Using a `SignerWithAddress` to sign a transaction from `populateTransaction` fails with "Signing transactions is unsupported"

Describe the bug

I am creating an unsigned transaction with contractMethod.populateTransaction.method() then signing with signer.SignTransaction(unsignedTransaction)

The second step fails with

  reason: 'signing transactions is unsupported',
  code: 'UNSUPPORTED_OPERATION',
  operation: 'signTransaction'

Reproduction steps

  const MyContract = await ethers.getContractFactory('MyContract')
  const signers = await ethers.getSigners()
  const admin = signers[0]
  

  
  const myContract = (await MyContract.attach(myContractAddress)) as MyContract
  
  const unlockTransaction = await myContract.populateTransaction.testMethod(true, {nonce: firstNonce})
  const unlockTransactionSigned = await admin.signTransaction(unlockTransaction)

Environment: Node v14 Goerli

Search Terms Ethers Sign raw transaction

[ricmoo]

Correct. It exists because it sub-classes Signer, but if the client doesn’t support it, it will throw an error when it is attempted to be used.

[ricmoo]

That is a JsonRpcSigner instance, not a Wallet instance. So it depends on what Provider you are using, but most providers you need a Web3Provider for will not support signing a transaction as it is a security and UX concern. That’s nothing to do with ethers, that is the client deciding to not allowing signing transactions (for good reasons).