add network id to autofill

packages/xrpl/src/sugar/autofill.ts

@@ -9,6 +9,7 @@ import { setTransactionFlagsToNumber } from '../models/utils/flags'
 import { xrpToDrops } from '../utils'
 
 import getFeeXrp from './getFeeXrp'
+import getNetworkID from './getNetworkID'
 
 // Expire unconfirmed transactions after 20 ledger versions, approximately 1 minute, by default
 const LEDGER_OFFSET = 20
@@ -39,8 +40,10 @@ async function autofill<T extends Transaction>(
   setValidAddresses(tx)
 
   setTransactionFlagsToNumber(tx)
-
   const promises: Array<Promise<void>> = []
+  if (tx.NetworkID == null) {
+    promises.push(setNetworkID(this, tx))
+  }
   if (tx.Sequence == null) {
     promises.push(setNextValidSequenceNumber(this, tx))
   }
@@ -200,6 +203,12 @@ function scaleValue(value, multiplier): string {
   return new BigNumber(value).times(multiplier).toString()
 }
 
+async function setNetworkID(client: Client, tx: Transaction): Promise<void> {
+  const id = await getNetworkID(client)
+  // eslint-disable-next-line no-param-reassign -- param reassign is safe
+  tx.NetworkID = id
+}
+
 async function setLatestValidatedLedgerSequence(
   client: Client,
   tx: Transaction,

packages/xrpl/src/sugar/getNetworkID.ts

@@ -0,0 +1,22 @@
+import type { Client } from '..'
+import { XrplError } from '../errors'
+
+/**
+ * Returns the network ID of the rippled server.
+ *
+ * @param this - The Client used to connect to the ledger.
+ * @param client
+ * @returns The network id.
+ */
+export default async function getNetworkID(client: Client): Promise<number> {
+  const response = await client.request({
+    command: 'server_info',
+  })
+  const networkID = response.result.info.network_id
+  if (networkID == null) {
+    throw new XrplError(
+      'getNetworkID: Could not get network_id from server_info',
+    )
+  }
+  return networkID
+}