Merge c07e98de74 into f609e1ddaf

crates/uv-python/src/discovery.rs

@@ -52,6 +52,8 @@ pub enum PythonRequest {
     /// Any Python installation
     Any,
     /// A Python version without an implementation name e.g. `3.10` or `>=3.12,<3.13`
+    Latest,
+    // Newest resolvable, stable Python version.
     Version(VersionRequest),
     /// A path to a directory containing a Python installation, e.g. `.venv`
     Directory(PathBuf),
@@ -181,6 +183,7 @@ pub enum VersionRequest {
     Default,
     /// Allow any Python version.
     Any,
+    Latest,
     Major(u8, PythonVariant),
     MajorMinor(u8, u8, PythonVariant),
     MajorMinorPatch(u8, u8, u8, PythonVariant),
@@ -624,6 +627,7 @@ fn find_all_minor(
     match version_request {
         &VersionRequest::Any
         | VersionRequest::Default
+        | VersionRequest::Latest
         | VersionRequest::Major(_, _)
         | VersionRequest::Range(_, _) => {
             let regex = if let Some(implementation) = implementation {
@@ -1135,6 +1139,19 @@ pub fn find_python_installations<'a>(
                 .map_ok(|tuple| Ok(PythonInstallation::from_tuple(tuple)))
             })
         }
+        PythonRequest::Latest => Box::new({
+            debug!("Searching for latest Python interpreter in {sources}");
+            python_interpreters(&VersionRequest::Any, None, environments, preference, cache)
+                .filter_ok(|(_source, interpreter)| interpreter.python_version().pre().is_none())
+                .max_by(|a, b| match (a.as_ref(), b.as_ref()) {
+                    (Ok((_, interpreter_a)), Ok((_, interpreter_b))) => {
+                        interpreter_a.key().cmp(&interpreter_b.key())
+                    }
+                    _ => std::cmp::Ordering::Equal,
+                })
+                .into_iter()
+                .map_ok(|tuple| Ok(PythonInstallation::from_tuple(tuple)))
+        }),
     }
 }
 
@@ -1673,9 +1690,7 @@ impl PythonRequest {
         // parsing errors are raised to the caller.
         if let Some(after_at) = rest.strip_prefix('@') {
             if after_at == "latest" {
-                // Handle `@latest` as a special case. It's still an error for now, but we plan to
-                // support it. TODO(zanieb): Add `PythonRequest::Latest`
-                return Err(Error::LatestVersionRequest);
+                return Ok(Some(VersionRequest::Latest));
             }
             return after_at.parse().map(Some);
         }
@@ -1710,7 +1725,7 @@ impl PythonRequest {
         }
 
