feat: add reward call delegation

Implements an alternative discussed approach that allows orchestrators
to configure a custom reward caller.

Co-authored-by: SidestreamSweatyPumpkin <sweatypumpkin@sidestream.tech>

Author: rickstaa

.github/workflows/test.yaml

@@ -47,6 +47,9 @@ jobs:
           name: ${{ github.event.repository.name }}
           token: ${{ secrets.CI_CODECOV_TOKEN }}
 
+      - name: Enforce test coverage threshold
+        run: yarn test:coverage:check
+
   editorconfig:
     name: Run editorconfig checker
     runs-on: ubuntu-latest

contracts/bonding/BondingManager.sol

@@ -102,6 +102,9 @@ contract BondingManager is ManagerProxyTarget, IBondingManager {
     // If the balance of the treasury in LPT is above this value, automatic treasury contributions will halt.
     uint256 public treasuryBalanceCeiling;
 
+    // Allow reward() calls by pre-defined set of addresses
+    mapping(address => address) private rewardCallerToTranscoder;
+
     // Check if sender is TicketBroker
     modifier onlyTicketBroker() {
         _onlyTicketBroker();
@@ -188,6 +191,26 @@ contract BondingManager is ManagerProxyTarget, IBondingManager {
         emit ParameterUpdate("numActiveTranscoders");
     }
 
+    /**
+     * @notice Set a reward caller for a transcoder
+     * @param _rewardCaller Address of the new reward caller
+     */
+    function setRewardCaller(address _rewardCaller) external whenSystemNotPaused {
+        require(rewardCallerToTranscoder[_rewardCaller] == address(0), "reward caller is already set");
+        rewardCallerToTranscoder[_rewardCaller] = msg.sender;
+        emit RewardCallerSet(msg.sender, _rewardCaller);
+    }
+
+    /**
+     * @notice Unset a reward caller for a transcoder
+     * @param _rewardCaller Address of the existing reward caller
+     */
+    function unsetRewardCaller(address _rewardCaller) external whenSystemNotPaused {
+        require(rewardCallerToTranscoder[_rewardCaller] == msg.sender, "only relevant transcoder can unset");
+        rewardCallerToTranscoder[_rewardCaller] = address(0);
+        emit RewardCallerUnset(msg.sender, _rewardCaller);
+    }
+
     /**
      * @notice Sets commission rates as a transcoder and if the caller is not in the transcoder pool tries to add it
      * @dev Percentages are represented as numerators of fractions over MathUtils.PERC_DIVISOR
@@ -865,17 +888,20 @@ contract BondingManager is ManagerProxyTarget, IBondingManager {
         public
         whenSystemNotPaused
         currentRoundInitialized
-        autoCheckpoint(msg.sender)
     {
         uint256 currentRound = roundsManager().currentRound();
 
-        require(isActiveTranscoder(msg.sender), "caller must be an active transcoder");
+        address transcoderAddress = msg.sender;
+        if (!isActiveTranscoder(transcoderAddress)) {
+            transcoderAddress = rewardCallerToTranscoder[msg.sender];
+            require(isActiveTranscoder(transcoderAddress), "caller must be an active transcoder or rewardCaller");
+        }
         require(
-            transcoders[msg.sender].lastRewardRound != currentRound,
+            transcoders[transcoderAddress].lastRewardRound != currentRound,
             "caller has already called reward for the current round"
         );
 
-        Transcoder storage t = transcoders[msg.sender];
+        Transcoder storage t = transcoders[transcoderAddress];
         EarningsPool.Data storage earningsPool = t.earningsPoolPerRound[currentRound];
 
         // Set last round that transcoder called reward
@@ -908,17 +934,20 @@ contract BondingManager is ManagerProxyTarget, IBondingManager {
 
             mtr.trustedTransferTokens(trsry, treasuryRewards);
 
-            emit TreasuryReward(msg.sender, trsry, treasuryRewards);
+            emit TreasuryReward(transcoderAddress, trsry, treasuryRewards);
         }
 
         uint256 transcoderRewards = totalRewardTokens.sub(treasuryRewards);
 
