fix!: fee estimation for multicall (#2034)

.changeset/shy-apricots-suffer.md

@@ -0,0 +1,5 @@
+---
+"@fuel-ts/account": minor
+---
+
+fix!: fee estimation for multicall

packages/abi-coder/src/index.ts

@@ -22,6 +22,8 @@ export {
   WORD_SIZE,
   ASSET_ID_LEN,
   CONTRACT_ID_LEN,
+  UTXO_ID_LEN,
+  BYTES_32,
   calculateVmTxMemory,
   type EncodingVersion,
   ENCODING_V0,

packages/abi-coder/src/utils/constants.ts

@@ -33,6 +33,7 @@ export const ENCODING_V1 = '1';
  */
 export const WORD_SIZE = 8;
 export const BYTES_32 = 32;
+export const UTXO_ID_LEN = BYTES_32 + 1;
 export const MAX_INPUTS = 255;
 export const ASSET_ID_LEN = BYTES_32;
 export const CONTRACT_ID_LEN = BYTES_32;

packages/account/src/providers/provider.test.ts

@@ -1007,12 +1007,11 @@ describe('Provider', () => {
       .spyOn(gasMod, 'calculatePriceWithFactor')
       .mockReturnValue(bn(0));
 
-    const { minFee, maxFee, usedFee } = await provider.getTransactionCost(request);
+    const { minFee, maxFee } = await provider.getTransactionCost(request);
 
-    expect(calculatePriceWithFactorMock).toHaveBeenCalledTimes(3);
+    expect(calculatePriceWithFactorMock).toHaveBeenCalled();
 
     expect(maxFee.eq(0)).not.toBeTruthy();
-    expect(usedFee.eq(0)).not.toBeTruthy();
     expect(minFee.eq(0)).not.toBeTruthy();
   });
 

packages/account/src/providers/provider.ts

@@ -150,7 +150,6 @@ export type TransactionCost = {
   gasUsed: BN;
   minFee: BN;
   maxFee: BN;
-  usedFee: BN;
   outputVariables: number;
   missingContractIds: string[];
   estimatedInputs: TransactionRequest['inputs'];
@@ -775,6 +774,58 @@ export default class Provider {
     };
   }
 
+  /**
+   * Estimates the transaction gas and fee based on the provided transaction request.
+   * @param transactionRequest - The transaction request object.
+   * @returns An object containing the estimated minimum gas, minimum fee, maximum gas, and maximum fee.
+   */
+  estimateTxGasAndFee(params: { transactionRequest: TransactionRequest }) {
+    const { transactionRequest } = params;
+    const { gasPriceFactor, minGasPrice, maxGasPerTx } = this.getGasConfig();
+
+    const chainInfo = this.getChain();
+
+    const gasPrice = transactionRequest.gasPrice.eq(0) ? minGasPrice : transactionRequest.gasPrice;
+    transactionRequest.gasPrice = gasPrice;
+
+    const minGas = transactionRequest.calculateMinGas(chainInfo);
+    const minFee = calculatePriceWithFactor(minGas, gasPrice, gasPriceFactor).normalizeZeroToOne();
+
+    // Only Script transactions consume gas
+    if (transactionRequest.type === TransactionType.Script) {
+      // If the gasLimit is set to 0, it means we need to estimate it.
+      if (transactionRequest.gasLimit.eq(0)) {
+        transactionRequest.gasLimit = minGas;
+
+        /*
+         * Adjusting the gasLimit of a transaction (TX) impacts its maxGas.
+         * Consequently, this affects the maxFee, as it is derived from the maxGas. To accurately estimate the
+         * gasLimit for a transaction, especially when the exact gas consumption is uncertain (as in an estimation dry-run),
+         * the following steps are required:
+         * 1 - Initially, set the gasLimit using the calculated minGas.
+         * 2 - Based on this initial gasLimit, calculate the maxGas.
+         * 3 - Get the maximum gas per transaction allowed by the chain, and subtract the previously calculated maxGas from this limit.
+         * 4 - The result of this subtraction should then be adopted as the new, definitive gasLimit.
+         * 5 - Recalculate the maxGas with the updated gasLimit. This new maxGas is then used to compute the maxFee.
+         * 6 - The calculated maxFee represents the safe, estimated cost required to fund the transaction.
+         */
+        transactionRequest.gasLimit = maxGasPerTx.sub(
+          transactionRequest.calculateMaxGas(chainInfo, minGas)
+        );
+      }
+    }
+
+    const maxGas = transactionRequest.calculateMaxGas(chainInfo, minGas);
+    const maxFee = calculatePriceWithFactor(maxGas, gasPrice, gasPriceFactor).normalizeZeroToOne();
+
+    return {
+      minGas,
+      minFee,
+      maxGas,
+      maxFee,
+    };
+  }
+
   /**
    * Executes a signed transaction without applying the states changes
    * on the chain.
@@ -830,9 +881,8 @@ export default class Provider {
     }: TransactionCostParams = {}
   ): Promise<TransactionCost> {
     const txRequestClone = clone(transactionRequestify(transactionRequestLike));
-    const chainInfo = this.getChain();
-    const { gasPriceFactor, minGasPrice, maxGasPerTx } = this.getGasConfig();
-    const gasPrice = max(txRequestClone.gasPrice, minGasPrice);
+    const { minGasPrice } = this.getGasConfig();
+    const setGasPrice = max(txRequestClone.gasPrice, minGasPrice);
     const isScriptTransaction = txRequestClone.type === TransactionType.Script;
 