         match self {
-            PythonRequest::Default | PythonRequest::Any => true,
+            PythonRequest::Default | PythonRequest::Any | PythonRequest::Latest => true,
             PythonRequest::Version(version_request) => {
                 version_request.matches_interpreter(interpreter)
             }
@@ -1799,7 +1814,7 @@ impl PythonRequest {
     /// Whether this request opts-in to a pre-release Python version.
     pub(crate) fn allows_prereleases(&self) -> bool {
         match self {
-            Self::Default => false,
+            Self::Default | Self::Latest => false,
             Self::Any => true,
             Self::Version(version) => version.allows_prereleases(),
             Self::Directory(_) | Self::File(_) | Self::ExecutableName(_) => true,
@@ -1812,7 +1827,7 @@ impl PythonRequest {
     /// Whether this request opts-in to an alternative Python implementation, e.g., PyPy.
     pub(crate) fn allows_alternative_implementations(&self) -> bool {
         match self {
-            Self::Default => false,
+            Self::Default | Self::Latest => false,
             Self::Any => true,
             Self::Version(_) => false,
             Self::Directory(_) | Self::File(_) | Self::ExecutableName(_) => true,
@@ -1833,6 +1848,7 @@ impl PythonRequest {
         match self {
             Self::Any => "any".to_string(),
             Self::Default => "default".to_string(),
+            Self::Latest => "latest".to_string(),
             Self::Version(version) => version.to_string(),
             Self::Directory(path) => path.display().to_string(),
             Self::File(path) => path.display().to_string(),
@@ -2238,7 +2254,7 @@ impl VersionRequest {
     /// Return the major version segment of the request, if any.
     pub(crate) fn major(&self) -> Option<u8> {
         match self {
-            Self::Any | Self::Default | Self::Range(_, _) => None,
+            Self::Any | Self::Default | Self::Latest | Self::Range(_, _) => None,
             Self::Major(major, _) => Some(*major),
             Self::MajorMinor(major, _, _) => Some(*major),
             Self::MajorMinorPatch(major, _, _, _) => Some(*major),
@@ -2249,7 +2265,7 @@ impl VersionRequest {
     /// Return the minor version segment of the request, if any.
     pub(crate) fn minor(&self) -> Option<u8> {
         match self {
-            Self::Any | Self::Default | Self::Range(_, _) => None,
+            Self::Any | Self::Default | Self::Latest | Self::Range(_, _) => None,
             Self::Major(_, _) => None,
             Self::MajorMinor(_, minor, _) => Some(*minor),
             Self::MajorMinorPatch(_, minor, _, _) => Some(*minor),
@@ -2260,7 +2276,7 @@ impl VersionRequest {
     /// Return the patch version segment of the request, if any.
     pub(crate) fn patch(&self) -> Option<u8> {
         match self {
-            Self::Any | Self::Default | Self::Range(_, _) => None,
+            Self::Any | Self::Default | Self::Latest | Self::Range(_, _) => None,
             Self::Major(_, _) => None,
             Self::MajorMinor(_, _, _) => None,
             Self::MajorMinorPatch(_, _, patch, _) => Some(*patch),
@@ -2273,7 +2289,7 @@ impl VersionRequest {
     /// If not, an `Err` is returned with an explanatory message.
     pub(crate) fn check_supported(&self) -> Result<(), String> {
         match self {
-            Self::Any | Self::Default => (),
+            Self::Any | Self::Latest | Self::Default => (),
             Self::Major(major, _) => {
                 if *major < 3 {
                     return Err(format!(
@@ -2348,6 +2364,7 @@ impl VersionRequest {
     pub(crate) fn matches_interpreter(&self, interpreter: &Interpreter) -> bool {
         match self {
             Self::Any => true,
+            Self::Latest => interpreter.python_version().pre().is_none(),
             // Do not use free-threaded interpreters by default
             Self::Default => PythonVariant::Default.matches_interpreter(interpreter),
             Self::Major(major, variant) => {
@@ -2391,6 +2408,7 @@ impl VersionRequest {
     pub(crate) fn matches_version(&self, version: &PythonVersion) -> bool {
         match self {
             Self::Any | Self::Default => true,
+            Self::Latest => version.pre().is_none(),
             Self::Major(major, _) => version.major() == *major,
             Self::MajorMinor(major, minor, _) => {
                 (version.major(), version.minor()) == (*major, *minor)
@@ -2413,7 +2431,7 @@ impl VersionRequest {
     /// avoid querying interpreters if it's clear it cannot fulfill the request.
     fn matches_major_minor(&self, major: u8, minor: u8) -> bool {
         match self {
-            Self::Any | Self::Default => true,
+            Self::Any | Self::Latest | Self::Default => true,
