[ty] Infer the Python version from the environment if feasible

crates/ruff_graph/src/db.rs

@@ -44,7 +44,7 @@ impl ModuleDb {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version,
+                python_version: Some(python_version),
                 python_platform: PythonPlatform::default(),
                 search_paths,
             },

crates/ty_ide/src/inlay_hints.rs

@@ -191,7 +191,7 @@ mod tests {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::latest_ty(),
+                python_version: Some(PythonVersion::latest_ty()),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],

crates/ty_ide/src/lib.rs

@@ -228,7 +228,7 @@ mod tests {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::latest_ty(),
+                python_version: Some(PythonVersion::latest_ty()),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],

crates/ty_project/src/lib.rs

@@ -679,7 +679,7 @@ mod tests {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::default(),
+                python_version: Some(PythonVersion::default()),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings::new(vec![SystemPathBuf::from(".")]),
             },

crates/ty_project/src/metadata/options.rs

@@ -104,7 +104,7 @@ impl Options {
                 default
             });
         ProgramSettings {
-            python_version,
+            python_version: Some(python_version),
             python_platform,
             search_paths: self.to_search_path_settings(project_root, system),
         }

crates/ty_python_semantic/src/db.rs

@@ -179,7 +179,7 @@ pub(crate) mod tests {
             Program::from_settings(
                 &db,
                 ProgramSettings {
-                    python_version: self.python_version,
+                    python_version: Some(self.python_version),
                     python_platform: self.python_platform,
                     search_paths: SearchPathSettings::new(vec![src_root]),
                 },

crates/ty_python_semantic/src/module_resolver/resolver.rs

@@ -14,7 +14,7 @@ use ruff_python_ast::PythonVersion;
 use crate::db::Db;
 use crate::module_name::ModuleName;
 use crate::module_resolver::typeshed::{vendored_typeshed_versions, TypeshedVersions};
-use crate::site_packages::{PythonEnvironment, SitePackagesDiscoveryError, SysPrefixPathOrigin};
+use crate::site_packages::{PythonEnvironment, SysPrefixPathOrigin};
 use crate::{Program, PythonPath, SearchPathSettings};
 
 use super::module::{Module, ModuleKind};
@@ -160,6 +160,11 @@ pub struct SearchPaths {
     site_packages: Vec<SearchPath>,
 
     typeshed_versions: TypeshedVersions,
+
+    /// The Python version for the search paths, if any.
+    ///
+    /// This is read from the `pyvenv.cfg` if present.
+    python_version: Option<PythonVersion>,
 }
 
 impl SearchPaths {
@@ -234,7 +239,7 @@ impl SearchPaths {
 
         static_paths.push(stdlib_path);
 
-        let site_packages_paths = match python_path {
+        let (site_packages_paths, python_version) = match python_path {
             PythonPath::SysPrefix(sys_prefix, origin) => {
                 tracing::debug!(
                     "Discovering site-packages paths from sys-prefix `{sys_prefix}` ({origin}')"
@@ -243,8 +248,9 @@ impl SearchPaths {
                 //  than the one resolved in the program settings because it indicates
                 //  that the `target-version` is incorrectly configured or that the
                 //  venv is out of date.
-                PythonEnvironment::new(sys_prefix, *origin, system)
-                    .and_then(|env| env.site_packages_directories(system))?
+                PythonEnvironment::new(sys_prefix.clone(), *origin, system).and_then(|env| {
+                    Ok((env.site_packages_directories(system)?, env.python_version()))
+                })?
             }
 
             PythonPath::Resolve(target, origin) => {
@@ -270,45 +276,47 @@ impl SearchPaths {
                     // handle the error.
                     .unwrap_or(target);
 
-                PythonEnvironment::new(root, *origin, system)
-                    .and_then(|venv| venv.site_packages_directories(system))?
+                PythonEnvironment::new(root, *origin, system).and_then(|env| {
+                    Ok((env.site_packages_directories(system)?, env.python_version()))
+                })?
             }
 
