fix: avoid unnecessary calls draw() when no juror is available

contracts/deploy/upgrade-all.ts

@@ -81,7 +81,7 @@ const deployUpgradeAll: DeployFunction = async (hre: HardhatRuntimeEnvironment)
   await upgrade(disputeKitClassic, "initialize6", []);
   await upgrade(disputeTemplateRegistry, "initialize2", []);
   await upgrade(evidence, "initialize2", []);
-  await upgrade(core, "initialize4", []);
+  await upgrade(core, "initialize5", []);
   await upgrade(policyRegistry, "initialize2", []);
   await upgrade(sortition, "initialize3", []);
 };

contracts/scripts/keeperBot.ts

@@ -7,6 +7,7 @@ import { Cores, getContracts as getContractsForCoreType } from "./utils/contract
 
 let request: <T>(url: string, query: string) => Promise<T>; // Workaround graphql-request ESM import
 const { ethers } = hre;
+const MAX_DRAW_CALLS_WITHOUT_JURORS = 10;
 const MAX_DRAW_ITERATIONS = 30;
 const MAX_EXECUTE_ITERATIONS = 20;
 const MAX_DELAYED_STAKES_ITERATIONS = 50;
@@ -248,7 +249,19 @@ const drawJurors = async (dispute: { id: string; currentRoundIndex: string }, it
   const { core } = await getContracts();
   let success = false;
   try {
-    await core.draw.staticCall(dispute.id, iterations, HIGH_GAS_LIMIT);
+    const simulatedIterations = iterations * MAX_DRAW_CALLS_WITHOUT_JURORS; // Drawing will be skipped as long as no juror is available in the next MAX_DRAW_CALLS_WITHOUT_JURORS calls to draw() given this nb of iterations.
+    const { drawnJurors: drawnJurorsBefore } = await core.getRoundInfo(dispute.id, dispute.currentRoundIndex);
+    const nbDrawnJurors = (await core.draw.staticCall(dispute.id, simulatedIterations, HIGH_GAS_LIMIT)) as bigint;
+    const extraJurors = nbDrawnJurors - BigInt(drawnJurorsBefore.length);
+    logger.debug(
+      `Draw: ${extraJurors} jurors available in the next ${simulatedIterations} iterations for dispute ${dispute.id}`
+    );
+    if (extraJurors <= 0n) {
+      logger.warn(
+        `Draw: skipping, no jurors available in the next ${simulatedIterations} iterations for dispute ${dispute.id}`
+      );
+      return success;
+    }
   } catch (e) {
     logger.error(`Draw: will fail for ${dispute.id}, skipping`);
     return success;

contracts/src/arbitration/KlerosCoreBase.sol

@@ -593,7 +593,8 @@ abstract contract KlerosCoreBase is IArbitratorV2, Initializable, UUPSProxiable
     /// @dev Draws jurors for the dispute. Can be called in parts.
     /// @param _disputeID The ID of the dispute.
     /// @param _iterations The number of iterations to run.
-    function draw(uint256 _disputeID, uint256 _iterations) external {
+    /// @return nbDrawnJurors The total number of jurors drawn in the round.
+    function draw(uint256 _disputeID, uint256 _iterations) external returns (uint256 nbDrawnJurors) {
         Dispute storage dispute = disputes[_disputeID];
         uint256 currentRound = dispute.rounds.length - 1;
         Round storage round = dispute.rounds[currentRound];
@@ -616,6 +617,7 @@ abstract contract KlerosCoreBase is IArbitratorV2, Initializable, UUPSProxiable
             }
         }
         round.drawIterations += i;
+        return round.drawnJurors.length;
     }
 
     /// @dev Appeals the ruling of a specified dispute.

contracts/src/arbitration/KlerosCoreNeo.sol

@@ -9,7 +9,7 @@ import "@openzeppelin/contracts/token/ERC721/IERC721.sol";
 /// Core arbitrator contract for Kleros v2.
 /// Note that this contract trusts the PNK token, the dispute kit and the sortition module contracts.
 contract KlerosCoreNeo is KlerosCoreBase {
-    string public constant override version = "0.8.0";
+    string public constant override version = "0.9.0";
 
     // ************************************* //
     // *             Storage               * //
@@ -67,7 +67,7 @@ contract KlerosCoreNeo is KlerosCoreBase {
         jurorNft = _jurorNft;
     }
 
-    function initialize4() external reinitializer(4) {
+    function initialize5() external reinitializer(5) {
         // NOP
     }