Prepare SourceDatabase API for lazy file loading

crates/ra_db/src/lib.rs

@@ -64,21 +64,39 @@ pub struct FileRange {
 
 pub const DEFAULT_LRU_CAP: usize = 128;
 
+pub trait FileLoader {
+    /// Text of the file.
+    fn file_text(&self, file_id: FileId) -> Arc<String>;
+    fn resolve_relative_path(&self, anchor: FileId, relative_path: &RelativePath)
+        -> Option<FileId>;
+    fn relevant_crates(&self, file_id: FileId) -> Arc<Vec<CrateId>>;
+}
+
 /// Database which stores all significant input facts: source code and project
 /// model. Everything else in rust-analyzer is derived from these queries.
 #[salsa::query_group(SourceDatabaseStorage)]
-pub trait SourceDatabase: CheckCanceled + std::fmt::Debug {
-    /// Text of the file.
-    #[salsa::input]
-    fn file_text(&self, file_id: FileId) -> Arc<String>;
-
-    #[salsa::transparent]
-    fn resolve_relative_path(&self, anchor: FileId, relative_path: &RelativePath)
-        -> Option<FileId>;
-
+pub trait SourceDatabase: CheckCanceled + FileLoader + std::fmt::Debug {
     // Parses the file into the syntax tree.
     #[salsa::invoke(parse_query)]
     fn parse(&self, file_id: FileId) -> Parse<ast::SourceFile>;
+
+    /// The crate graph.
+    #[salsa::input]
+    fn crate_graph(&self) -> Arc<CrateGraph>;
+}
+
+fn parse_query(db: &impl SourceDatabase, file_id: FileId) -> Parse<ast::SourceFile> {
+    let _p = profile("parse_query");
+    let text = db.file_text(file_id);
+    SourceFile::parse(&*text)
+}
+
+/// We don't want to give HIR knowledge of source roots, hence we extract these
+/// methods into a separate DB.
+#[salsa::query_group(SourceDatabaseExtStorage)]
+pub trait SourceDatabaseExt: SourceDatabase {
+    #[salsa::input]
+    fn file_text(&self, file_id: FileId) -> Arc<String>;
     /// Path to a file, relative to the root of its source root.
     #[salsa::input]
     fn file_relative_path(&self, file_id: FileId) -> RelativePathBuf;
@@ -88,40 +106,48 @@ pub trait SourceDatabase: CheckCanceled + std::fmt::Debug {
     /// Contents of the source root.
     #[salsa::input]
     fn source_root(&self, id: SourceRootId) -> Arc<SourceRoot>;
+
     fn source_root_crates(&self, id: SourceRootId) -> Arc<Vec<CrateId>>;
-    /// The crate graph.
-    #[salsa::input]
-    fn crate_graph(&self) -> Arc<CrateGraph>;
 }
 
-fn resolve_relative_path(
-    db: &impl SourceDatabase,
-    anchor: FileId,
-    relative_path: &RelativePath,
-) -> Option<FileId> {
-    let path = {
-        let mut path = db.file_relative_path(anchor);
-        // Workaround for relative path API: turn `lib.rs` into ``.
-        if !path.pop() {
-            path = RelativePathBuf::default();
-        }
-        path.push(relative_path);
-        path.normalize()
-    };
-    let source_root = db.file_source_root(anchor);
-    let source_root = db.source_root(source_root);
-    source_root.file_by_relative_path(&path)
-}
-
-fn source_root_crates(db: &impl SourceDatabase, id: SourceRootId) -> Arc<Vec<CrateId>> {
+fn source_root_crates(
+    db: &(impl SourceDatabaseExt + SourceDatabase),
+    id: SourceRootId,
+) -> Arc<Vec<CrateId>> {
     let root = db.source_root(id);
     let graph = db.crate_graph();
     let res = root.walk().filter_map(|it| graph.crate_id_for_crate_root(it)).collect::<Vec<_>>();
     Arc::new(res)
 }
 
-fn parse_query(db: &impl SourceDatabase, file_id: FileId) -> Parse<ast::SourceFile> {
-    let _p = profile("parse_query");
-    let text = db.file_text(file_id);
-    SourceFile::parse(&*text)
+/// Silly workaround for cyclic deps between the traits
+pub struct FileLoaderDelegate<T>(pub T);
+
+impl<T: SourceDatabaseExt> FileLoader for FileLoaderDelegate<&'_ T> {
+    fn file_text(&self, file_id: FileId) -> Arc<String> {
+        SourceDatabaseExt::file_text(self.0, file_id)
+    }
+    fn resolve_relative_path(
+        &self,
+        anchor: FileId,
+        relative_path: &RelativePath,
+    ) -> Option<FileId> {
+        let path = {
+            let mut path = self.0.file_relative_path(anchor);
+            // Workaround for relative path API: turn `lib.rs` into ``.
+            if !path.pop() {
+                path = RelativePathBuf::default();
+            }
+            path.push(relative_path);
+            path.normalize()
+        };
+        let source_root = self.0.file_source_root(anchor);
+        let source_root = self.0.source_root(source_root);
+        source_root.file_by_relative_path(&path)
+    }
+
+    fn relevant_crates(&self, file_id: FileId) -> Arc<Vec<CrateId>> {
+        let source_root = self.0.file_source_root(file_id);
+        self.0.source_root_crates(source_root)
+    }
 }