Impl Analysis interface

src/base.rs

@@ -55,7 +55,7 @@ impl Change {
         self.file_changes.push((file_id, content));
     }
 
-    pub fn apply(self, db: &mut dyn SourceDatabase) {
+    pub(crate) fn apply(self, db: &mut dyn SourceDatabase) {
         for (file_id, content) in self.file_changes {
             let content = content.unwrap_or_else(|| String::new().into());
             // TODO: Better guess of durability?

src/ide/mod.rs

@@ -1,6 +1,6 @@
-use crate::FileId;
-use crate::{base::SourceDatabaseStorage, def::DefDatabaseStorage};
+use crate::{base::SourceDatabaseStorage, def::DefDatabaseStorage, Change, FileId, FilePos};
 use rowan::TextRange;
+use salsa::{Cancelled, Database, Durability, ParallelDatabase};
 use std::fmt;
 
 mod goto_definition;
@@ -12,6 +12,8 @@ pub struct NavigationTarget {
     pub focus_range: TextRange,
 }
 
+pub type Cancellable<T> = Result<T, Cancelled>;
+
 #[salsa::database(SourceDatabaseStorage, DefDatabaseStorage)]
 #[derive(Default)]
 pub struct RootDatabase {
@@ -33,3 +35,47 @@ impl fmt::Debug for RootDatabase {
         f.debug_struct("RootDatabase").finish_non_exhaustive()
     }
 }
+
+#[derive(Debug, Default)]
+pub struct AnalysisHost {
+    db: RootDatabase,
+}
+
+impl AnalysisHost {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    pub fn snapshot(&self) -> Analysis {
+        Analysis {
+            db: self.db.snapshot(),
+        }
+    }
+
+    pub fn request_cancellation(&mut self) {
+        self.db.salsa_runtime_mut().synthetic_write(Durability::LOW);
+    }
+
+    pub fn apply_change(&mut self, change: Change) {
+        self.request_cancellation();
+        change.apply(&mut self.db);
+    }
+}
+
+#[derive(Debug)]
+pub struct Analysis {
+    db: salsa::Snapshot<RootDatabase>,
+}
+
+impl Analysis {
+    fn with_db<F, T>(&self, f: F) -> Cancellable<T>
+    where
+        F: FnOnce(&RootDatabase) -> T + std::panic::UnwindSafe,
+    {
+        Cancelled::catch(|| f(&self.db))
+    }
+
+    pub fn goto_definition(&self, pos: FilePos) -> Cancellable<Option<NavigationTarget>> {
+        self.with_db(|db| goto_definition::goto_definition(db, pos.file_id, pos.value))
+    }
+}

src/lib.rs

@@ -6,4 +6,4 @@ mod ide;
 mod tests;
 
 pub use base::{Change, FileId, FilePos, InFile};
-pub use ide::RootDatabase;
+pub use ide::{Analysis, AnalysisHost, RootDatabase};