Using web3 v1 beta from Nodejs to invoke myMethod.send() gives use Trusted Signer. How do I do that?

Question

Using web3 version 1 beta 27, connected to a remote Parity node that's connected to the Ropsten network.

I have created an account with public and private keys, I have sent some test Eth to that address. That all works fine.

Now trying to actually invoke a function on my contract I get the message

Your account is locked. Unlock the account via CLI, personal_unlockAccount or use Trusted Signer

I don't have access to the node via CLI so need to use Trusted Signer.

Looking at the docs for web3.eth.accounts.sign I see the following

sign

web3.eth.accounts.sign(data, privateKey);

Signs arbitrary data. This data is before UTF-8 HEX decoded and enveloped as follows: "\x19Ethereum Signed Message:\n" + message.length + message.

Parameters

1. data - String: The data to sign. If its a string it will be
2. privateKey - String: The private key to sign with.

which quite frankly doesn't make any sense.

Assuming the function I am calling is

TestContract.methods.test(testAddress).send()

How exactly do I use web3.eth.accounts.sign in this context?

Answer 1

I've worked this out now. First up I need to ensure I have access to the private key for the address, as well as the sender's address.

Given that information I can do the following.

const testFn = TestContract.methods.test(testAddress)
const gas = await testFn.estimateGas()
const account = web3.eth.accounts.privateKeyToAccount(PRIVATE_KEY)
const data = testFn.encodeABI()
const nonce = await web3.eth.getTransactionCount(SENDER_ADDRESS, 'pending')
const payload = {
  nonce,
  data,
  gas,
  from: SENDER_ADDRESS,
  to: testContractAddress
}
const signedTx = await account.signTransaction(payload, account.privateKey)
const { rawTransaction } = signedTx
const response = await web3.eth.sendSignedTransaction(rawTransaction)

This works fine.

Obviously this is only suitable for code running in NodeJS as you never want the private key to be exposed in a public web interface.