web3.js: add accounts support to simulateTransaction (#19590)

* feat: add accounts support to simulateTransaction

* feat: introduce test for simulateTransaction on Message objects

* feat: populate transaction from message defaults to no signatures

* fix: remove unused constant

* fix: small formatting error

* fix: eslint and prettier were fighting over ternary indentation

* fix: make simulated transaction result accounts nullable

web3.js/test/connection.test.ts

@@ -17,6 +17,7 @@ import {
   StakeProgram,
   sendAndConfirmTransaction,
   Keypair,
+  Message,
 } from '../src';
 import invariant from '../src/util/assert';
 import {DEFAULT_TICKS_PER_SLOT, NUM_TICKS_PER_SECOND} from '../src/timing';
@@ -2818,6 +2819,65 @@ describe('Connection', () => {
   });
 
   if (process.env.TEST_LIVE) {
+    it('simulate transaction with message', async () => {
+      connection._commitment = 'confirmed';
+
+      const account1 = Keypair.generate();
+      const account2 = Keypair.generate();
+
+      await helpers.airdrop({
+        connection,
+        address: account1.publicKey,
+        amount: LAMPORTS_PER_SOL,
+      });
+
+      await helpers.airdrop({
+        connection,
+        address: account2.publicKey,
+        amount: LAMPORTS_PER_SOL,
+      });
+
+      const recentBlockhash = await (
+        await helpers.recentBlockhash({connection})
+      ).blockhash;
+      const message = new Message({
+        accountKeys: [
+          account1.publicKey.toString(),
+          account2.publicKey.toString(),
+          'Memo1UhkJRfHyvLMcVucJwxXeuD728EqVDDwQDxFMNo',
+        ],
+        header: {
+          numReadonlySignedAccounts: 1,
+          numReadonlyUnsignedAccounts: 2,
+          numRequiredSignatures: 1,
+        },
+        instructions: [
+          {
+            accounts: [0, 1],
+            data: bs58.encode(Buffer.alloc(5).fill(9)),
+            programIdIndex: 2,
+          },
+        ],
+        recentBlockhash,
+      });
+
+      const results1 = await connection.simulateTransaction(
+        message,
+        [account1],
+        true,
+      );
+
+      expect(results1.value.accounts).lengthOf(2);
+
+      const results2 = await connection.simulateTransaction(
+        message,
+        [account1],
+        [account1.publicKey],
+      );
+
+      expect(results2.value.accounts).lengthOf(1);
+    }).timeout(10000);
+
     it('transaction', async () => {
       connection._commitment = 'confirmed';