function getNextNonce in provider

src/Provider.ts

@@ -9,7 +9,7 @@ import {
 // eslint-disable-next-line @typescript-eslint/ban-ts-comment
 // @ts-ignore
 import { koinos } from "./protoModules/protocol-proto.js";
-import { decodeBase64url } from "./utils";
+import { decodeBase64url, encodeBase64url } from "./utils";
 
 /* eslint-disable @typescript-eslint/no-unsafe-call, @typescript-eslint/no-unsafe-assignment, @typescript-eslint/no-unsafe-member-access */
 
@@ -140,8 +140,8 @@ export class Provider {
 
   /**
    * Function to call "chain.get_account_nonce" to return the number of
-   * transactions for a particular account. This call is used
-   * when creating new transactions.
+   * transactions for a particular account. If you are creating a new
+   * transaction consider using [[Provider.getNextNonce]].
    * @param account - account address
    * @param deserialize - If set true it will deserialize the nonce
    * and return it as number (default). If set false it will return
@@ -171,6 +171,27 @@ export class Provider {
     return Number(object.uint64_value);
   }
 
+  /**
+   * Function to call "chain.get_account_nonce" (number of
+   * transactions for a particular account) and return the next nonce.
+   * This call is used when creating new transactions. The result is
+   * encoded in base64url
+   * @param account - account address
+   * @returns Nonce
+   */
+  async getNextNonce(account: string): Promise<string> {
+    const oldNonce = (await this.getNonce(account)) as number;
+    const message = koinos.chain.value_type.create({
+      // todo: consider using bigint for big nonces
+      uint64_value: String(oldNonce + 1),
+    });
+    const nonceEncoded = koinos.chain.value_type
+      .encode(message)
+      .finish() as Uint8Array;
+
+    return encodeBase64url(nonceEncoded);
+  }
+
   async getAccountRc(account: string): Promise<string> {
     const { rc } = await this.call<{ rc: string }>("chain.get_account_rc", {
       account,

src/Signer.ts

@@ -654,16 +654,7 @@ export class Signer implements SignerInterface {
         throw new Error(
           "Cannot get the nonce because provider is undefined. To skip this call set a nonce in the transaction header"
         );
-      const oldNonce = (await this.provider.getNonce(payee || payer)) as number;
-      const message = koinos.chain.value_type.create({
-        // todo: consider using bigint for big nonces
-        uint64_value: String(oldNonce + 1),
-      });
-      const nonceEncoded = koinos.chain.value_type
-        .encode(message)
-        .finish() as Uint8Array;
-
-      nonce = encodeBase64url(nonceEncoded);
+      nonce = await this.provider.getNextNonce(payee || payer);
     } else {
       nonce = tx.header.nonce;
     }

tests/wallet.spec.ts

@@ -1214,6 +1214,19 @@ describe("Wallet and Contract", () => {
     expect(transaction!.header!.payer).toBe(signer2.getAddress());
   });
 
+  it("should get nonce and next nonce", async () => {
+    const myProvider = new Provider(["http://good-server"]);
+    mockFetch.mockImplementation(async () => {
+      return fetchResponse({ nonce: "KAA=" });
+    });
+    const nonce = await myProvider.getNonce(address);
+    const nonceBase64url = await myProvider.getNonce(address, false);
+    const nextNonceBase64url = await myProvider.getNextNonce(address);
+    expect(nonce).toBe(0);
+    expect(nonceBase64url).toBe("KAA=");
+    expect(nextNonceBase64url).toBe("KAE=");
+  });
+
   it("should change node", async () => {
     expect.assertions(2);
     const myProvider = new Provider([