feat(node): complete implementation of v3 → v4 chain state migration

node/src/storage_mngr/node_migrations.rs

@@ -62,21 +62,27 @@ fn migrate_chain_state_v3_to_v4(old_chain_state_bytes: &[u8]) -> Vec<u8> {
     let db_version: u32 = 4;
     let db_version_bytes = db_version.to_le_bytes();
 
-    // FIXME: the protocol info migration is not 100% correct, for reasons unknown.
-    // Extra fields in ChainState v4:
-    let protocol_info = ProtocolInfo::default();
-    let protocol_info_bytes = serialize(&protocol_info).unwrap();
-    let stakes = StakesTracker::default();
-    let stakes_bytes = serialize(&stakes).unwrap();
-
-    [
-        &db_version_bytes,
-        &old_chain_state_bytes[4..5],
-        &protocol_info_bytes,
-        &old_chain_state_bytes[5..],
-        &stakes_bytes,
-    ]
-    .concat()
+    // This little trick makes sure that we don't run a migration on a v4 chain state that was
+    // incorrectly tagged as v3 in the context of a development release, by checking if the bytes
+    // match a pattern where the environment enum is stored at a certain position
+    if old_chain_state_bytes[5..9] == [0x02, 0x00, 0x00, 0x00] {
+        // Extra fields in ChainState v4:
+        let protocol_info = ProtocolInfo::default();
+        let protocol_info_bytes = serialize(&protocol_info).unwrap();
+        let stakes = StakesTracker::default();
+        let stakes_bytes = serialize(&stakes).unwrap();
+
+        [
+            &db_version_bytes,
+            &old_chain_state_bytes[4..5],
+            &protocol_info_bytes,
+            &old_chain_state_bytes[5..],
+            &stakes_bytes,
+        ]
+        .concat()
+    } else {
+        [&db_version_bytes, &old_chain_state_bytes[4..]].concat()
+    }
 }
 
 fn migrate_chain_state(mut bytes: Vec<u8>) -> Result<ChainState, failure::Error> {
@@ -208,7 +214,7 @@ pub fn put_chain_state_in_batch<K>(
 where
     K: serde::Serialize + 'static,
 {
-    let db_version: u32 = 3;
+    let db_version: u32 = 4;
     // The first byte of the ChainState db_version must never be 0 or 1,
     // because that can be confused with version 0.
     assert!(db_version.to_le_bytes()[0] >= 2);