support newer versons of ethereumjs/tx with immutability

index.js

@@ -51,8 +51,9 @@ class SimpleKeyring extends EventEmitter {
   // tx is an instance of the ethereumjs-transaction class.
   signTransaction (address, tx, opts = {}) {
     const privKey = this.getPrivateKeyFor(address, opts)
-    tx.sign(privKey)
-    return Promise.resolve(tx)
+    const signedTx = tx.sign(privKey)
+    // Newer versions of Ethereumjs-tx are immutable and return a new tx object
+    return Promise.resolve(signedTx === undefined ? tx : signedTx)
   }
 
   // For eth_sign, we need to sign arbitrary data:

package.json

@@ -32,6 +32,7 @@
     "events": "^1.1.1"
   },
   "devDependencies": {
+    "@ethereumjs/tx": "^3.1.1",
     "@metamask/eslint-config": "^3.2.0",
     "chai": "^4.1.2",
     "eslint": "^7.2.0",

test/index.js

@@ -4,6 +4,7 @@ const assert = require('assert')
 const ethUtil = require('ethereumjs-util')
 const sigUtil = require('eth-sig-util')
 const { Transaction: EthereumTx } = require('ethereumjs-tx')
+const { TransactionFactory } = require('@ethereumjs/tx')
 const { expect } = require('chai')
 const SimpleKeyring = require('..')
 
@@ -82,6 +83,23 @@ describe('simple-keyring', () => {
       const signed = await keyring.signTransaction(address, tx)
       assert.ok(signed.raw, 'has a raw signature')
     })
+
+    it('returns a signed tx object when using newer versions of ethereumjs/tx', async () => {
+      await keyring.deserialize([privateKey])
+
+      const txParams = {
+        from: address,
+        nonce: '0x00',
+        gasPrice: '0x09184e72a000',
+        gasLimit: '0x2710',
+        to: address,
+        value: '0x1000',
+      }
+      const tx = TransactionFactory.fromTxData(txParams)
+
+      const signed = await keyring.signTransaction(address, tx)
+      assert.ok(signed.raw, 'has a raw signature')
+    })
   })
 
   describe('#signMessage', () => {