     // Fund with fake UTXOs to avoid not enough funds error
@@ -843,15 +893,14 @@ export default class Provider {
     // Funding transaction with fake utxos
     txRequestClone.fundWithFakeUtxos(allQuantities, resourcesOwner?.address);
 
+    if (isScriptTransaction) {
+      txRequestClone.gasLimit = bn(0);
+    }
+
     /**
      * Estimate predicates gasUsed
      */
     if (estimatePredicates) {
-      // Remove gasLimit to avoid gasLimit when estimating predicates
-      if (isScriptTransaction) {
-        txRequestClone.gasLimit = bn(0);
-      }
-
       /**
        * The fake utxos added above can be from a predicate
        * If the resources owner is a predicate,
@@ -871,16 +920,17 @@ export default class Provider {
     /**
      * Calculate minGas and maxGas based on the real transaction
      */
-    const minGas = txRequestClone.calculateMinGas(chainInfo);
-    const maxGas = txRequestClone.calculateMaxGas(chainInfo, minGas);
+    let { maxFee, maxGas, minFee, minGas } = this.estimateTxGasAndFee({
+      transactionRequest: txRequestClone,
+    });
 
     /**
      * Estimate gasUsed for script transactions
      */
-
     let receipts: TransactionResultReceipt[] = [];
     let missingContractIds: string[] = [];
     let outputVariables = 0;
+    let gasUsed = bn(0);
     // Transactions of type Create does not consume any gas so we can the dryRun
     if (isScriptTransaction && estimateTxDependencies) {
       /**
@@ -889,39 +939,34 @@ export default class Provider {
        * will only be amounts being transferred (coin outputs) and amounts being forwarded
        * to contract calls.
        */
-      // Calculate the gasLimit again as we insert a fake UTXO and signer
-
       txRequestClone.gasPrice = bn(0);
-      txRequestClone.gasLimit = bn(maxGasPerTx.sub(maxGas).toNumber() * 0.9);
 
       // Executing dryRun with fake utxos to get gasUsed
       const result = await this.estimateTxDependencies(txRequestClone);
 
       receipts = result.receipts;
       outputVariables = result.outputVariables;
       missingContractIds = result.missingContractIds;
-    }
 
-    // For CreateTransaction the gasUsed is going to be the minGas
-    const gasUsed = isScriptTransaction ? getGasUsedFromReceipts(receipts) : minGas;
+      gasUsed = isScriptTransaction ? getGasUsedFromReceipts(receipts) : gasUsed;
 
