fix(sns-wasm): actually overwrite existing SNS-specific upgrade path entries

rs/nns/sns-wasm/src/sns_wasm.rs

@@ -1940,14 +1940,15 @@ impl UpgradePath {
             .or_default()
             .entry(from)
         {
-            Entry::Occupied(occupied) => {
+            Entry::Occupied(mut occupied) => {
                 println!(
                     "Special Entry for {}  from {:?} to {:?} is being overwritten with new value {:?}",
                     sns_governance_canister_id,
                     occupied.key(),
                     occupied.get(),
                     to
                 );
+                occupied.insert(to);
             }
             Entry::Vacant(vacant) => {
                 vacant.insert(to);
@@ -5646,4 +5647,45 @@ mod test {
             );
         }
     }
+
+    #[test]
+    fn test_insert_sns_specific_upgrade_path_entry_overwrites_existing_entry() {
+        let sns_governance_canister_id = CanisterId::from_u64(1000);
+        let from_version = SnsVersion {
+            governance_wasm_hash: vec![1],
+            ..Default::default()
+        };
+        let first_to_version = SnsVersion {
+            governance_wasm_hash: vec![2],
+            ..Default::default()
+        };
+        let second_to_version = SnsVersion {
+            governance_wasm_hash: vec![3],
+            ..Default::default()
+        };
+
+        let mut upgrade_path = UpgradePath::default();
+        upgrade_path.insert_sns_specific_upgrade_path_entry(
+            from_version.clone(),
+            first_to_version.clone(),
+            sns_governance_canister_id,
+        );
+        assert_eq!(
+            upgrade_path.get_next_version(from_version.clone(), sns_governance_canister_id.get()),
+            Some(first_to_version)
+        );
+
+        // Run code under test: reconfigure the same `from_version` entry with a new target.
+        upgrade_path.insert_sns_specific_upgrade_path_entry(
+            from_version.clone(),
+            second_to_version.clone(),
+            sns_governance_canister_id,
+        );
+
+        // The entry must reflect the new target, not the stale first one.
+        assert_eq!(
+            upgrade_path.get_next_version(from_version, sns_governance_canister_id.get()),
+            Some(second_to_version)
+        );
+    }
 }

rs/nns/sns-wasm/unreleased_changelog.md

@@ -17,4 +17,9 @@ on the process that this file is part of, see
 
 ## Fixed
 
+* `insert_sns_specific_upgrade_path_entry` now actually replaces an
+  SNS-specific emergency upgrade step when called again for the same SNS
+  and starting version, instead of silently keeping the old step while
+  reporting success.
+
 ## Security