feat: add Gas burner contract to enable Gas Sponsorship testing in edges

contracts/SponsorshipProbe.sol

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+/// Used to test Paid by MetaMask on a sponsored network.
+/// `burn` writes one storage slot per iteration and succeeds.
+contract SponsorshipProbe {
+    mapping(uint256 => uint256) public slots;
+
+    function burn(uint256 iterations) external {
+        for (uint256 i = 0; i < iterations; i++) {
+            slots[i] = i + 1;
+        }
+    }
+}

src/components/transactions/index.js

@@ -3,5 +3,6 @@ export * from './erc20';
 export * from './erc721';
 export * from './erc1155';
 export * from './send';
+export * from './sponsorship';
 export * from './swapComparison';
 export * from './batchUsdcSwap';

src/components/transactions/sponsorship-probe.js

@@ -0,0 +1,22 @@
+// Compiled from contracts/SponsorshipProbe.sol (solc 0.8.20, optimizer on).
+// Each burn iteration writes a fresh storage slot, about 22,000 gas.
+
+export const sponsorshipProbeAbi = [
+  {
+    inputs: [{ internalType: 'uint256', name: 'iterations', type: 'uint256' }],
+    name: 'burn',
+    outputs: [],
+    stateMutability: 'nonpayable',
+    type: 'function',
+  },
+  {
+    inputs: [{ internalType: 'uint256', name: '', type: 'uint256' }],
+    name: 'slots',
+    outputs: [{ internalType: 'uint256', name: '', type: 'uint256' }],
+    stateMutability: 'view',
+    type: 'function',
+  },
+];
+
+export const sponsorshipProbeBytecode =
+  '0x608060405234801561000f575f80fd5b506101498061001d5f395ff3fe608060405234801561000f575f80fd5b5060043610610034575f3560e01c8063387dd9e91461003857806342966c6814610069575b5f80fd5b6100576100463660046100b7565b5f6020819052908152604090205481565b60405190815260200160405180910390f35b61007c6100773660046100b7565b61007e565b005b5f5b818110156100b3576100938160016100e2565b5f82815260208190526040902055806100ab816100fb565b915050610080565b5050565b5f602082840312156100c7575f80fd5b5035919050565b634e487b7160e01b5f52601160045260245ffd5b808201808211156100f5576100f56100ce565b92915050565b5f6001820161010c5761010c6100ce565b506001019056fea2646970667358221220ee70631fccc4a34563b5efe275f5808a50f5af0440ba77a09493bbb5ecf5fd3664736f6c63430008140033';

