feat: introduce operator fee for OP stack networks (#6979)

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## References

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## Checklist

- [ ] I've updated the test suite for new or updated code as appropriate
- [ ] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [ ] I've communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs),
highlighting breaking changes as necessary
- [ ] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Adds OP Stack operator fee to `layer1GasFee` by querying the oracle
(`getOperatorFee`) and summing with `getL1Fee`, plus BN utilities and
tests.
> 
> - **Layer 1 Gas Fee (oracle flow)**:
> - Sum oracle `getL1Fee` with operator fee from
`getOperatorFee(gasUsed)`; default operator fee to zero on
failure/undefined; output normalized hex via `add0x` +
`padHexToEvenLength`.
> - Refactor to BN-based math and value coercion via new `toBN`; extract
`#getGasPriceOracleContract`; keep default OP Stack oracle address and
optional signing.
>   - Extend ABI with `getOperatorFee`.
> - **Utils**:
>   - Add `bnFromHex` and `toBN` helpers for parsing/converting to `BN`.
> - **Tests**:
> - Update `OracleLayer1GasFeeFlow.test.ts` to mock BN returns and cover
operator fee present/failure/undefined paths.
>   - Add tests for `bnFromHex` and `toBN`.
> - **Docs**:
> - Update `CHANGELOG.md` to note inclusion of operator fee in
`layer1GasFee`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
6e8d304. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: pedronfigueiredo

packages/transaction-controller/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Calculate operator fee for OP stack networks and include it in `layer1GasFee` ([#6979](https://github.com/MetaMask/core/pull/6979))
+
 ## [61.1.0]
 
 ### Added

packages/transaction-controller/src/gas-flows/OracleLayer1GasFeeFlow.test.ts

@@ -2,13 +2,18 @@ import type { TypedTransaction } from '@ethereumjs/tx';
 import { TransactionFactory } from '@ethereumjs/tx';
 import { Contract } from '@ethersproject/contracts';
 import type { Provider } from '@metamask/network-controller';
-import type { Hex } from '@metamask/utils';
+import { add0x, type Hex } from '@metamask/utils';
+import BN from 'bn.js';
 
 import { OracleLayer1GasFeeFlow } from './OracleLayer1GasFeeFlow';
 import { CHAIN_IDS } from '../constants';
 import type { TransactionControllerMessenger } from '../TransactionController';
-import type { Layer1GasFeeFlowRequest, TransactionMeta } from '../types';
-import { TransactionStatus } from '../types';
+import {
+  type Layer1GasFeeFlowRequest,
+  type TransactionMeta,
+  TransactionStatus,
+} from '../types';
+import { bnFromHex, padHexToEvenLength } from '../utils/utils';
 
 jest.mock('@ethersproject/contracts', () => ({
   Contract: jest.fn(),
@@ -36,7 +41,8 @@ const TRANSACTION_META_MOCK: TransactionMeta = {
 
 const SERIALIZED_TRANSACTION_MOCK = '0x1234';
 const ORACLE_ADDRESS_MOCK = '0x5678' as Hex;
-const LAYER_1_FEE_MOCK = '0x9ABCD';
+const LAYER_1_FEE_MOCK = '0x09abcd';
+const OPERATOR_FEE_MOCK = '0x5';
 const DEFAULT_GAS_PRICE_ORACLE_ADDRESS =
   '0x420000000000000000000000000000000000000F';
 
@@ -98,9 +104,9 @@ class DefaultOracleLayer1GasFeeFlow extends OracleLayer1GasFeeFlow {
 
 describe('OracleLayer1GasFeeFlow', () => {
   const contractMock = jest.mocked(Contract);
-  const contractGetL1FeeMock: jest.MockedFn<
-    () => Promise<{ toHexString: () => string }>
-  > = jest.fn();
+  const contractGetL1FeeMock: jest.MockedFn<() => Promise<BN>> = jest.fn();
+  const contractGetOperatorFeeMock: jest.MockedFn<() => Promise<BN>> =
+    jest.fn();
 
   let request: Layer1GasFeeFlowRequest;
 
@@ -112,13 +118,14 @@ describe('OracleLayer1GasFeeFlow', () => {
 
     contractMock.mockClear();
     contractGetL1FeeMock.mockClear();
+    contractGetOperatorFeeMock.mockClear();
 
