From 61e4bd4e85a8a395901f66ef7eb0c2bb062f0b63 Mon Sep 17 00:00:00 2001
From: Yuya Nishihara <yuya@tcha.org>
Date: Thu, 8 Aug 2024 23:42:47 +0900
Subject: [PATCH] tree: fill in valid id to null tree, rename function to
 empty()

If a null tree were written to the store, GitBackend would crash because of
invalid hash length.
---
 lib/src/local_working_copy.rs | 2 +-
 lib/src/merge.rs              | 2 +-
 lib/src/merged_tree.rs        | 8 ++++----
 lib/src/tree.rs               | 5 +++--
 lib/src/tree_builder.rs       | 2 +-
 5 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/lib/src/local_working_copy.rs b/lib/src/local_working_copy.rs
index 7a52af951dc..0b3ea2a60c8 100644
--- a/lib/src/local_working_copy.rs
+++ b/lib/src/local_working_copy.rs
@@ -1315,7 +1315,7 @@ impl TreeState {
         let new_matcher = PrefixMatcher::new(&sparse_patterns);
         let added_matcher = DifferenceMatcher::new(&new_matcher, &old_matcher);
         let removed_matcher = DifferenceMatcher::new(&old_matcher, &new_matcher);
-        let empty_tree = MergedTree::resolved(Tree::null(self.store.clone(), RepoPathBuf::root()));
+        let empty_tree = MergedTree::resolved(Tree::empty(self.store.clone(), RepoPathBuf::root()));
         let added_stats = self.update(&empty_tree, &tree, &added_matcher).block_on()?;
         let removed_stats = self
             .update(&tree, &empty_tree, &removed_matcher)
diff --git a/lib/src/merge.rs b/lib/src/merge.rs
index e16786ee36c..6569f842a7f 100644
--- a/lib/src/merge.rs
+++ b/lib/src/merge.rs
@@ -625,7 +625,7 @@ where
                 if let Some(id) = id {
                     store.get_tree(dir, id)
                 } else {
-                    Ok(Tree::null(store.clone(), dir.to_owned()))
+                    Ok(Tree::empty(store.clone(), dir.to_owned()))
                 }
             };
             Ok(Some(tree_id_merge.try_map(get_tree)?))
diff --git a/lib/src/merged_tree.rs b/lib/src/merged_tree.rs
index 621465495d6..f83acf77ad9 100644
--- a/lib/src/merged_tree.rs
+++ b/lib/src/merged_tree.rs
@@ -209,7 +209,7 @@ impl MergedTree {
                     }
                     _ => {
                         let subdir = self.dir().join(name);
-                        Ok(Tree::null(self.store().clone(), subdir.clone()))
+                        Ok(Tree::empty(self.store().clone(), subdir.clone()))
                     }
                 })?;
                 Ok(Some(MergedTree { trees }))
@@ -642,7 +642,7 @@ impl<'matcher> TreeDiffIterator<'matcher> {
         if let Some(trees) = values.to_tree_merge(store, dir)? {
             Ok(trees)
         } else {
-            Ok(Merge::resolved(Tree::null(store.clone(), dir.to_owned())))
+            Ok(Merge::resolved(Tree::empty(store.clone(), dir.to_owned())))
         }
     }
 }
@@ -846,7 +846,7 @@ impl<'matcher> TreeDiffStreamImpl<'matcher> {
     ) -> BackendResult<Tree> {
         match value {
             Some(TreeValue::Tree(tree_id)) => store.get_tree_async(dir, tree_id).await,
-            _ => Ok(Tree::null(store.clone(), dir.to_owned())),
+            _ => Ok(Tree::empty(store.clone(), dir.to_owned())),
         }
     }
 
@@ -863,7 +863,7 @@ impl<'matcher> TreeDiffStreamImpl<'matcher> {
                 .await?;
             builder.build()
         } else {
-            Merge::resolved(Tree::null(store, dir.clone()))
+            Merge::resolved(Tree::empty(store, dir.clone()))
         };
         Ok(MergedTree { trees })
     }
diff --git a/lib/src/tree.rs b/lib/src/tree.rs
index 2d4a4d86b0c..75066144ca4 100644
--- a/lib/src/tree.rs
+++ b/lib/src/tree.rs
@@ -76,11 +76,12 @@ impl Tree {
         }
     }
 
-    pub fn null(store: Arc<Store>, dir: RepoPathBuf) -> Self {
+    pub fn empty(store: Arc<Store>, dir: RepoPathBuf) -> Self {
+        let id = store.empty_tree_id().clone();
         Tree {
             store,
             dir,
-            id: TreeId::new(vec![]),
+            id,
             data: Arc::new(backend::Tree::default()),
         }
     }
diff --git a/lib/src/tree_builder.rs b/lib/src/tree_builder.rs
index 88fc0d33516..0b3bf4457ea 100644
--- a/lib/src/tree_builder.rs
+++ b/lib/src/tree_builder.rs
@@ -136,7 +136,7 @@ impl TreeBuilder {
             let (parent, basename) = dir.split().expect("root must be populated");
             let tree = populate_trees(tree_cache, store, parent)?
                 .sub_tree(basename)?
-                .unwrap_or_else(|| Tree::null(store.clone(), dir.to_owned()));
+                .unwrap_or_else(|| Tree::empty(store.clone(), dir.to_owned()));
             Ok(tree_cache.entry(dir.to_owned()).or_insert(tree))
         }