Remove hardcoding of localhost to use server assigned loopback and port

Update to handle 127.0.0.1 instead of localhost.

squash

README.md

@@ -588,6 +588,8 @@ return Functions.encodeString(escape("$hello*world?"));
 **_NOTE:_** The `simulateScript` function is a debugging tool and hence is not a perfect representation of the actual Chainlink oracle execution environment. Therefore, it is important to make a Functions request on a supported testnet blockchain before mainnet usage.
 
 ### Local Functions Testnet
+> **Note**
+> Anvil is required to use `localFunctionsTestnet`. Please refer to the [foundry book](https://book.getfoundry.sh) for Anvil [installation instructions](https://book.getfoundry.sh/getting-started/installation).
 
 For debugging smart contracts and the end-to-end request flow on your local machine, you can use the `localFunctionsTestnet` function. This creates a local testnet RPC node with a mock Chainlink Functions contracts. You can then deploy your own Functions consumer contract to this local network, create and manage subscriptions, and send requests. Request processing will simulate the behavior of an actual DON where the request is executed 4 times and the discrete median response is transmitted back to the consumer contract. (Note that Chainlink Functions uses the following calculation to select the discrete median response: `const medianResponse = responses[responses.length - 1) / 2]`).
 
@@ -596,11 +598,12 @@ The `localFunctionsTestnet` function takes the following values as arguments.
 ```
 const localFunctionsTestnet = await startLocalFunctionsTestnet(
   simulationConfigPath?: string // Absolute path to config file which exports simulation config parameters
-  options?: ServerOptions, // Ganache server options
-  port?: number, // Defaults to 8545
+  options?: ServerOptions, // Anvil server options (See: https://www.npmjs.com/package/@viem/anvil#api and https://book.getfoundry.sh/reference/anvil/)
 )
 ```
 
+`ServerOptions` is optional, and ships with a default `port` of 8545 and the default `test test test...junk`  BIP39 mnemonic.  
+
 Observe that `localFunctionsTestnet` takes in a `simulationConfigPath` string as an optional argument. The primary reason for this is because the local testnet does not have the ability to access or decrypt encrypted secrets provided within request transactions. Instead, you can export an object named `secrets` from a TypeScript or JavaScript file and provide the absolute path to that file as the `simulationConfigPath` argument. When the JavaScript code is executed during the request, secrets specified in that file will be made accessible within the JavaScript code regardless of the `secretsLocation` or `encryptedSecretsReference` values sent in the request transaction. This config file can also contain other simulation config parameters. An example of this config file is shown below.
 
 ```
@@ -619,7 +622,7 @@ export const maxQueryResponseBytes = 2097152 // Maximum size of incoming HTTP re
 
 ```
 {
-  server: Server // Ganache server
+  server: Server // Anvil server
   adminWallet: { address: string, privateKey: string } // Funded admin wallet
   getFunds: (address: string, { weiAmount, juelsAmount }: { weiAmount?: BigInt | string; juelsAmount?: BigInt | string }) => Promise<void> // Method which can be called to send funds to any address
   close: () => Promise<void> // Method to close the server

package.json

@@ -78,6 +78,7 @@
     "eth-crypto": "^2.6.0",
     "ethers": "^5.7.2",
     "ganache": "^7.9.1",
-    "uniq": "^1.0.1"
+    "uniq": "^1.0.1",
+    "@viem/anvil": "^0.0.7"
   }
-}
+}

src/localFunctionsTestnet.ts

@@ -1,5 +1,6 @@
-import { Wallet, Contract, ContractFactory, utils, providers } from 'ethers'
-import Ganache from 'ganache'
+import { ethers, Wallet, Contract, ContractFactory, utils } from 'ethers'
+import { createAnvil } from '@viem/anvil'
+import type { Anvil, CreateAnvilOptions } from '@viem/anvil'
 import cbor from 'cbor'
 
 import { simulateScript } from './simulateScript'
@@ -23,8 +24,6 @@ import {
   TermsOfServiceAllowListSource,
 } from './v1_contract_sources'
 
-import type { ServerOptions } from 'ganache'
-
 import type {
   FunctionsRequestParams,
   RequestCommitment,
@@ -36,27 +35,35 @@ import type {
 
 export const startLocalFunctionsTestnet = async (
   simulationConfigPath?: string,
-  options?: ServerOptions,
+  options?: CreateAnvilOptions,
   port = 8545,
 ): Promise<LocalFunctionsTestnet> => {
-  const server = Ganache.server(options)
+  let localhost: string
+  let anvilNode: Anvil
 
-  server.listen(port, 'localhost', (err: Error | null) => {
-    if (err) {
-      throw Error(`Error starting local Functions testnet server:\n${err}`)
-    }
-    console.log(`Local Functions testnet server started on port ${port}`)
-  })
+  const junkMnemonic = 'test test test test test test test test test test test junk'
 
-  const accounts = server.provider.getInitialAccounts()
-  const firstAccount = Object.keys(accounts)[0]
-  const admin = new Wallet(
-    accounts[firstAccount].secretKey.slice(2),
-    new providers.JsonRpcProvider(`http://localhost:${port}`),
-  )
+  const anvilOpts = {
+    port,
+    mnemonic: junkMnemonic,
+    ...options,
+  }
 
-  const contracts = await deployFunctionsOracle(admin)
+  try {
+    anvilNode = createAnvil(anvilOpts)
+    await anvilNode.start()
+    localhost = `http://${anvilNode.host}:${anvilNode.port}`
+    console.log(`Local Functions testnet server ${anvilNode.status} at ${localhost}...`)
+  } catch (error) {
+    throw Error(`Error starting local Functions testnet server:\n${error}`)
+  }
 
+  const provider = new ethers.providers.JsonRpcProvider(localhost)
+  let admin = Wallet.fromMnemonic(junkMnemonic)
+  console.info('Using admin wallet address: ', admin.address)
+  admin = admin.connect(provider)
+
+  const contracts = await deployFunctionsOracle(admin)
   contracts.functionsMockCoordinatorContract.on(
     'OracleRequest',
     (
@@ -123,11 +130,11 @@ export const startLocalFunctionsTestnet = async (
 
   const close = async (): Promise<void> => {
     contracts.functionsMockCoordinatorContract.removeAllListeners('OracleRequest')
-    await server.close()
+    await anvilNode.stop()
   }
 
   return {
-    server,
+    server: anvilNode,
     adminWallet: {
       address: admin.address,
       privateKey: admin.privateKey,