-    const usedFee = calculatePriceWithFactor(
-      gasUsed,
-      gasPrice,
-      gasPriceFactor
-    ).normalizeZeroToOne();
-    const minFee = calculatePriceWithFactor(minGas, gasPrice, gasPriceFactor).normalizeZeroToOne();
-    const maxFee = calculatePriceWithFactor(maxGas, gasPrice, gasPriceFactor).normalizeZeroToOne();
+      txRequestClone.gasLimit = gasUsed;
+      txRequestClone.gasPrice = setGasPrice;
+
+      // Estimating fee again with the real gas consumed and set gasPrice
+      ({ maxFee, maxGas, minFee, minGas } = this.estimateTxGasAndFee({
+        transactionRequest: txRequestClone,
+      }));
+    }
 
     return {
       requiredQuantities: allQuantities,
       receipts,
       gasUsed,
       minGasPrice,
-      gasPrice,
+      gasPrice: setGasPrice,
       minGas,
       maxGas,
-      usedFee,
       minFee,
       maxFee,
       estimatedInputs: txRequestClone.inputs,

packages/account/src/providers/transaction-request/input.ts

@@ -1,3 +1,4 @@
+import { BYTES_32, UTXO_ID_LEN } from '@fuel-ts/abi-coder';
 import { ZeroBytes32 } from '@fuel-ts/address/configs';
 import { ErrorCode, FuelError } from '@fuel-ts/errors';
 import type { BytesLike } from '@fuel-ts/interfaces';
@@ -96,8 +97,8 @@ export const inputify = (value: TransactionRequestInput): Input => {
       const predicateData = arrayify(value.predicateData ?? '0x');
       return {
         type: InputType.Coin,
-        txID: hexlify(arrayify(value.id).slice(0, 32)),
-        outputIndex: arrayify(value.id)[32],
+        txID: hexlify(arrayify(value.id).slice(0, BYTES_32)),
+        outputIndex: toNumber(arrayify(value.id).slice(BYTES_32, UTXO_ID_LEN)),
         owner: hexlify(value.owner),
         amount: bn(value.amount),
         assetId: hexlify(value.assetId),

packages/account/src/providers/transaction-request/transaction-request.ts

@@ -1,6 +1,8 @@
 import type { InputValue } from '@fuel-ts/abi-coder';
+import { UTXO_ID_LEN } from '@fuel-ts/abi-coder';
 import { Address, addressify } from '@fuel-ts/address';
 import { BaseAssetId, ZeroBytes32 } from '@fuel-ts/address/configs';
+import { randomBytes } from '@fuel-ts/crypto';
 import type { AddressLike, AbstractAddress, BytesLike } from '@fuel-ts/interfaces';
 import type { BN, BigNumberish } from '@fuel-ts/math';
 import { bn } from '@fuel-ts/math';
@@ -596,13 +598,6 @@ export abstract class BaseTransactionRequest implements BaseTransactionRequestLi
    * @param quantities - CoinQuantity Array.
    */
   fundWithFakeUtxos(quantities: CoinQuantity[], resourcesOwner?: AbstractAddress) {
-    let idCounter = 0;
-    const generateId = (): string => {
-      const counterString = String(idCounter++);
-      const id = ZeroBytes32.slice(0, -counterString.length).concat(counterString);
-      return id;
-    };
-
     const findAssetInput = (assetId: string) =>
       this.inputs.find((input) => {
         if ('assetId' in input) {
@@ -615,12 +610,12 @@ export abstract class BaseTransactionRequest implements BaseTransactionRequestLi
       const assetInput = findAssetInput(assetId);
 
       if (assetInput && 'assetId' in assetInput) {
-        assetInput.id = generateId();
+        assetInput.id = hexlify(randomBytes(UTXO_ID_LEN));
         assetInput.amount = quantity;
       } else {
         this.addResources([
           {
-            id: generateId(),
+            id: hexlify(randomBytes(UTXO_ID_LEN)),
             amount: quantity,
             assetId,
             owner: resourcesOwner || Address.fromRandom(),

packages/fuel-gauge/src/fee.test.ts

@@ -10,6 +10,7 @@ import {
   ScriptTransactionRequest,
   Wallet,
   bn,
+  getRandomB256,
 } from 'fuels';
 
 import { FuelGaugeProjectsEnum, getFuelGaugeForcProject } from '../test/fixtures';
@@ -254,6 +255,42 @@ describe('Fee', () => {
     });
   });
 
