Fix epoched last update

.changelog/unreleased/bug-fixes/2667-fix-last-update-usage.md

@@ -0,0 +1,2 @@
+- Fix the setting of the last update field in an Epoched data structure.
+  ([\#2667](https://github.com/anoma/namada/pull/2667))

crates/proof_of_stake/src/epoched.rs

@@ -444,13 +444,11 @@ where
                 //     panic!("WARNING: no data existing in
                 // {new_oldest_epoch}"); }
                 self.set_oldest_epoch(storage, new_oldest_epoch)?;
-
-                // Update the epoch of the last update to the current epoch
-                let key = self.get_last_update_storage_key();
-                storage.write(&key, current_epoch)?;
-                return Ok(());
             }
         }
+        // Update the epoch of the last update to the current epoch
+        let key = self.get_last_update_storage_key();
+        storage.write(&key, current_epoch)?;
 
         Ok(())
     }

crates/proof_of_stake/src/lib.rs

@@ -2205,7 +2205,8 @@
             // Promote the next below-capacity validator to consensus
             promote_next_below_capacity_validator_to_consensus(
                 storage,
-                pipeline_epoch,
+                current_epoch,
+                params.pipeline_len,
             )?;
         }
 
@@ -2290,8 +2291,8 @@
             validator_state_handle(validator).set(
                 storage,
                 ValidatorState::Jailed,
-                pipeline_epoch,
-                0,
+                current_epoch,
+                params.pipeline_len,
             )?;
             return Ok(());
         }
@@ -2698,10 +2699,14 @@
 
     // Remove the validator from the set starting at the update epoch and up
     // thru the pipeline epoch.
-    let pipeline_epoch = current_epoch + params.pipeline_len;
-    for epoch in
-        Epoch::iter_bounds_inclusive(validator_set_update_epoch, pipeline_epoch)
-    {
+    let start = validator_set_update_epoch
+        .0
+        .checked_sub(current_epoch.0)
+        .unwrap(); // Safe unwrap
+    let end = params.pipeline_len;
+
+    for offset in start..=end {
+        let epoch = current_epoch + offset;
         let prev_state = validator_state_handle(validator)
             .get(storage, epoch, params)?
             .expect("Expected to find a valid validator.");
@@ -2716,9 +2721,11 @@
                 // For the pipeline epoch only:
                 // promote the next max inactive validator to the active
                 // validator set at the pipeline offset
-                if epoch == pipeline_epoch {
+                if offset == params.pipeline_len {
                     promote_next_below_capacity_validator_to_consensus(
-                        storage, epoch,
+                        storage,
+                        current_epoch,
+                        offset,
                     )?;
                 }
             }

crates/proof_of_stake/src/tests/test_validator.rs

@@ -1320,8 +1320,20 @@ fn test_purge_validator_information_aux(validators: Vec<GenesisValidator>) {
 
     // Check that there is validator data for epochs 0 - pipeline_len
     check_is_data(&s, current_epoch, Epoch(params.owned.pipeline_len));
+    assert_eq!(
+        consensus_val_set.get_last_update(&s).unwrap().unwrap(),
+        Epoch(0)
+    );
+    assert_eq!(
+        validator_positions.get_last_update(&s).unwrap().unwrap(),
+        Epoch(0)
+    );
+    assert_eq!(
+        validator_positions.get_last_update(&s).unwrap().unwrap(),
+        Epoch(0)
+    );
 
-    // Advance to epoch 1
+    // Advance to epoch `default_past_epochs`
     for _ in 0..default_past_epochs {
         current_epoch = advance_epoch(&mut s, &params);
     }
@@ -1333,6 +1345,18 @@ fn test_purge_validator_information_aux(validators: Vec<GenesisValidator>) {
         Epoch(0),
         Epoch(params.owned.pipeline_len + default_past_epochs),
     );
+    assert_eq!(
+        consensus_val_set.get_last_update(&s).unwrap().unwrap(),
+        Epoch(default_past_epochs)
+    );
+    assert_eq!(
+        validator_positions.get_last_update(&s).unwrap().unwrap(),
+        Epoch(default_past_epochs)
+    );
+    assert_eq!(
+        validator_positions.get_last_update(&s).unwrap().unwrap(),
+        Epoch(default_past_epochs)
+    );
 
     current_epoch = advance_epoch(&mut s, &params);
     assert_eq!(current_epoch.0, default_past_epochs + 1);

crates/proof_of_stake/src/validator_set_update.rs

@@ -521,11 +521,13 @@ where
 /// consensus set already.
 pub fn promote_next_below_capacity_validator_to_consensus<S>(
     storage: &mut S,
-    epoch: Epoch,
+    current_epoch: Epoch,
+    offset: u64,
 ) -> namada_storage::Result<()>
 where
     S: StorageRead + StorageWrite,
 {
+    let epoch = current_epoch + offset;
     let below_cap_set = below_capacity_validator_set_handle().at(&epoch);
     let max_below_capacity_amount =
         get_max_below_capacity_validator_amount(&below_cap_set, storage)?;
@@ -550,8 +552,8 @@ where
         validator_state_handle(&promoted_validator).set(
             storage,
             ValidatorState::Consensus,
-            epoch,
-            0,
+            current_epoch,
+            offset,
         )?;
     }
 
@@ -828,6 +830,7 @@ where
             .at(&val_stake)
             .insert(storage, val_position, val_address)?;
     }
+
     // Purge consensus and below-capacity validator sets
     consensus_validator_set.update_data(storage, params, current_epoch)?;
     below_capacity_validator_set.update_data(storage, params, current_epoch)?;
@@ -847,7 +850,6 @@ where
         let prev = new_positions_handle.insert(storage, validator, position)?;
         debug_assert!(prev.is_none());
     }
-    validator_set_positions_handle.set_last_update(storage, current_epoch)?;
 
     // Purge old epochs of validator positions
     validator_set_positions_handle.update_data(