introduce salsa and integrate into djls-project crate (#139)

Author: joshuadavidthomas

CHANGELOG.md

@@ -30,6 +30,7 @@ and this project attempts to adhere to [Semantic Versioning](https://semver.org/
 - **Internal**: Moved task queueing functionality to `djls-server` crate, renamed from `Worker` to `Queue`, and simplified API.
 - **Internal**: Improved Python environment handling, including refactored activation logic.
 - **Internal**: Centralized Python linking build logic into a shared `djls-dev` crate to reduce duplication.
+- **Internal (djls-project)**: Started Salsa integration for incremental computation with database structure and initial Python environment discovery functionality.
 
 ## [5.2.0a0]
 

Cargo.toml

@@ -15,6 +15,7 @@ async-trait = "0.1"
 pyo3 = "0.24"
 pyo3-async-runtimes = "0.24"
 pyo3-build-config = "0.24"
+salsa = { git = "https://github.com/salsa-rs/salsa.git", rev = "7edce6e248f35c8114b4b021cdb474a3fb2813b3" }
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 tempfile = "3.19"

crates/djls-project/Cargo.toml

@@ -9,6 +9,7 @@ default = []
 
 [dependencies]
 pyo3 = { workspace = true }
+salsa = { workspace = true }
 tower-lsp-server = { workspace = true, features = ["proposed"] }
 
 which = "7.0.1"

crates/djls-project/src/db.rs

@@ -0,0 +1,31 @@
+use crate::meta::ProjectMetadata;
+
+#[salsa::db]
+pub trait Db: salsa::Database {
+    fn metadata(&self) -> &ProjectMetadata;
+}
+
+#[salsa::db]
+#[derive(Clone)]
+pub struct ProjectDatabase {
+    storage: salsa::Storage<ProjectDatabase>,
+    metadata: ProjectMetadata,
+}
+
+impl ProjectDatabase {
+    pub fn new(metadata: ProjectMetadata) -> Self {
+        let storage = salsa::Storage::new(None);
+
+        Self { storage, metadata }
+    }
+}
+
+#[salsa::db]
+impl Db for ProjectDatabase {
+    fn metadata(&self) -> &ProjectMetadata {
+        &self.metadata
+    }
+}
+
+#[salsa::db]
+impl salsa::Database for ProjectDatabase {}