+  it('should ensure fee is properly calculated in a multi call [MINT TO 15 ADDRESSES]', async () => {
+    const { binHexlified, abiContents } = getFuelGaugeForcProject(
+      FuelGaugeProjectsEnum.MULTI_TOKEN_CONTRACT
+    );
+
+    const factory = new ContractFactory(binHexlified, abiContents, wallet);
+    const contract = await factory.deployContract({ gasPrice: minGasPrice });
+
+    const subId = '0x4a778acfad1abc155a009dc976d2cf0db6197d3d360194d74b1fb92b96986b00';
+
+    const genAddresses = () => Array.from({ length: 3 }, () => ({ value: getRandomB256() }));
+
+    const calls = Array.from({ length: 15 }).map(() =>
+      contract.functions.mint_to_addresses(genAddresses(), subId, 100)
+    );
+
+    const balanceBefore = await wallet.getBalance();
+
+    const {
+      transactionResult: { fee },
+    } = await contract
+      .multiCall(calls)
+      .txParams({ variableOutputs: calls.length * 3 })
+      .call();
+
+    const balanceAfter = await wallet.getBalance();
+
+    const balanceDiff = balanceBefore.sub(balanceAfter).toNumber();
+
+    expectToBeInRange({
+      value: fee.toNumber(),
+      min: balanceDiff - 1,
+      max: balanceDiff + 1,
+    });
+  });
+
   it('should ensure fee is properly calculated on transactions with predicate', async () => {
     const { binHexlified, abiContents } = getFuelGaugeForcProject(
       FuelGaugeProjectsEnum.PREDICATE_TRUE

packages/fuel-gauge/src/funding-transaction.test.ts

@@ -74,12 +74,13 @@ describe(__filename, () => {
 
     request.addResources(lowResources);
 
-    const { maxFee, requiredQuantities } = await provider.getTransactionCost(request);
+    const { maxFee, requiredQuantities, gasUsed } = await provider.getTransactionCost(request);
+
+    request.gasLimit = gasUsed;
 
     // TX request already does NOT carries enough resources, it needs to be funded
     expect(request.inputs.length).toBe(1);
     expect(bn((<CoinTransactionRequestInput>request.inputs[0]).amount).toNumber()).toBe(300);
-    expect(maxFee.gt(300)).toBeTruthy();
 
     const getResourcesToSpendSpy = vi.spyOn(sender, 'getResourcesToSpend');
 
@@ -161,19 +162,21 @@ describe(__filename, () => {
 
     const request = new ScriptTransactionRequest({
       gasLimit: 1_000,
-      gasPrice: bn(10),
+      gasPrice: bn(1),
     });
 
     const amountToTransfer = 1000;
     request.addCoinOutput(receiver.address, amountToTransfer, BaseAssetId);
 
-    const { maxFee, requiredQuantities } = await provider.getTransactionCost(request);
+    const { maxFee, requiredQuantities, gasUsed } = await provider.getTransactionCost(request);
 
     // TX request does NOT carry any resources, it needs to be funded
     expect(request.inputs.length).toBe(0);
 
     const getResourcesToSpendSpy = vi.spyOn(sender, 'getResourcesToSpend');
 
+    request.gasLimit = gasUsed;
+
     await sender.fund(request, requiredQuantities, maxFee);
 
     const tx = await sender.sendTransaction(request);

packages/fuel-gauge/src/min-gas.test.ts

@@ -86,12 +86,13 @@ describe(__filename, () => {
     /**
      * Get the transaction cost to set a strict gasLimit and min gasPrice
      */
-    const costs = await provider.getTransactionCost(request);
+    const { maxFee, gasUsed, requiredQuantities, minGasPrice } =
+      await provider.getTransactionCost(request);
 
-    await sender.fund(request, costs.requiredQuantities, costs.maxFee);
+    request.gasLimit = gasUsed;
+    request.gasPrice = minGasPrice;
 
-    request.gasLimit = bn(20_000);
-    request.gasPrice = costs.gasPrice;
+    await sender.fund(request, requiredQuantities, maxFee);
 
     /**
      * Send transaction
@@ -100,7 +101,7 @@ describe(__filename, () => {
     const { status, gasUsed: txGasUsed } = await result.wait();
 
     expect(status).toBe(TransactionStatus.success);
-    expect(costs.gasUsed.toString()).toBe(txGasUsed.toString());
+    expect(gasUsed.toString()).toBe(txGasUsed.toString());
   });
 
   it('sets gas requirements (predicate)', async () => {