red-knot[salsa part 2]: Setup semantic DB and Jar (#11837)

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

crates/ruff_python_semantic/src/db.rs

@@ -0,0 +1,91 @@
+use ruff_db::{Db as SourceDb, Upcast};
+use salsa::DbWithJar;
+
+// Salsa doesn't support a struct without fields, so allow the clippy lint for now.
+#[allow(clippy::empty_structs_with_brackets)]
+#[salsa::jar(db=Db)]
+pub struct Jar();
+
+/// Database giving access to semantic information about a Python program.
+pub trait Db: SourceDb + DbWithJar<Jar> + Upcast<dyn SourceDb> {}
+
+#[cfg(test)]
+mod tests {
+    use super::{Db, Jar};
+    use ruff_db::file_system::{FileSystem, MemoryFileSystem};
+    use ruff_db::vfs::Vfs;
+    use ruff_db::{Db as SourceDb, Jar as SourceJar, Upcast};
+    use salsa::DebugWithDb;
+
+    #[salsa::db(Jar, SourceJar)]
+    pub(crate) struct TestDb {
+        storage: salsa::Storage<Self>,
+        vfs: Vfs,
+        file_system: MemoryFileSystem,
+        events: std::sync::Arc<std::sync::Mutex<Vec<salsa::Event>>>,
+    }
+
+    impl TestDb {
+        #[allow(unused)]
+        pub(crate) fn new() -> Self {
+            Self {
+                storage: salsa::Storage::default(),
+                file_system: MemoryFileSystem::default(),
+                events: std::sync::Arc::default(),
+                vfs: Vfs::with_stubbed_vendored(),
+            }
+        }
+
+        #[allow(unused)]
+        pub(crate) fn memory_file_system(&self) -> &MemoryFileSystem {
+            &self.file_system
+        }
+
+        #[allow(unused)]
+        pub(crate) fn memory_file_system_mut(&mut self) -> &mut MemoryFileSystem {
+            &mut self.file_system
+        }
+
+        #[allow(unused)]
+        pub(crate) fn vfs_mut(&mut self) -> &mut Vfs {
+            &mut self.vfs
+        }
+    }
+
+    impl SourceDb for TestDb {
+        fn file_system(&self) -> &dyn FileSystem {
+            &self.file_system
+        }
+
+        fn vfs(&self) -> &Vfs {
+            &self.vfs
+        }
+    }
+
+    impl Upcast<dyn SourceDb> for TestDb {
+        fn upcast(&self) -> &(dyn SourceDb + 'static) {
+            self
+        }
+    }
+
+    impl Db for TestDb {}
+
+    impl salsa::Database for TestDb {
+        fn salsa_event(&self, event: salsa::Event) {
+            tracing::trace!("event: {:?}", event.debug(self));
+            let mut events = self.events.lock().unwrap();
+            events.push(event);
+        }
+    }
+
+    impl salsa::ParallelDatabase for TestDb {
+        fn snapshot(&self) -> salsa::Snapshot<Self> {
+            salsa::Snapshot::new(Self {
+                storage: self.storage.snapshot(),
+                vfs: self.vfs.snapshot(),
+                file_system: self.file_system.snapshot(),
+                events: self.events.clone(),
+            })
+        }
+    }
+}

crates/ruff_python_semantic/src/lib.rs

@@ -2,6 +2,8 @@ pub mod analyze;
 mod binding;
 mod branches;
 mod context;
+#[cfg(feature = "red_knot")]
+mod db;
 mod definition;
 mod globals;
 mod model;
@@ -20,3 +22,6 @@ pub use nodes::*;
 pub use reference::*;
 pub use scope::*;
 pub use star_import::*;
+
+#[cfg(feature = "red_knot")]
+pub use db::{Db, Jar};