             PythonPath::Discover(root) => {
                 tracing::debug!("Discovering virtual environment in `{root}`");
-                let virtual_env_path = discover_venv_in(db.system(), root);
-                if let Some(virtual_env_path) = virtual_env_path {
-                    tracing::debug!("Found `.venv` folder at `{}`", virtual_env_path);
-
-                    let handle_invalid_virtual_env = |error: SitePackagesDiscoveryError| {
-                        tracing::debug!(
-                            "Ignoring automatically detected virtual environment at `{}`: {}",
-                            virtual_env_path,
-                            error
-                        );
-                        vec![]
-                    };
-
-                    match PythonEnvironment::new(
-                        virtual_env_path.clone(),
-                        SysPrefixPathOrigin::LocalVenv,
-                        system,
-                    ) {
-                        Ok(venv) => venv
-                            .site_packages_directories(system)
-                            .unwrap_or_else(handle_invalid_virtual_env),
-                        Err(error) => handle_invalid_virtual_env(error),
-                    }
-                } else {
-                    tracing::debug!("No virtual environment found");
-                    vec![]
-                }
+                discover_venv_in(db.system(), root)
+                    .and_then(|virtual_env_path| {
+                        tracing::debug!("Found `.venv` folder at `{}`", virtual_env_path);
+
+                        PythonEnvironment::new(
+                            virtual_env_path.clone(),
+                            SysPrefixPathOrigin::LocalVenv,
+                            system,
+                        )
+                        .and_then(|env| {
+                            Ok((env.site_packages_directories(system)?, env.python_version()))
+                        })
+                        .inspect_err(|err| {
+                            tracing::debug!(
+                                "Ignoring automatically detected virtual environment at `{}`: {}",
+                                virtual_env_path,
+                                err
+                            );
+                        })
+                        .ok()
+                    })
+                    .unwrap_or_else(|| {
+                        tracing::debug!("No virtual environment found");
+                        (vec![], None)
+                    })
             }
 
-            PythonPath::KnownSitePackages(paths) => paths
-                .iter()
-                .map(|path| canonicalize(path, system))
-                .collect(),
+            PythonPath::KnownSitePackages(paths) => (
+                paths
+                    .iter()
+                    .map(|path| canonicalize(path, system))
+                    .collect(),
+                None,
+            ),
         };
 
         let mut site_packages: Vec<_> = Vec::with_capacity(site_packages_paths.len());
@@ -342,6 +350,7 @@ impl SearchPaths {
             static_paths,
             site_packages,
             typeshed_versions,
+            python_version,
         })
     }
 
@@ -366,6 +375,10 @@ impl SearchPaths {
     pub(super) fn typeshed_versions(&self) -> &TypeshedVersions {
         &self.typeshed_versions
     }
+
+    pub fn python_version(&self) -> Option<PythonVersion> {
+        self.python_version
+    }
 }
 
 /// Collect all dynamic search paths. For each `site-packages` path:
@@ -384,6 +397,7 @@ pub(crate) fn dynamic_resolution_paths(db: &dyn Db) -> Vec<SearchPath> {
         static_paths,
         site_packages,
         typeshed_versions: _,
+        python_version: _,
     } = Program::get(db).search_paths(db);
 
     let mut dynamic_paths = Vec::new();
@@ -1489,7 +1503,7 @@ mod tests {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::PY38,
+                python_version: Some(PythonVersion::PY38),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
@@ -1995,7 +2009,7 @@ not_a_directory
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::default(),
+                python_version: Some(PythonVersion::default()),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
@@ -2068,7 +2082,7 @@ not_a_directory
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::default(),
+                python_version: Some(PythonVersion::default()),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
@@ -2108,7 +2122,7 @@ not_a_directory
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version: PythonVersion::default(),
+                python_version: Some(PythonVersion::default()),
                 python_platform: PythonPlatform::default(),
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],

crates/ty_python_semantic/src/module_resolver/testing.rs

@@ -235,7 +235,7 @@ impl TestCaseBuilder<MockedTypeshed> {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version,
+                python_version: Some(python_version),
                 python_platform,
                 search_paths: SearchPathSettings {
                     extra_paths: vec![],
@@ -293,7 +293,7 @@ impl TestCaseBuilder<VendoredTypeshed> {
         Program::from_settings(
             &db,
             ProgramSettings {
-                python_version,
+                python_version: Some(python_version),
                 python_platform,
                 search_paths: SearchPathSettings {
                     python_path: PythonPath::KnownSitePackages(vec![site_packages.clone()]),

crates/ty_python_semantic/src/program.rs

@@ -28,11 +28,15 @@ impl Program {
             search_paths,
         } = settings;
 
