fix: Do not send slashing vote if computed vote is zero

Fixes https://linear.app/aztec-labs/issue/TMNT-231/inconsistent-voting-empty-votes

Author: spalladino

yarn-project/slasher/src/empire_slasher_client.test.ts

@@ -48,6 +48,7 @@ describe('EmpireSlasherClient', () => {
     l1StartBlock: 0n,
     slotDuration: 4,
     ethereumSlotDuration: 12,
+    slashingAmounts: undefined,
   };
 
   const config: SlasherConfig = {

yarn-project/slasher/src/factory/create_implementation.ts

@@ -93,6 +93,7 @@ async function createEmpireSlasher(
     slotDuration: Number(slotDuration),
     l1StartBlock,
     ethereumSlotDuration: config.ethereumSlotDuration,
+    slashingAmounts: undefined,
   };
 
   const payloadsStore = new SlasherPayloadsStore(kvStore, {

yarn-project/slasher/src/slash_offenses_collector.test.ts

@@ -21,6 +21,7 @@ describe('SlashOffensesCollector', () => {
 
   const settings: SlashOffensesCollectorSettings = {
     epochDuration: 32,
+    slashingAmounts: [100n, 200n, 300n],
   };
 
   const config: SlasherConfig = {

yarn-project/slasher/src/slash_offenses_collector.ts

@@ -8,7 +8,9 @@ import type { SlasherOffensesStore } from './stores/offenses_store.js';
 import { WANT_TO_SLASH_EVENT, type WantToSlashArgs, type Watcher } from './watcher.js';
 
 export type SlashOffensesCollectorConfig = Prettify<Pick<SlasherConfig, 'slashGracePeriodL2Slots'>>;
-export type SlashOffensesCollectorSettings = Prettify<Pick<L1RollupConstants, 'epochDuration'>>;
+export type SlashOffensesCollectorSettings = Prettify<
+  Pick<L1RollupConstants, 'epochDuration'> & { slashingAmounts: [bigint, bigint, bigint] | undefined }
+>;
 
 /**
  * Collects and manages slashable offenses from watchers.
@@ -76,6 +78,13 @@ export class SlashOffensesCollector {
         continue;
       }
 
+      if (this.settings.slashingAmounts) {
+        const minSlash = this.settings.slashingAmounts[0];
+        if (arg.amount < minSlash) {
+          this.log.warn(`Offense amount ${arg.amount} is below minimum slashing amount ${minSlash}`);
+        }
+      }
+
       this.log.info(`Adding pending offense for validator ${arg.validator}`, pendingOffense);
       await this.offensesStore.addPendingOffense(pendingOffense);
     }

yarn-project/slasher/src/tally_slasher_client.test.ts

@@ -271,6 +271,26 @@ describe('TallySlasherClient', () => {
         expect(action.committees[0]).toHaveLength(settings.targetCommitteeSize);
         expect(action.committees[0][0].toString()).toEqual(EthAddress.ZERO.toString());
       });
+
+      it('should not return any action when computed votes are zero', async () => {
+        // Round 5 votes on round 3 (offset of 2)
+        const currentRound = 5n;
+        const currentSlot = currentRound * BigInt(roundSize);
+        const targetRound = 3n;
+
+        // Add slot-based offense for the target round
+        await offensesStore.addPendingOffense(
+          createOffense({
+            validator: committee[0],
+            epochOrSlot: targetRound * BigInt(roundSize),
+            offenseType: OffenseType.PROPOSED_INSUFFICIENT_ATTESTATIONS, // slot-based
+            amount: 1n, // Too low to reach minimum slash unit
+          }),
+        );
+
+        const actions = await tallySlasherClient.getProposerActions(currentSlot);
+        expect(actions).toHaveLength(0);
+      });
     });
 
     describe('execute-slash', () => {
@@ -574,7 +594,7 @@ describe('TallySlasherClient', () => {
     it('should handle from offense detection to execution', async () => {
       // Round 3: Offense occurs
       const offenseRound = 3n;
-      const validator = EthAddress.random();
+      const validator = committee[0];
       const offense: WantToSlashArgs = {
         validator,
         amount: settings.slashingAmounts[1],

yarn-project/slasher/src/tally_slasher_client.ts

@@ -292,6 +292,17 @@ export class TallySlasherClient implements ProposerSlashActionProvider, SlasherC
 
     const committees = await this.collectCommitteesActiveDuringRound(slashedRound);
     const votes = getSlashConsensusVotesFromOffenses(offensesToSlash, committees, this.settings);
+    if (votes.every(v => v === 0)) {
+      this.log.warn(`Computed votes for offenses are all zero. Skipping vote.`, {
+        slotNumber,
+        currentRound,
+        slashedRound,
+        offensesToSlash,
+        committees,
+      });
+      return undefined;
+    }
+
     this.log.debug(`Computed votes for slashing ${offensesToSlash.length} offenses`, {
       slashedRound,
       currentRound,