TypeError: Expected Buffer when sending transactions with complex account structures

[decider]

(Made by Claude Code, reviewed by @decider)

Title: TypeError: Expected Buffer when sending transactions with complex account structures

Repository: LiteSVM/anchor-litesvm

Issue Description:

When using anchor-litesvm v0.1.2 to test Solana programs, certain transactions fail with TypeError: Expected Buffer during the base58 encoding phase. This occurs specifically with transactions that involve complex account structures or multiple signers.

Environment:

• anchor-litesvm: 0.1.2
• @coral-xyz/anchor: 0.31.1
• @solana/web3.js: 1.98.2

Error Stack Trace:

TypeError: Expected Buffer
    at Object.encode (node_modules/anchor-litesvm/node_modules/base-x/src/index.js:27:44)
    at sendWithErr (node_modules/anchor-litesvm/src/index.ts:74:26)
    at LiteSVMProvider.sendAndConfirm (node_modules/anchor-litesvm/src/index.ts:150:3)
    at MethodsBuilder.rpc [as _rpcFn] (client/node_modules/@coral-xyz/anchor/src/program/namespace/rpc.ts:29:31)
    at MethodsBuilder.rpc (client/node_modules/@coral-xyz/anchor/src/program/namespace/methods.ts:434:17)

Reproduction Steps:

1. Create a test that initializes extra account meta list and adds a region:

import { LiteSVMProvider, fromWorkspace } from "anchor-litesvm";
import * as anchor from "@coral-xyz/anchor";

const client = fromWorkspace(".");
const provider = new LiteSVMProvider(client, new anchor.Wallet(adminWallet));

// This transaction fails with "Expected Buffer" error
await program.methods
  .addRegion({ name: "Test Region", symbol: "TEST", uri: "https://test.com" })
  .accounts({
    admin: adminWallet.publicKey,
    tokenVault: accounts.tokenVault,
    platformState: accounts.platformState,
    regionState: accounts.regionState,
    usdcYieldPool: accounts.usdcYieldPool,
    feeTokenPool: accounts.feeTokenPool,
    mint: accounts.regionalMint.publicKey,
    usdcMint: accounts.usdcMint,
    tokenProgram: TOKEN_PROGRAM_ID,
    token2022Program: TOKEN_2022_PROGRAM_ID,
    associatedTokenProgram: anchor.utils.token.ASSOCIATED_PROGRAM_ID,
    systemProgram: SystemProgram.programId,
    rent: SYSVAR_RENT_PUBKEY,
  })
  .signers([accounts.regionalMint, adminWallet])
  .rpc();

2. Similar error occurs with pool registry transactions:

await program.methods
  .registerPool(poolAddress, dexProgram, poolType)
  .accounts({
    admin: adminWallet.publicKey,
    poolRegistry,
    regionMint,
    platformState: context.pdas.platformState,
    systemProgram: anchor.web3.SystemProgram.programId,
  })
  .rpc();

Expected Behavior:

Transactions should be properly encoded and sent to the LiteSVM instance without encoding errors.

Actual Behavior:

The transaction fails during base58 encoding with "TypeError: Expected Buffer" before reaching the LiteSVM instance.

Analysis:

The error occurs in the sendWithErr function at line 74 of anchor-litesvm's index.ts, specifically during the base58 encoding of the transaction signature. This suggests that the signature might not be in the expected format (Buffer) when it reaches the encoding step.

Workaround:

Currently, we have to skip tests that trigger this error. Simple transactions (like basic initialization) work fine, but more complex transactions with multiple accounts or signers fail.

Impact:

This issue prevents testing of complex Solana program interactions with anchor-litesvm, limiting its usefulness for comprehensive test suites. We can only test simple transactions while more complex scenarios fail.

Additional Context:

• The same transactions work correctly with standard Anchor testing using solana-test-validator
• The issue appears to be specific to how anchor-litesvm handles transaction encoding
• Tests for simpler operations (platform initialization, balance checks) work perfectly

Possible Solutions:

1. Ensure transaction signatures are properly converted to Buffer format before base58 encoding
2. Update the signature handling in the sendWithErr function
3. Add better type checking/conversion for transaction data before encoding

Would love to help test any fixes or provide more details if needed!

[Bogdan-Decu]

Same situation here. The problem is incompatibility with latest anchor versions. Is someone working on this?