Refactor project state management to use Salsa

crates/djls-conf/src/lib.rs

@@ -21,7 +21,7 @@ pub enum ConfigError {
     PyprojectSerialize(#[from] toml::ser::Error),
 }
 
-#[derive(Debug, Deserialize, Default, PartialEq)]
+#[derive(Debug, Deserialize, Default, PartialEq, Clone)]
 pub struct Settings {
     #[serde(default)]
     debug: bool,

crates/djls-project/src/db.rs

@@ -2,30 +2,33 @@
 //!
 //! This module extends the workspace database trait with project-specific
 //! functionality including metadata access and Python environment discovery.
+//!
+//! ## Architecture
+//!
+//! Following the Salsa pattern established in workspace and templates crates:
+//! - `DjangoProject` is a Salsa input representing external project state
+//! - Tracked functions compute derived values (Python env, Django config)
+//! - Database trait provides stable configuration (metadata, template tags)
+
+use std::path::Path;
+use std::sync::Arc;
 
 use djls_workspace::Db as WorkspaceDb;
 
-use crate::meta::ProjectMetadata;
-use crate::python::PythonEnvironment;
+use crate::inspector::pool::InspectorPool;
+use crate::project::Project;
 
 /// Project-specific database trait extending the workspace database
 #[salsa::db]
 pub trait Db: WorkspaceDb {
-    /// Get the project metadata containing root path and venv configuration
-    fn metadata(&self) -> &ProjectMetadata;
-}
+    /// Get the current project (if set)
+    fn project(&self) -> Option<Project>;
 
-/// Find the Python environment for the project.
-///
-/// This Salsa tracked function discovers the Python environment based on:
-/// 1. Explicit venv path from metadata
-/// 2. VIRTUAL_ENV environment variable
-/// 3. Common venv directories in project root (.venv, venv, env, .env)
-/// 4. System Python as fallback
-#[salsa::tracked]
-pub fn find_python_environment(db: &dyn Db) -> Option<PythonEnvironment> {
-    let project_path = db.metadata().root().as_path();
-    let venv_path = db.metadata().venv().and_then(|p| p.to_str());
+    /// Get the shared inspector pool for executing Python queries
+    fn inspector_pool(&self) -> Arc<InspectorPool>;
 
-    PythonEnvironment::new(project_path, venv_path)
+    /// Get the project root path if a project is set
+    fn project_path(&self) -> Option<&Path> {
+        self.project().map(|p| p.root(self).as_path())
+    }
 }

crates/djls-project/src/django.rs

@@ -0,0 +1,71 @@
+mod templatetags;
+
+pub use templatetags::get_templatetags;
+pub use templatetags::TemplateTags;
+
+use crate::db::Db as ProjectDb;
+use crate::inspector::inspector_run;
+use crate::inspector::queries::Query;
+use crate::python::python_environment;
+use crate::Project;
+
+/// Check if Django is available for the current project.
+///
+/// This determines if Django is installed and configured in the Python environment.
+/// First consults the inspector, then falls back to environment detection.
+#[salsa::tracked]
+pub fn django_available(db: &dyn ProjectDb, project: Project) -> bool {
+    // First try to get Django availability from inspector
+    if let Some(json_data) = inspector_run(db, Query::DjangoInit) {
+        // Parse the JSON response - expect a boolean
+        if let Ok(available) = serde_json::from_str::<bool>(&json_data) {
+            return available;
+        }
+    }
+
+    // Fallback to environment detection
+    python_environment(db, project).is_some()
+}
+
+/// Get the Django settings module name for the current project.
+///
+/// Returns the settings_module_override from project, or inspector result,
+/// or DJANGO_SETTINGS_MODULE env var, or attempts to detect it.
+#[salsa::tracked]
+pub fn django_settings_module(db: &dyn ProjectDb, project: Project) -> Option<String> {
+    // Check project override first
+    if let Some(settings) = project.settings_module(db) {
+        return Some(settings.clone());
+    }
+
+    // Try to get settings module from inspector
+    if let Some(json_data) = inspector_run(db, Query::DjangoInit) {
+        // Parse the JSON response - expect a string
+        if let Ok(settings) = serde_json::from_str::<String>(&json_data) {
+            return Some(settings);
+        }
+    }
+
+    let project_path = project.root(db);
+
+    // Try to detect settings module
+    if project_path.join("manage.py").exists() {
+        // Look for common settings modules
+        for candidate in &["settings", "config.settings", "project.settings"] {
+            let parts: Vec<&str> = candidate.split('.').collect();
+            let mut path = project_path.clone();
+            for part in &parts[..parts.len() - 1] {
+                path = path.join(part);
+            }
+            if let Some(last) = parts.last() {
+                path = path.join(format!("{last}.py"));
+            }
+
+            if path.exists() {
+                return Some((*candidate).to_string());
+            }
+        }
+    }
+
+    None
+}

crates/djls-project/src/templatetags.rs → crates/djls-project/src/django/templatetags.rs

@@ -4,7 +4,30 @@ use anyhow::Context;
 use anyhow::Result;
 use serde_json::Value;
 
