index: add 'static version of evaluate_revset() to ReadonlyIndex

We'll probably need a better abstraction, but a separate method is good
enough to remove unsafe code from ReadonlyRepo.

I'm not sure if this is feasible for the other backends, but I guess there
would be less lifetimed variables than DefaultReadonlyIndex.

lib/src/default_index/readonly.rs

@@ -30,6 +30,7 @@ use super::entry::{IndexEntry, IndexPosition, SmallIndexPositionsVec};
 use super::mutable::DefaultMutableIndex;
 use super::store::IndexLoadError;
 use crate::backend::{ChangeId, CommitId, ObjectId};
+use crate::default_revset_engine;
 use crate::index::{HexPrefix, Index, MutableIndex, PrefixResolution, ReadonlyIndex};
 use crate::revset::{ResolvedExpression, Revset, RevsetEvaluationError};
 use crate::store::Store;
@@ -373,7 +374,7 @@ impl IndexSegment for ReadonlyIndexSegment {
 }
 
 /// Commit index backend which stores data on local disk.
-#[derive(Debug)]
+#[derive(Clone, Debug)]
 pub struct DefaultReadonlyIndex(Arc<ReadonlyIndexSegment>);
 
 impl DefaultReadonlyIndex {
@@ -440,6 +441,15 @@ impl ReadonlyIndex for DefaultReadonlyIndex {
         self
     }
 
+    fn evaluate_revset_static(
+        &self,
+        expression: &ResolvedExpression,
+        store: &Arc<Store>,
+    ) -> Result<Box<dyn Revset<'static>>, RevsetEvaluationError> {
+        let revset_impl = default_revset_engine::evaluate(expression, store, self.clone())?;
+        Ok(Box::new(revset_impl))
+    }
+
     fn start_modification(&self) -> Box<dyn MutableIndex> {
         Box::new(DefaultMutableIndex::incremental(self.0.clone()))
     }

lib/src/index.rs

@@ -75,6 +75,14 @@ pub trait ReadonlyIndex: Send + Sync {
 
     fn as_index(&self) -> &dyn Index;
 
+    // TODO: might be better to split Index::evaluate_revset() to
+    // Readonly/MutableIndex::evaluate_static().
+    fn evaluate_revset_static(
+        &self,
+        expression: &ResolvedExpression,
+        store: &Arc<Store>,
+    ) -> Result<Box<dyn Revset<'static>>, RevsetEvaluationError>;
+
     fn start_modification(&self) -> Box<dyn MutableIndex>;
 }
 

lib/tests/test_default_revset_graph_iterator.rs

@@ -22,10 +22,10 @@ use jj_lib::revset_graph::RevsetGraphEdge;
 use test_case::test_case;
 use testutils::{CommitGraphBuilder, TestRepo};
 
-fn revset_for_commits<'index>(
+fn revset_for_commits(
-    repo: &'index ReadonlyRepo,
+    repo: &ReadonlyRepo,
     commits: &[&Commit],
-) -> RevsetImpl<&'index DefaultReadonlyIndex> {
+) -> RevsetImpl<DefaultReadonlyIndex> {
     let index = repo
         .readonly_index()
         .as_any()
@@ -33,7 +33,7 @@ fn revset_for_commits<'index>(
         .unwrap();
     let expression =
         ResolvedExpression::Commits(commits.iter().map(|commit| commit.id().clone()).collect());
-    evaluate(&expression, repo.store(), index).unwrap()
+    evaluate(&expression, repo.store(), index.clone()).unwrap()
 }
 
 fn direct(commit: &Commit) -> RevsetGraphEdge {