-        tracing::info!("Python version: Python {python_version}, platform: {python_platform}");
-
         let search_paths = SearchPaths::from_settings(db, &search_paths)
             .with_context(|| "Invalid search path settings")?;
 
+        let python_version = python_version
+            .or_else(|| search_paths.python_version())
+            .unwrap_or(PythonVersion::latest_ty());
+
+        tracing::info!("Python version: Python {python_version}, platform: {python_platform}");
+
         Ok(
             Program::builder(python_version, python_platform, search_paths)
                 .durability(Durability::HIGH)
@@ -56,9 +60,11 @@ impl Program {
             self.set_python_platform(db).to(python_platform);
         }
 
-        if python_version != self.python_version(db) {
-            tracing::debug!("Updating python version: Python {python_version}");
-            self.set_python_version(db).to(python_version);
+        if let Some(python_version) = python_version {
+            if python_version != self.python_version(db) {
+                tracing::debug!("Updating python version: Python {python_version}");
+                self.set_python_version(db).to(python_version);
+            }
         }
 
         self.update_search_paths(db, &search_paths)?;
@@ -89,7 +95,7 @@ impl Program {
 #[derive(Clone, Debug, Eq, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize))]
 pub struct ProgramSettings {
-    pub python_version: PythonVersion,
+    pub python_version: Option<PythonVersion>,
     pub python_platform: PythonPlatform,
     pub search_paths: SearchPathSettings,
 }

crates/ty_python_semantic/src/site_packages.rs

@@ -60,6 +60,13 @@ impl PythonEnvironment {
             Self::System(env) => env.site_packages_directories(system),
         }
     }
+
+    pub(crate) fn python_version(&self) -> Option<PythonVersion> {
+        match self {
+            Self::Virtual(env) => env.version,
+            Self::System(_) => None,
+        }
+    }
 }
 
 /// Abstraction for a Python virtual environment.

crates/ty_test/src/assertion.rs

@@ -500,7 +500,7 @@ mod tests {
         let mut db = Db::setup();
 
         let settings = ProgramSettings {
-            python_version: PythonVersion::default(),
+            python_version: Some(PythonVersion::default()),
             python_platform: PythonPlatform::default(),
             search_paths: SearchPathSettings::new(Vec::new()),
         };

crates/ty_test/src/lib.rs

@@ -257,7 +257,7 @@ fn run_test(
     let configuration = test.configuration();
 
     let settings = ProgramSettings {
-        python_version,
+        python_version: Some(python_version),
         python_platform: configuration
             .python_platform()
             .unwrap_or(PythonPlatform::Identifier("linux".to_string())),

crates/ty_test/src/matcher.rs

@@ -384,7 +384,7 @@ mod tests {
         let mut db = crate::db::Db::setup();
 
         let settings = ProgramSettings {
-            python_version: PythonVersion::default(),
+            python_version: Some(PythonVersion::default()),
             python_platform: PythonPlatform::default(),
             search_paths: SearchPathSettings::new(Vec::new()),
         };

fuzz/fuzz_targets/ty_check_invalid_syntax.rs

@@ -118,7 +118,7 @@ fn setup_db() -> TestDb {
     Program::from_settings(
         &db,
         ProgramSettings {
-            python_version: PythonVersion::default(),
+            python_version: Some(PythonVersion::default()),
             python_platform: PythonPlatform::default(),
             search_paths: SearchPathSettings::new(vec![src_root]),
         },