src/components/transactions/sponsorship.js

@@ -0,0 +1,172 @@
+import { ethers } from 'ethers';
+import globalContext from '../..';
+import {
+  sponsorshipProbeAbi,
+  sponsorshipProbeBytecode,
+} from './sponsorship-probe';
+
+// Cold SSTORE of a zero slot is 20,000, plus the cold-account access.
+const GAS_PER_ITERATION = 22000;
+const MAX_ITERATIONS = 500;
+
+const probeInterface = new ethers.utils.Interface(sponsorshipProbeAbi);
+
+export function sponsorshipComponent(parentContainer) {
+  parentContainer.insertAdjacentHTML(
+    'beforeend',
+    `<div class="col-xl-4 col-lg-6 col-md-12 col-sm-12 col-12 d-flex align-items-stretch">
+        <div class="card full-width">
+            <div class="card-body">
+            <h4 class="card-title">
+                Paid by MetaMask
+            </h4>
+            <p class="info-text alert alert-secondary">
+                Use on Monad with an upgraded account to test Gas Sponsorship.
+            </p>
+
+            <button
+                class="btn btn-primary btn-lg btn-block mb-3"
+                id="deploySponsorshipProbeButton"
+                disabled
+            >
+                Deploy gas burner
+            </button>
+
+            <p class="info-text alert alert-secondary">
+                Contract: <span id="sponsorshipAddress" style="word-break: break-all;">Not deployed</span>
+            </p>
+
+            <div class="form-group">
+                <label for="sponsorshipIterations">
+                    Storage writes (~22k gas each)
+                </label>
+                <input
+                    class="form-control"
+                    type="number"
+                    id="sponsorshipIterations"
+                    value="100"
+                    min="1"
+                    max="${MAX_ITERATIONS}"
+                />
+            </div>
+
+            <button
+                class="btn btn-primary btn-lg btn-block mb-3"
+                id="burnGasButton"
+                disabled
+            >
+                Burn gas
+            </button>
+
+            <p class="info-text alert alert-secondary">
+                Status: <span id="sponsorshipStatus">Not clicked</span>
+            </p>
+            </div>
+        </div>
+    </div>`,
+  );
+
+  const deployButton = document.getElementById('deploySponsorshipProbeButton');
+  const burnGasButton = document.getElementById('burnGasButton');
+  const iterationsInput = document.getElementById('sponsorshipIterations');
+  const contractAddress = document.getElementById('sponsorshipAddress');
+  const status = document.getElementById('sponsorshipStatus');
+
+  let probeContract;
+
+  document.addEventListener('globalConnectionChange', (event) => {
+    if (event.detail.connected) {
+      deployButton.disabled = false;
+    }
+  });
+
+  document.addEventListener('disableAndClear', () => {
+    deployButton.disabled = true;
+    burnGasButton.disabled = true;
+    probeContract = undefined;
+    contractAddress.innerHTML = 'Not deployed';
+  });
+
+  document.addEventListener('newChainIdInt', () => {
+    if (!probeContract) {
+      return;
+    }
+    probeContract = undefined;
+    burnGasButton.disabled = true;
+    contractAddress.innerHTML = 'Not deployed';
+    status.innerHTML = 'Network changed. Deploy the gas burner again.';
+  });
+
+  const readIterations = () => {
+    const iterations = Number.parseInt(iterationsInput.value, 10);
+    if (
+      !Number.isInteger(iterations) ||
+      iterations < 1 ||
+      iterations > MAX_ITERATIONS
+    ) {
+      throw new Error(
+        `Iterations must be an integer from 1 to ${MAX_ITERATIONS}.`,
+      );
+    }
+    return iterations;
+  };
+
+  deployButton.onclick = async () => {
+    status.innerHTML = 'Deploying';
+    burnGasButton.disabled = true;
+    try {
+      const factory = new ethers.ContractFactory(
+        sponsorshipProbeAbi,
+        sponsorshipProbeBytecode,
+        globalContext.ethersProvider.getSigner(),
+      );
+      const deployed = await factory.deploy();
+      await deployed.deployTransaction.wait();
+      if (!deployed.address) {
+        status.innerHTML = 'Deployment failed';
+        burnGasButton.disabled = !probeContract;
+        return;
+      }
+
+      probeContract = deployed;
+      burnGasButton.disabled = false;
+      contractAddress.innerHTML = deployed.address;
+      status.innerHTML = 'Deployed';
+      console.log(
+        `Sponsorship probe mined at ${deployed.address} tx ${deployed.deployTransaction.hash}`,
+      );
+    } catch (error) {
+      status.innerHTML = error.message || 'Deployment failed';
+      burnGasButton.disabled = !probeContract;
+      console.log('error', error);
+      throw error;
+    }
+  };
+
+  burnGasButton.onclick = async () => {
+    try {
+      if (!probeContract) {
+        throw new Error('Deploy the gas burner first.');
+      }
+      const iterations = readIterations();
+      const approximateGas = iterations * GAS_PER_ITERATION;
+      status.innerHTML = `Waiting for confirmation. About ${approximateGas} gas, no gas limit on the request.`;
+      const txHash = await globalContext.provider.request({
+        method: 'eth_sendTransaction',
+        params: [
+          {
+            from: globalContext.accounts[0],
+            to: probeContract.address,
+            data: probeInterface.encodeFunctionData('burn', [iterations]),
+          },
+        ],
+      });
+      status.innerHTML = `Submitted ${txHash}. About ${approximateGas} gas was executed. Compare gasUsed on the explorer.`;
+      console.log('burn gas', txHash);
+    } catch (error) {
+      status.innerHTML = error.message || 'Burn failed';
+      console.log('error', error);
+      throw error;
+    }
+  };
+}

src/index.js

@@ -16,6 +16,7 @@ import {
 } from './components/connections';
 import {
   sendComponent,
+  sponsorshipComponent,
   erc20Component,
   erc1155Component,
   eip747Component,
@@ -184,6 +185,7 @@ const transactionsRow = document.createElement('div');
 transactionsRow.className = 'row';
 transactionsSection.appendChild(transactionsRow);
 sendComponent(transactionsRow);
+sponsorshipComponent(transactionsRow);
 erc20Component(transactionsRow);
 erc721Component(transactionsRow);
 erc1155Component(transactionsRow);