-        updateTranscoderWithRewards(msg.sender, transcoderRewards, currentRound, _newPosPrev, _newPosNext);
+        updateTranscoderWithRewards(transcoderAddress, transcoderRewards, currentRound, _newPosPrev, _newPosNext);
 
         // Set last round that transcoder called reward
         t.lastRewardRound = currentRound;
 
-        emit Reward(msg.sender, transcoderRewards);
+        emit Reward(transcoderAddress, transcoderRewards);
+
+        // Manual execution of the `autoCheckpoint` modifier due to conditional nature of `transcoderAddress`
+        _checkpointBondingState(transcoderAddress, delegators[transcoderAddress], transcoders[transcoderAddress]);
     }
 
     /**

contracts/bonding/IBondingManager.sol

@@ -44,6 +44,8 @@ interface IBondingManager {
         uint256 startRound,
         uint256 endRound
     );
+    event RewardCallerSet(address indexed transcoder, address indexed rewardCaller);
+    event RewardCallerUnset(address indexed transcoder, address indexed rewardCaller);
 
     // Deprecated events
     // These event signatures can be used to construct the appropriate topic hashes to filter for past logs corresponding

package.json

@@ -21,6 +21,7 @@
     "clean": "rm -rf cache artifacts typechain",
     "compile": "npx hardhat compile",
     "test:coverage": "npx hardhat coverage",
+    "test:coverage:check": "npx istanbul check-coverage ./coverage.json --statements 100 --branches 100 --functions 100 --lines 100",
     "test": "npx hardhat test",
     "test:unit": "npx hardhat test test/unit/*.*",
     "test:integration": "npx hardhat test test/integration/**",

test/unit/BondingManager.js

@@ -5474,7 +5474,9 @@ describe("BondingManager", () => {
         it("should fail if caller is not a transcoder", async () => {
             await expect(
                 bondingManager.connect(nonTranscoder).reward()
-            ).to.be.revertedWith("caller must be an active transcoder")
+            ).to.be.revertedWith(
+                "caller must be an active transcoder or rewardCaller"
+            )
         })
 
         it("should fail if caller is registered but not an active transcoder yet in the current round", async () => {
@@ -5484,7 +5486,9 @@ describe("BondingManager", () => {
             )
             await expect(
                 bondingManager.connect(transcoder).reward()
-            ).to.be.revertedWith("caller must be an active transcoder")
+            ).to.be.revertedWith(
+                "caller must be an active transcoder or rewardCaller"
+            )
         })
 
