Fix hardhat_reset (#667) and add unit tests

package.json

@@ -48,11 +48,16 @@
     "@nomiclabs/buidler": "^1.3.6",
     "@nomiclabs/buidler-truffle5": "^1.3.4",
     "@nomiclabs/buidler-web3": "^1.3.4",
+    "@nomiclabs/hardhat-ethers": "^2.0.4",
     "@nomiclabs/hardhat-truffle5": "^2.0.0",
+    "@nomiclabs/hardhat-waffle": "^2.0.1",
     "@nomiclabs/hardhat-web3": "^2.0.0",
     "@truffle/contract": "^4.0.36",
     "buidler-gas-reporter": "^0.1.3",
+    "chai": "^4.3.4",
     "decache": "^4.5.1",
+    "ethereum-waffle": "^3.4.0",
+    "ethers": "^5.5.3",
     "hardhat": "^2.8.2",
     "hardhat-gas-reporter": "^1.0.1",
     "mocha": "5.2.0",

plugins/hardhat.plugin.js

@@ -8,7 +8,7 @@ const path = require('path');
 
 const { task, types } = require("hardhat/config");
 const { HardhatPluginError } = require("hardhat/plugins")
-
+const {HARDHAT_NETWORK_RESET_EVENT} = require("hardhat/internal/constants");
 const {
   TASK_TEST,
   TASK_COMPILE,
@@ -162,12 +162,18 @@ task("coverage", "Generates a code coverage report for tests")
     // ==============
     // Server launch
     // ==============
-    const network = nomiclabsUtils.setupHardhatNetwork(env, api, ui);
+    let network = nomiclabsUtils.setupHardhatNetwork(env, api, ui);
 
     if (network.isHardhatEVM){
       accounts = await utils.getAccountsHardhat(network.provider);
       nodeInfo = await utils.getNodeInfoHardhat(network.provider);
 
+      // Note: this only works if the reset block number is before any transactions have fired on the fork.
+      // e.g you cannot fork at block 1, send some txs (blocks 2,3,4) and reset to block 2
+      env.network.provider.on(HARDHAT_NETWORK_RESET_EVENT, () => {
+        api.attachToHardhatVM(env.network.provider);
+      });
+
       api.attachToHardhatVM(network.provider);
 
       ui.report('hardhat-network', [

test/integration/projects/hardhat-reset/.solcover.js

@@ -0,0 +1,8 @@
+// Testing hooks
+const fn = (msg, config) => config.logger.log(msg);
+
+module.exports = {
+  skipFiles: ['Migrations.sol'],
+  silent: process.env.SILENT ? true : false,
+  istanbulReporter: ['json-summary', 'text'],
+}

test/integration/projects/hardhat-reset/contracts/ContractAReset.sol

@@ -0,0 +1,26 @@
+pragma solidity ^0.7.0;
+
+
+contract ContractA {
+  uint x;
+  constructor() public {
+  }
+
+  function sendFn() public {
+    x = 1;
+  }
+
+  function sendFn2() public {
+    x = 2;
+  }
+
+  function callFn() public pure returns (uint){
+    uint y = 5;
+    return y;
+  }
+
+  function callFn2() public pure returns (uint){
+    uint y = 5;
+    return y;
+  }
+}

test/integration/projects/hardhat-reset/hardhat.config.js

@@ -0,0 +1,28 @@
+require("@nomiclabs/hardhat-waffle");
+require("@nomiclabs/hardhat-ethers");
+require(__dirname + "/../plugins/nomiclabs.plugin");
+
+if (!process.env.ALCHEMY_TOKEN){
+  throw new Error(
+    "This test requires that you set ALCHEMY_TOKEN to a valid token in your development env"
+  );
+}
+
+module.exports = {
+  solidity: {
+    version: "0.7.0"
+  },
+  networks: {
+    hardhat: {
+      timeout: 100000,
+      forking: {
+        url: `https://eth-mainnet.alchemyapi.io/v2/${process.env.ALCHEMY_TOKEN}`,
+        blockNumber: 14000000,
+      }
+    }
+  },
+  mocha: {
+    timeout: 100000
+  },
+  logger: process.env.SILENT ? { log: () => {} } : console,
+};

test/integration/projects/hardhat-reset/test/testReset.js

@@ -0,0 +1,43 @@
+const { expect } = require("chai");
+const { ethers } = require("hardhat");
+
+describe("contractA", function() {
+  let instance;
+  let startBlockNumber;
+
+  beforeEach(async () => {
+    startBlockNumber = await ethers.provider.getBlockNumber();
+
+    await hre.network.provider.request({
+        method: "hardhat_reset",
+        params: [
+          {
+            forking: {
+              jsonRpcUrl: `https://eth-mainnet.alchemyapi.io/v2/${process.env.ALCHEMY_TOKEN}`,
+              blockNumber: startBlockNumber,
+            },
+          },
+        ],
+      });
+
+    const factory = await ethers.getContractFactory("ContractA");
+    instance = await factory.deploy();
+  });
+
+  it('sends', async function(){
+    await instance.sendFn();
+  });
+
+  it('sends 2', async function(){
+    await instance.sendFn2();
+  });
+
+  it('calls', async function(){
+    await instance.callFn();
+  });
+
+  it('calls 2', async function(){
+    await instance.callFn2();
+  });
+});
+

test/units/hardhat/standard.js

@@ -342,6 +342,22 @@ describe('Hardhat Plugin: standard use cases', function() {
     verify.lineCoverage(expectedLine);
   });
 
+  it('hardhat_reset preserves coverage between resets', async function(){
+    mock.installFullProject('hardhat-reset');
+    mock.hardhatSetupEnv(this);
+
+    await this.env.run("coverage");
+
+    const expected = [
+      {
+        file: mock.pathToContract(hardhatConfig, 'ContractAReset.sol'),
+        pct: 100
+      }
+    ];
+
+    verify.lineCoverage(expected);
+  })
+
   // This test freezes when gas-reporter is not disabled
   it('disables hardhat-gas-reporter', async function() {
     mock.installFullProject('hardhat-gas-reporter');