From acdcb578bc5079b2adefd8a9afdf2d43723b4b44 Mon Sep 17 00:00:00 2001
From: Martin von Zweigbergk <martinvonz@google.com>
Date: Thu, 22 Aug 2024 21:37:59 -0700
Subject: [PATCH] copies: in unsupported backends, return an empty stream
 instead of error

The native backend currently errors out if you ask it about copies. So
does the test backend. I think it's better to return an empty stream
of copies so it doesn't prevent other functionality.
---
 lib/src/local_backend.rs          | 3 ++-
 lib/testutils/src/test_backend.rs | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/src/local_backend.rs b/lib/src/local_backend.rs
index 05164e46e..f541f8e3e 100644
--- a/lib/src/local_backend.rs
+++ b/lib/src/local_backend.rs
@@ -27,6 +27,7 @@ use std::time::SystemTime;
 use async_trait::async_trait;
 use blake2::Blake2b512;
 use blake2::Digest;
+use futures::stream;
 use futures::stream::BoxStream;
 use prost::Message;
 use tempfile::NamedTempFile;
@@ -330,7 +331,7 @@ impl Backend for LocalBackend {
         _root: &CommitId,
         _head: &CommitId,
     ) -> BackendResult<BoxStream<BackendResult<CopyRecord>>> {
-        Err(BackendError::Unsupported("get_copy_records".into()))
+        Ok(Box::pin(stream::empty()))
     }
 
     fn gc(&self, _index: &dyn Index, _keep_newer: SystemTime) -> BackendResult<()> {
diff --git a/lib/testutils/src/test_backend.rs b/lib/testutils/src/test_backend.rs
index 6fc7c49ab..b0282471e 100644
--- a/lib/testutils/src/test_backend.rs
+++ b/lib/testutils/src/test_backend.rs
@@ -28,6 +28,7 @@ use std::sync::OnceLock;
 use std::time::SystemTime;
 
 use async_trait::async_trait;
+use futures::stream;
 use futures::stream::BoxStream;
 use jj_lib::backend::make_root_commit;
 use jj_lib::backend::Backend;
@@ -327,7 +328,7 @@ impl Backend for TestBackend {
         _root: &CommitId,
         _head: &CommitId,
     ) -> BackendResult<BoxStream<BackendResult<CopyRecord>>> {
-        Err(BackendError::Unsupported("get_copy_records".into()))
+        Ok(Box::pin(stream::empty()))
     }
 
     fn gc(&self, _index: &dyn Index, _keep_newer: SystemTime) -> BackendResult<()> {