-#[derive(Debug, Default, Clone)]
+use crate::db::Db as ProjectDb;
+use crate::inspector::inspector_run;
+use crate::inspector::queries::Query;
+use crate::Project;
+
+/// Get template tags for the current project by querying the inspector.
+///
+/// This tracked function calls the inspector to retrieve Django template tags
+/// and parses the JSON response into a TemplateTags struct.
+#[salsa::tracked]
+pub fn get_templatetags(db: &dyn ProjectDb, _project: Project) -> Option<TemplateTags> {
+    let json_str = inspector_run(db, Query::Templatetags)?;
+
+    // Parse the JSON string into a Value first
+    let json_value: serde_json::Value = match serde_json::from_str(&json_str) {
+        Ok(value) => value,
+        Err(_) => return None,
+    };
+
+    // Parse the JSON data into TemplateTags
+    TemplateTags::from_json(&json_value).ok()
+}
+
+#[derive(Debug, Default, Clone, PartialEq)]
 pub struct TemplateTags(Vec<TemplateTag>);
 
 impl Deref for TemplateTags {
@@ -83,3 +106,29 @@ impl TemplateTag {
         self.doc.as_ref()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_template_tags_parsing() {
+        // Test that TemplateTags can parse valid JSON
+        let json_data = r#"{
+            "templatetags": [
+                {
+                    "name": "test_tag",
+                    "module": "test_module",
+                    "doc": "Test documentation"
+                }
+            ]
+        }"#;
+
+        let value: serde_json::Value = serde_json::from_str(json_data).unwrap();
+        let tags = TemplateTags::from_json(&value).unwrap();
+        assert_eq!(tags.len(), 1);
+        assert_eq!(tags[0].name(), "test_tag");
+        assert_eq!(tags[0].library(), "test_module");
+        assert_eq!(tags[0].doc(), Some(&"Test documentation".to_string()));
+    }
+}

crates/djls-project/src/inspector.rs

@@ -7,6 +7,9 @@ pub use queries::Query;
 use serde::Deserialize;
 use serde::Serialize;
 
+use crate::db::Db as ProjectDb;
+use crate::python::python_environment;
+
 #[derive(Serialize)]
 pub struct DjlsRequest {
     #[serde(flatten)]
@@ -19,3 +22,32 @@ pub struct DjlsResponse {
     pub data: Option<serde_json::Value>,
     pub error: Option<String>,
 }
+
+/// Run an inspector query and return the JSON result as a string.
+///
+/// This tracked function executes inspector queries through the shared pool
+/// and caches the results based on project state and query kind.
+pub fn inspector_run(db: &dyn ProjectDb, query: Query) -> Option<String> {
+    let project = db.project()?;
+    let python_env = python_environment(db, project)?;
+    let project_path = project.root(db);
+
+    match db
+        .inspector_pool()
+        .query(&python_env, project_path, &DjlsRequest { query })
+    {
+        Ok(response) => {
+            if response.ok {
+                if let Some(data) = response.data {
+                    // Convert to JSON string
+                    serde_json::to_string(&data).ok()
+                } else {
+                    None
+                }
+            } else {
+                None
+            }
+        }
+        Err(_) => None,
+    }
+}

crates/djls-project/src/inspector/pool.rs

@@ -11,12 +11,6 @@ use super::DjlsRequest;
 use super::DjlsResponse;
 use crate::python::PythonEnvironment;
 
-/// Global singleton pool for convenience
-static GLOBAL_POOL: std::sync::OnceLock<InspectorPool> = std::sync::OnceLock::new();
-
-pub fn global_pool() -> &'static InspectorPool {
-    GLOBAL_POOL.get_or_init(InspectorPool::new)
-}
 const DEFAULT_IDLE_TIMEOUT: Duration = Duration::from_secs(60);
 
 /// Manages a pool of inspector processes with automatic cleanup

crates/djls-project/src/inspector/queries.rs

@@ -3,16 +3,17 @@ use std::path::PathBuf;
 use serde::Deserialize;
 use serde::Serialize;
 
-#[derive(Serialize, Deserialize)]
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, Hash, Copy)]
 #[serde(tag = "query", content = "args")]
 #[serde(rename_all = "snake_case")]
 pub enum Query {
+    DjangoInit,
     PythonEnv,
     Templatetags,
-    DjangoInit,
 }
 
 #[derive(Serialize, Deserialize)]
+#[allow(clippy::struct_field_names)]
 pub struct PythonEnvironmentQueryData {
     pub sys_base_prefix: PathBuf,
     pub sys_executable: PathBuf,
@@ -42,3 +43,21 @@ pub struct TemplateTag {
     pub module: String,
     pub doc: Option<String>,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_query_enum() {
+        // Test that Query variants exist and are copyable
+        let python_env = Query::PythonEnv;
+        let templatetags = Query::Templatetags;
+        let django_init = Query::DjangoInit;
+
+        // Test that they can be copied
+        assert_eq!(python_env, Query::PythonEnv);
+        assert_eq!(templatetags, Query::Templatetags);
+        assert_eq!(django_init, Query::DjangoInit);
+    }
+}