         it("should fail if caller already called reward during the current round", async () => {
@@ -6100,6 +6104,150 @@ describe("BondingManager", () => {
                 atCeilingTest("when above limit", 1500)
             })
         })
+
+        describe("reward delegation", () => {
+            const transcoderRewards = 1000
+
+            it("should only allow active transcoders to set a RewardCaller", async () => {
+                const registeredTranscoder = signers[2]
+                await bondingManager
+                    .connect(registeredTranscoder)
+                    .bond(1000, registeredTranscoder.address)
+                await bondingManager
+                    .connect(registeredTranscoder)
+                    .transcoder(5, 10)
+
+                const registeredTranscoderTx = bondingManager
+                    .connect(registeredTranscoder)
+                    .setRewardCaller(nonTranscoder.address)
+
+                await expect(registeredTranscoderTx).to.be.revertedWith(
+                    "caller must be an active transcoder"
+                )
+
+                const activeTranscoderTx = bondingManager
+                    .connect(transcoder)
+                    .setRewardCaller(nonTranscoder.address)
+
+                await expect(activeTranscoderTx)
+                    .to.emit(bondingManager, "RewardCallerSet")
+                    .withArgs(transcoder.address, nonTranscoder.address)
+            })
+
+            it("should allow a transcoder to call reward even if RewardCaller is set", async () => {
+                const setRewardCallerTx = bondingManager
+                    .connect(transcoder)
+                    .setRewardCaller(nonTranscoder.address)
+                await expect(setRewardCallerTx)
+                    .to.emit(bondingManager, "RewardCallerSet")
+                    .withArgs(transcoder.address, nonTranscoder.address)
+
+                const rewardTx = bondingManager.connect(transcoder).reward()
+                await expect(rewardTx)
+                    .to.emit(bondingManager, "Reward")
+                    .withArgs(transcoder.address, transcoderRewards)
+
+                await fixture.roundsManager.setMockUint256(
+                    functionSig("currentRound()"),
+                    currentRound + 3
+                )
+
+                const unsetRewardCallerTx = bondingManager
+                    .connect(transcoder)
+                    .unsetRewardCaller(nonTranscoder.address)
+                await expect(unsetRewardCallerTx)
+                    .to.emit(bondingManager, "RewardCallerUnset")
+                    .withArgs(transcoder.address, nonTranscoder.address)
+
+                const rewardTx2 = bondingManager.connect(transcoder).reward()
+                await expect(rewardTx2)
+                    .to.emit(bondingManager, "Reward")
+                    .withArgs(transcoder.address, transcoderRewards)
+            })
+
+            it("should allow a RewardCaller to call reward", async () => {
+                const setRewardCallerTx = bondingManager
+                    .connect(transcoder)
+                    .setRewardCaller(nonTranscoder.address)
+                await expect(setRewardCallerTx)
+                    .to.emit(bondingManager, "RewardCallerSet")
+                    .withArgs(transcoder.address, nonTranscoder.address)
+
+                const rewardTx = bondingManager.connect(nonTranscoder).reward()
+                await expect(rewardTx)
+                    .to.emit(bondingManager, "Reward")
+                    .withArgs(transcoder.address, transcoderRewards)
+
+                await fixture.roundsManager.setMockUint256(
+                    functionSig("currentRound()"),
+                    currentRound + 3
+                )
+
+                const unsetRewardCallerTx = bondingManager
+                    .connect(transcoder)
+                    .unsetRewardCaller(nonTranscoder.address)
+                await expect(unsetRewardCallerTx)
+                    .to.emit(bondingManager, "RewardCallerUnset")
+                    .withArgs(transcoder.address, nonTranscoder.address)
+
+                const rewardTx2 = bondingManager.connect(nonTranscoder).reward()
+                await expect(rewardTx2).to.be.revertedWith(
+                    "caller must be an active transcoder or rewardCaller"
+                )
+            })
+
+            it("impossible to set the same RewardCaller twice", async () => {
+                const setRewardCallerTx = bondingManager
+                    .connect(transcoder)
+                    .setRewardCaller(nonTranscoder.address)
+                await expect(setRewardCallerTx)
+                    .to.emit(bondingManager, "RewardCallerSet")
+                    .withArgs(transcoder.address, nonTranscoder.address)
+
+                const setRewardCallerTx2 = bondingManager
+                    .connect(transcoder)
+                    .setRewardCaller(nonTranscoder.address)
+                await expect(setRewardCallerTx2).to.be.revertedWith(
+                    "reward caller is already set"
+                )
+            })
+
+            it("impossible to unset the RewardCaller for another transcoder", async () => {
+                const setRewardCallerTx = bondingManager
+                    .connect(transcoder)
+                    .setRewardCaller(nonTranscoder.address)
+                await expect(setRewardCallerTx)
+                    .to.emit(bondingManager, "RewardCallerSet")
+                    .withArgs(transcoder.address, nonTranscoder.address)
+
+                const unsetRewardCallerTx = bondingManager
+                    .connect(nonTranscoder)
+                    .unsetRewardCaller(nonTranscoder.address)
+                await expect(unsetRewardCallerTx).to.be.revertedWith(
+                    "only relevant transcoder can unset"
+                )
+            })
+
+            it("should always checkpoint the reward recipient, not the RewardCaller", async () => {
+                await bondingManager
+                    .connect(transcoder)
+                    .setRewardCaller(nonTranscoder.address)
+
+                const rewardCallerTx = await bondingManager
+                    .connect(nonTranscoder)
+                    .reward()
+
+                await expectCheckpoints(fixture, rewardCallerTx, {
+                    account: transcoder.address,
+                    startRound: currentRound + 2,
+                    bondedAmount: 1000,
+                    delegateAddress: transcoder.address,
+                    delegatedAmount: 2000,
+                    lastClaimRound: currentRound,
+                    lastRewardRound: currentRound + 1
+                })
+            })
+        })
     })
 
     describe("updateTranscoderWithFees", () => {