Fix Ethereum post-dispatch weight (#1807)

* Add integration test

* Bump frontier to 5b682d4

* Fix test expected weight

tests/tests/test-eth-fee/test-eth-txn-weights.ts

@@ -0,0 +1,44 @@
+import "@moonbeam-network/api-augment";
+
+import { expect } from "chai";
+import { ethers } from "ethers";
+
+import { alith, ALITH_PRIVATE_KEY } from "../../util/accounts";
+import { getCompiled } from "../../util/contracts";
+import { customWeb3Request } from "../../util/providers";
+import { describeDevMoonbeamAllEthTxTypes, DevTestContext } from "../../util/setup-dev-tests";
+import { EXTRINSIC_GAS_LIMIT } from "../../util/constants";
+
+// This tests an issue where pallet Ethereum in Frontier does not properly account for weight after
+// transaction application. Specifically, it accounts for weight before a transaction by multiplying
+// GasToWeight by gas_price, but does not adjust this afterwards. This leads to accounting for too
+// much weight in a block.
+describeDevMoonbeamAllEthTxTypes("Ethereum Weight Accounting", (context) => {
+  it("should account for weight used", async function () {
+    this.timeout(10000);
+
+    let signer = new ethers.Wallet(ALITH_PRIVATE_KEY, context.ethers);
+
+    let tx = await signer.signTransaction({
+      from: alith.address,
+      to: null,
+      value: "0x0",
+      gasLimit: EXTRINSIC_GAS_LIMIT,
+      gasPrice: 1_000_000_000,
+      data: null,
+      nonce: await context.web3.eth.getTransactionCount(alith.address),
+    });
+
+    // TODO: tweak: this includes some priority fee. it would be more clear without this.
+    const expected_weight = 1_575_000_000;
+
+    const { block } = await context.createBlock(tx);
+
+    const apiAt = await context.polkadotApi.at(block.hash);
+
+    let blockWeightsUsed = await apiAt.query.system.blockWeight();
+    let normalWeight = blockWeightsUsed.normal;
+
+    expect(normalWeight.toNumber()).to.equal(expected_weight);
+  });
+});