             Self::Major(self_major, _) => *self_major == major,
             Self::MajorMinor(self_major, self_minor, _) => {
                 (*self_major, *self_minor) == (major, minor)
@@ -2460,6 +2478,7 @@ impl VersionRequest {
     ) -> bool {
         match self {
             Self::Any | Self::Default => true,
+            Self::Latest => prerelease.is_none(),
             Self::Major(self_major, _) => *self_major == major,
             Self::MajorMinor(self_major, self_minor, _) => {
                 (*self_major, *self_minor) == (major, minor)
@@ -2482,7 +2501,7 @@ impl VersionRequest {
     /// Whether a patch version segment is present in the request.
     fn has_patch(&self) -> bool {
         match self {
-            Self::Any | Self::Default => false,
+            Self::Any | Self::Default | Self::Latest => false,
             Self::Major(..) => false,
             Self::MajorMinor(..) => false,
             Self::MajorMinorPatch(..) => true,
@@ -2499,6 +2518,7 @@ impl VersionRequest {
         match self {
             Self::Default => Self::Default,
             Self::Any => Self::Any,
+            Self::Latest => Self::Latest,
             Self::Major(major, variant) => Self::Major(major, variant),
             Self::MajorMinor(major, minor, variant) => Self::MajorMinor(major, minor, variant),
             Self::MajorMinorPatch(major, minor, _, variant) => {
@@ -2514,7 +2534,7 @@ impl VersionRequest {
     /// Whether this request should allow selection of pre-release versions.
     pub(crate) fn allows_prereleases(&self) -> bool {
         match self {
-            Self::Default => false,
+            Self::Default | Self::Latest => false,
             Self::Any => true,
             Self::Major(..) => false,
             Self::MajorMinor(..) => false,
@@ -2527,7 +2547,7 @@ impl VersionRequest {
     /// Whether this request is for a free-threaded Python variant.
     pub(crate) fn is_freethreaded(&self) -> bool {
         match self {
-            Self::Any | Self::Default => false,
+            Self::Any | Self::Default | Self::Latest => false,
             Self::Major(_, variant)
             | Self::MajorMinor(_, _, variant)
             | Self::MajorMinorPatch(_, _, _, variant)
@@ -2544,7 +2564,7 @@ impl VersionRequest {
         // TODO(zanieb): Replace this entire function with a utility that casts this to a version
         // without using `VersionRequest::to_string`.
         match self {
-            Self::Any | Self::Default => self,
+            Self::Any | Self::Default | Self::Latest => self,
             Self::Major(major, _) => Self::Major(major, PythonVariant::Default),
             Self::MajorMinor(major, minor, _) => {
                 Self::MajorMinor(major, minor, PythonVariant::Default)
@@ -2563,7 +2583,7 @@ impl VersionRequest {
     pub(crate) fn variant(&self) -> Option<PythonVariant> {
         match self {
             Self::Any => None,
-            Self::Default => Some(PythonVariant::Default),
+            Self::Default | Self::Latest => Some(PythonVariant::Default),
             Self::Major(_, variant)
             | Self::MajorMinor(_, _, variant)
             | Self::MajorMinorPatch(_, _, _, variant)
@@ -2578,7 +2598,7 @@ impl FromStr for VersionRequest {
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         // Stripping the 't' suffix produces awkward error messages if the user tries a version
-        // like "latest". HACK: If the version is all letters, don't even try to parse it further.
+        // like "oldest". HACK: If the version is all letters, don't even try to parse it further.
         if s.chars().all(char::is_alphabetic) {
             return Err(Error::InvalidVersionRequest(s.to_string()));
         }
@@ -2718,6 +2738,7 @@ impl fmt::Display for VersionRequest {
         match self {
             Self::Any => f.write_str("any"),
             Self::Default => f.write_str("default"),
+            Self::Latest => f.write_str("latest"),
             Self::Major(major, PythonVariant::Default) => write!(f, "{major}"),
             Self::Major(major, PythonVariant::Freethreaded) => write!(f, "{major}t"),
             Self::MajorMinor(major, minor, PythonVariant::Default) => write!(f, "{major}.{minor}"),
@@ -2746,6 +2767,7 @@ impl fmt::Display for PythonRequest {
         match self {
             Self::Default => write!(f, "a default Python"),
             Self::Any => write!(f, "any Python"),
+            Self::Latest => write!(f, "latest stable Python"),
             Self::Version(version) => write!(f, "Python {version}"),
             Self::Directory(path) => write!(f, "directory `{}`", path.user_display()),
             Self::File(path) => write!(f, "path `{}`", path.user_display()),

