainRequest::parse);
+
+    // Pre-emptively identify a Python interpreter. We need an interpreter to resolve any unnamed
+    // requirements, even if we end up using a different interpreter for the tool install itself.
     let interpreter = Toolchain::find_or_fetch(
-        python.as_deref().map(ToolchainRequest::parse),
+        python_request.clone(),
         EnvironmentPreference::OnlySystem,
         toolchain_preference,
         toolchain_fetch,
@@ -147,21 +151,42 @@ pub(crate) async fn install(
 
     let installed_tools = InstalledTools::from_settings()?;
     let existing_tool_receipt = installed_tools.get_tool_receipt(&from.name)?;
+    let existing_environment =
+        installed_tools
+            .get_environment(&from.name, cache)?
+            .filter(|environment| {
+                python_request.as_ref().map_or(true, |python_request| {
+                    if python_request.satisfied(environment.interpreter(), cache) {
+                        debug!("Found existing environment for tool `{}`", from.name);
+                        true
+                    } else {
+                        let _ = writeln!(
+                            printer.stderr(),
+                            "Existing environment for `{}` does not satisfy the requested Python interpreter: `{}`",
+                            from.name,
+                            python_request
+                        );
+                        false
+                    }
+                })
+            });
 
     // If the requested and receipt requirements are the same...
-    if let Some(tool_receipt) = existing_tool_receipt.as_ref() {
-        let receipt = tool_receipt
-            .requirements()
-            .iter()
-            .cloned()
-            .map(Requirement::from)
-            .collect::<Vec<_>>();
-        if requirements == receipt {
-            // And the user didn't request a reinstall or upgrade...
-            if !force && settings.reinstall.is_none() && settings.upgrade.is_none() {
-                // We're done.
-                writeln!(printer.stderr(), "Tool `{from}` is already installed")?;
-                return Ok(ExitStatus::Failure);
+    if existing_environment.is_some() {
+        if let Some(tool_receipt) = existing_tool_receipt.as_ref() {
+            let receipt = tool_receipt
+                .requirements()
+                .iter()
+                .cloned()
+                .map(Requirement::from)
+                .collect::<Vec<_>>();
+            if requirements == receipt {
+                // And the user didn't request a reinstall or upgrade...
+                if !force && settings.reinstall.is_none() && settings.upgrade.is_none() {
+                    // We're done.
+                    writeln!(printer.stderr(), "Tool `{from}` is already installed")?;
+                    return Ok(ExitStatus::Failure);
+                }
             }
         }
     }
@@ -171,9 +196,15 @@ pub(crate) async fn install(
     // entrypoints (without `--force`).
     let reinstall_entry_points = existing_tool_receipt.is_some();
 
-    // TODO(zanieb): Build the environment in the cache directory then copy into the tool directory
-    // This lets us confirm the environment is valid before removing an existing install
-    let environment = installed_tools.environment(&from.name, force, interpreter, cache)?;
+    // TODO(zanieb): Build the environment in the cache directory then copy into the tool directory.
+    // This lets us confirm the environment is valid before removing an existing install. However,
+    // entrypoints always contain an absolute path to the relevant Python interpreter, which would
+    // be invalidated by moving the environment.
+    let environment = if let Some(environment) = existing_environment {
+        environment
+    } else {
+        installed_tools.create_environment(&from.name, interpreter)?
+    };
 
     // Install the ephemeral requirements.
     let spec = RequirementsSpecification::from_requirements(requirements.clone());

crates/uv/tests/tool_install.rs

@@ -648,14 +648,6 @@ fn tool_install_entry_point_exists() {
 
     ----- stderr -----
     warning: `uv tool install` is experimental and may change without warning.
-    Resolved [N] packages in [TIME]
-    Installed [N] packages in [TIME]
-     + black==24.3.0
-     + click==8.1.7
-     + mypy-extensions==1.0.0
-     + packaging==24.0
-     + pathspec==0.12.1
-     + platformdirs==4.2.0
     Installed: black, blackd
     "###);
 
@@ -1329,3 +1321,80 @@ fn tool_install_upgrade() {
         "###);
     });
 }
+
+/// Test reinstalling tools with varying `--python` requests.
+#[test]
+fn tool_install_python_request() {
+    let context = TestContext::new_with_versions(&["3.11", "3.12"])
+        .with_filtered_counts()
+        .with_filtered_exe_suffix();
+    let tool_dir = context.temp_dir.child("tools");
+    let bin_dir = context.temp_dir.child("bin");
+
+    // Install `black`.
+    uv_snapshot!(context.filters(), context.tool_install()
+        .arg("-p")
+        .arg("3.12")
+        .arg("black")
+        .env("UV_TOOL_DIR", tool_dir.as_os_str())
+        .env("XDG_BIN_HOME", bin_dir.as_os_str()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: `uv tool install` is experimental and may change without warning.
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     + black==24.3.0
+     + click==8.1.7
+     + mypy-extensions==1.0.0
+     + packaging==24.0
+     + pathspec==0.12.1
+     + platformdirs==4.2.0
+    Installed: black, blackd
+    "###);
+
+    // Install with Python 3.12 (compatible).
+    uv_snapshot!(context.filters(), context.tool_install()
+        .arg("-p")
+        .arg("3.12")
+        .arg("black")
+        .env("UV_TOOL_DIR", tool_dir.as_os_str())
+        .env("XDG_BIN_HOME", bin_dir.as_os_str()), @r###"
+    success: false
+    exit_code: 1
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: `uv tool install` is experimental and may change without warning.
+    Tool `black` is already installed
+    "###);
+
+    // Install with Python 3.11 (incompatible).
+    uv_snapshot!(context.filters(), context.tool_install()
+        .arg("-p")
+        .arg("3.11")
+        .arg("black")
+        .env("UV_TOOL_DIR", tool_dir.as_os_str())
+        .env("XDG_BIN_HOME", bin_dir.as_os_str()), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    warning: `uv tool install` is experimental and may change without warning.
+    Existing environment for `black` does not satisfy the requested Python interpreter: `Python 3.11`
+    Resolved [N] packages in [TIME]
+    Prepared [N] packages in [TIME]
+    Installed [N] packages in [TIME]
+     + black==24.3.0
+     + click==8.1.7
+     + mypy-extensions==1.0.0
+     + packaging==24.0
+     + pathspec==0.12.1
+     + platformdirs==4.2.0
+    Installed: black, blackd
+    "###);
+}