From 5a9d1e5fdde0525a6d0509ad5461224ee476bf22 Mon Sep 17 00:00:00 2001
From: Martin von Zweigbergk <martinvonz@google.com>
Date: Fri, 2 Dec 2022 12:41:25 -0800
Subject: [PATCH] op_store: rename variables in upgrade code to be
 direction-agnostic

The code for migrating from ProtoBuf to Thrift is almost completely
independent of which direction the upgrade goes, so we can very easily
reuse it for migrating from Thrift to Protobuf. This patch renames
some variables to "old/new" instead of "proto/thrift", making the next
patch even simpler.
---
 lib/src/simple_op_store.rs | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/lib/src/simple_op_store.rs b/lib/src/simple_op_store.rs
index e5f85d2f4..5f4304729 100644
--- a/lib/src/simple_op_store.rs
+++ b/lib/src/simple_op_store.rs
@@ -45,7 +45,7 @@ pub struct SimpleOpStore {
 
 fn upgrade_to_thrift(store_path: PathBuf) -> std::io::Result<()> {
     println!("Upgrading operation log to Thrift format...");
-    let proto_store = ProtoOpStore::load(store_path.clone());
+    let old_store = ProtoOpStore::load(store_path.clone());
     let tmp_store_dir = tempfile::Builder::new()
         .prefix("jj-op-store-upgrade-")
         .tempdir_in(store_path.parent().unwrap())
@@ -66,12 +66,12 @@ fn upgrade_to_thrift(store_path: PathBuf) -> std::io::Result<()> {
     }
 
     // Do a DFS to rewrite the operations
-    let thrift_store = ThriftOpStore::init(tmp_store_path.clone());
+    let new_store = ThriftOpStore::init(tmp_store_path.clone());
     let mut converted: HashMap<OperationId, OperationId> = HashMap::new();
     // The DFS stack
     let mut to_convert = old_op_heads
         .iter()
-        .map(|op_id| (op_id.clone(), proto_store.read_operation(op_id).unwrap()))
+        .map(|op_id| (op_id.clone(), old_store.read_operation(op_id).unwrap()))
         .collect_vec();
     while !to_convert.is_empty() {
         let (_, op) = to_convert.last().unwrap();
@@ -83,20 +83,20 @@ fn upgrade_to_thrift(store_path: PathBuf) -> std::io::Result<()> {
             if let Some(new_parent_id) = converted.get(parent_id) {
                 new_parent_ids.push(new_parent_id.clone());
             } else {
-                let parent_op = proto_store.read_operation(parent_id).unwrap();
+                let parent_op = old_store.read_operation(parent_id).unwrap();
                 new_to_convert.push((parent_id.clone(), parent_op));
             }
         }
         if new_to_convert.is_empty() {
             // If all parents have already been converted, remove this operation from the
             // stack and convert it
-            let (op_id, mut op) = to_convert.pop().unwrap();
-            op.parents = new_parent_ids;
-            let view = proto_store.read_view(&op.view_id).unwrap();
-            let thrift_view_id = thrift_store.write_view(&view).unwrap();
-            op.view_id = thrift_view_id;
-            let thrift_op_id = thrift_store.write_operation(&op).unwrap();
-            converted.insert(op_id, thrift_op_id);
+            let (old_op_id, mut old_op) = to_convert.pop().unwrap();
+            old_op.parents = new_parent_ids;
+            let old_view = old_store.read_view(&old_op.view_id).unwrap();
+            let new_view_id = new_store.write_view(&old_view).unwrap();
+            old_op.view_id = new_view_id;
+            let new_op_id = new_store.write_operation(&old_op).unwrap();
+            converted.insert(old_op_id, new_op_id);
         } else {
             to_convert.extend(new_to_convert);
         }