crates/uv-python/src/downloads.rs

@@ -316,7 +316,7 @@ impl PythonDownloadRequest {
                 prereleases: Some(true), // Explicitly allow pre-releases for PythonRequest::Any
                 ..Self::default()
             }),
-            PythonRequest::Default => Some(Self::default()),
+            PythonRequest::Default | PythonRequest::Latest => Some(Self::default()),
             // We can't download a managed installation for these request kinds
             PythonRequest::Directory(_)
             | PythonRequest::ExecutableName(_)

crates/uv-python/src/lib.rs

@@ -1061,6 +1061,106 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn find_python_latest() -> Result<()> {
+        let mut context = TestContext::new()?;
+        context.add_python_versions(&["3.8.10", "3.11.5", "3.9.18", "3.10.12"])?;
+
+        let python = context.run(|| {
+            find_python_installation(
+                &PythonRequest::Latest,
+                EnvironmentPreference::Any,
+                PythonPreference::OnlySystem,
+                &context.cache,
+            )
+        })??;
+
+        assert!(
+            matches!(
+                python,
+                PythonInstallation {
+                    source: PythonSource::SearchPath,
+                    interpreter: _
+                }
+            ),
+            "We should find a python; got {python:?}"
+        );
+        assert_eq!(
+            &python.interpreter().python_full_version().to_string(),
+            "3.11.5",
+            "We should find the latest version (3.11.5)"
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn find_python_latest_with_prereleases() -> Result<()> {
+        let mut context = TestContext::new()?;
+        context.add_python_versions(&["3.10.1", "3.11.2", "3.12.0rc1", "3.13.0a1"])?;
+
+        let python = context.run(|| {
+            find_python_installation(
+                &PythonRequest::Latest,
+                EnvironmentPreference::Any,
+                PythonPreference::OnlySystem,
+                &context.cache,
+            )
+        })??;
+
+        assert_eq!(
+            &python.interpreter().python_full_version().to_string(),
+            "3.11.2",
+            "Latest should find the highest stable version"
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn find_python_latest_no_pythons() -> Result<()> {
+        let context = TestContext::new()?;
+        // Don't add any Python versions
+
+        let result = context.run(|| {
+            find_python_installation(
+                &PythonRequest::Latest,
+                EnvironmentPreference::Any,
+                PythonPreference::OnlySystem,
+                &context.cache,
+            )
+        })?;
+
+        assert!(
+            matches!(result, Err(PythonNotFound { .. })),
+            "We should not find any python when none are available; got {result:?}"
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn find_python_latest_only_prereleases() -> Result<()> {
+        let mut context = TestContext::new()?;
+        context.add_python_versions(&["3.12.0rc1", "3.13.0a1", "3.11.0b2"])?;
+
+        let result = context.run(|| {
+            find_python_installation(
+                &PythonRequest::Latest,
+                EnvironmentPreference::Any,
+                PythonPreference::OnlySystem,
+                &context.cache,
+            )
+        })?;
+
+        assert!(
+            matches!(result, Err(PythonNotFound { .. })),
+            "We should not find any python when only prereleases are available; got {result:?}"
+        );
+
+        Ok(())
+    }
+
     #[test]
     fn find_python_from_conda_prefix() -> Result<()> {
         let context = TestContext::new()?;

crates/uv-python/src/managed.rs

@@ -473,6 +473,7 @@ impl ManagedPythonInstallation {
             }
             PythonRequest::Version(version) => version.matches_version(&self.version()),
             PythonRequest::Key(request) => request.satisfied_by_key(self.key()),
+            PythonRequest::Latest => true,
         }
     }
 

crates/uv/tests/it/tool_run.rs

@@ -2039,14 +2039,15 @@ fn tool_run_python_at_version() {
     // Request `@latest` (not yet supported)
     uv_snapshot!(context.filters(), context.tool_run()
         .arg("python@latest")
-        .arg("--version"), @r###"
-    success: false
-    exit_code: 2
+        .arg("--version"), @r"
+    success: true
+    exit_code: 0
     ----- stdout -----
+    Python 3.12.[X]
 
     ----- stderr -----
-    error: Requesting the 'latest' Python version is not yet supported
-    "###);
+    Resolved in [TIME]
+    ");
 }
 
 #[test]