-    contractGetL1FeeMock.mockResolvedValue({
-      toHexString: () => LAYER_1_FEE_MOCK,
-    });
+    contractGetL1FeeMock.mockResolvedValue(bnFromHex(LAYER_1_FEE_MOCK));
+    contractGetOperatorFeeMock.mockResolvedValue(new BN(0));
 
     contractMock.mockReturnValue({
       getL1Fee: contractGetL1FeeMock,
+      getOperatorFee: contractGetOperatorFeeMock,
     } as unknown as Contract);
   });
 
@@ -156,6 +163,7 @@ describe('OracleLayer1GasFeeFlow', () => {
       expect(contractGetL1FeeMock).toHaveBeenCalledWith(
         serializedTransactionMock,
       );
+      expect(contractGetOperatorFeeMock).not.toHaveBeenCalled();
     });
 
     it('signs transaction with dummy key if supported by flow', async () => {
@@ -180,6 +188,7 @@ describe('OracleLayer1GasFeeFlow', () => {
       });
 
       expect(typedTransactionMock.sign).toHaveBeenCalledTimes(1);
+      expect(contractGetOperatorFeeMock).not.toHaveBeenCalled();
     });
 
     describe('throws', () => {
@@ -228,5 +237,79 @@ describe('OracleLayer1GasFeeFlow', () => {
       expect(oracleAddress).toBe(DEFAULT_GAS_PRICE_ORACLE_ADDRESS);
       expect(typedTransactionMock.sign).not.toHaveBeenCalled();
     });
+
+    it('adds operator fee when gas used is available', async () => {
+      const gasUsed = '0x5208';
+      request = {
+        ...request,
+        transactionMeta: {
+          ...request.transactionMeta,
+          gasUsed,
+        },
+      };
+
+      contractGetOperatorFeeMock.mockResolvedValueOnce(
+        bnFromHex(OPERATOR_FEE_MOCK),
+      );
+
+      const flow = new MockOracleLayer1GasFeeFlow(false);
+      const response = await flow.getLayer1Fee(request);
+
+      expect(contractGetOperatorFeeMock).toHaveBeenCalledTimes(1);
+      expect(contractGetOperatorFeeMock).toHaveBeenCalledWith(gasUsed);
+      expect(response).toStrictEqual({
+        layer1Fee: add0x(
+          padHexToEvenLength(
+            bnFromHex(LAYER_1_FEE_MOCK)
+              .add(bnFromHex(OPERATOR_FEE_MOCK))
+              .toString(16),
+          ),
+        ) as Hex,
+      });
+    });
+
+    it('defaults operator fee to zero when call fails', async () => {
+      const gasUsed = '0x1';
+      request = {
+        ...request,
+        transactionMeta: {
+          ...request.transactionMeta,
+          gasUsed,
+        },
+      };
+
+      contractGetOperatorFeeMock.mockRejectedValueOnce(new Error('revert'));
+
+      const flow = new MockOracleLayer1GasFeeFlow(false);
+      const response = await flow.getLayer1Fee(request);
+
+      expect(contractGetOperatorFeeMock).toHaveBeenCalledTimes(1);
+      expect(response).toStrictEqual({
+        layer1Fee: LAYER_1_FEE_MOCK,
+      });
+    });
+
+    it('defaults operator fee to zero when call returns undefined', async () => {
+      const gasUsed = '0x2';
+      request = {
+        ...request,
+        transactionMeta: {
+          ...request.transactionMeta,
+          gasUsed,
+        },
+      };
+
+      contractGetOperatorFeeMock.mockResolvedValueOnce(
+        undefined as unknown as BN,
+      );
+
+      const flow = new MockOracleLayer1GasFeeFlow(false);
+      const response = await flow.getLayer1Fee(request);
+
+      expect(contractGetOperatorFeeMock).toHaveBeenCalledTimes(1);
+      expect(response).toStrictEqual({
+        layer1Fee: LAYER_1_FEE_MOCK,
+      });
+    });
   });
 });

packages/transaction-controller/src/gas-flows/OracleLayer1GasFeeFlow.ts

@@ -1,7 +1,8 @@
 import { Contract } from '@ethersproject/contracts';
 import { Web3Provider, type ExternalProvider } from '@ethersproject/providers';
 import type { Hex } from '@metamask/utils';
-import { createModuleLogger } from '@metamask/utils';
+import { add0x, createModuleLogger } from '@metamask/utils';
+import BN from 'bn.js';
 
 import { projectLogger } from '../logger';
 import type { TransactionControllerMessenger } from '../TransactionController';
@@ -12,17 +13,52 @@ import type {
   TransactionMeta,
 } from '../types';
 import { prepareTransaction } from '../utils/prepare';
+import { padHexToEvenLength, toBN } from '../utils/utils';
 
 const log = createModuleLogger(projectLogger, 'oracle-layer1-gas-fee-flow');
 
+const ZERO = new BN(0);
+
 const DUMMY_KEY =
   'abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789';
 
 const GAS_PRICE_ORACLE_ABI = [
   {
-    inputs: [{ internalType: 'bytes', name: '_data', type: 'bytes' }],
+    inputs: [
+      {
+        internalType: 'bytes',
+        name: '_data',
+        type: 'bytes',
+      },
+    ],
     name: 'getL1Fee',
-    outputs: [{ internalType: 'uint256', name: '', type: 'uint256' }],
+    outputs: [
+      {
+        internalType: 'uint256',
+        name: '',
+        type: 'uint256',
+      },
+    ],
+    stateMutability: 'view',
+    type: 'function',
+  },
+  // only available post Isthmus
+  {
+    inputs: [
+      {
+        internalType: 'uint256',
+        name: '_gasUsed',
+        type: 'uint256',
+      },
+    ],
+    name: 'getOperatorFee',
+    outputs: [
+      {
+        internalType: 'uint256',
+        name: '',
+        type: 'uint256',
+      },
+    ],
     stateMutability: 'view',
     type: 'function',
   },
@@ -73,25 +109,37 @@ export abstract class OracleLayer1GasFeeFlow implements Layer1GasFeeFlow {
     request: Layer1GasFeeFlowRequest,
   ): Promise<Layer1GasFeeFlowResponse> {
     try {
-      return await this.#getOracleLayer1GasFee(request);
+      const { provider, transactionMeta } = request;
+
+      const contract = this.#getGasPriceOracleContract(
+        provider,
+        transactionMeta.chainId,
+      );
+
+      const oracleFee = await this.#getOracleLayer1GasFee(
+        contract,
+        transactionMeta,
+      );
+      const operatorFee = await this.#getOperatorLayer1GasFee(
+        contract,
+        transactionMeta,
+      );
+
+      return {
+        layer1Fee: add0x(
+          padHexToEvenLength(oracleFee.add(operatorFee).toString(16)),
+        ) as Hex,
+      };
     } catch (error) {
       log('Failed to get oracle layer 1 gas fee', error);
       throw new Error(`Failed to get oracle layer 1 gas fee`);
     }
   }
 
   async #getOracleLayer1GasFee(
-    request: Layer1GasFeeFlowRequest,
-  ): Promise<Layer1GasFeeFlowResponse> {
-    const { provider, transactionMeta } = request;
-
-    const contract = new Contract(
-      this.getOracleAddressForChain(transactionMeta.chainId),
-      GAS_PRICE_ORACLE_ABI,
-      // Network controller provider type is incompatible with ethers provider
-      new Web3Provider(provider as unknown as ExternalProvider),
-    );
-
+    contract: Contract,
+    transactionMeta: TransactionMeta,
+  ): Promise<BN> {
     const serializedTransaction = this.#buildUnserializedTransaction(
       transactionMeta,
       this.shouldSignTransaction(),
@@ -103,9 +151,31 @@ export abstract class OracleLayer1GasFeeFlow implements Layer1GasFeeFlow {
       throw new Error('No value returned from oracle contract');
     }
 
-    return {
-      layer1Fee: result.toHexString(),
-    };
+    return toBN(result);
+  }
+
+  async #getOperatorLayer1GasFee(
+    contract: Contract,
+    transactionMeta: TransactionMeta,
+  ): Promise<BN> {
+    const { gasUsed } = transactionMeta;
+
+    if (!gasUsed) {
+      return ZERO;
+    }
+
+    try {
+      const result = await contract.getOperatorFee(gasUsed);
+
+      if (result === undefined) {
+        return ZERO;
+      }
+
+      return toBN(result);
+    } catch (error) {
+      log('Failed to get operator layer 1 gas fee', error);
+      return ZERO;
+    }
   }
 
   #buildUnserializedTransaction(
@@ -134,4 +204,16 @@ export abstract class OracleLayer1GasFeeFlow implements Layer1GasFeeFlow {
       gasLimit: transactionMeta.txParams.gas,
     };
   }
+
+  #getGasPriceOracleContract(
+    provider: Layer1GasFeeFlowRequest['provider'],
+    chainId: Hex,
+  ) {
+    return new Contract(
+      this.getOracleAddressForChain(chainId),
+      GAS_PRICE_ORACLE_ABI,
+      // Network controller provider type is incompatible with ethers provider
+      new Web3Provider(provider as unknown as ExternalProvider),
+    );
+  }
 }