How to convert a MessageCompiledInstruction to TransactionInstruction in web3.js

Question

I have a VersionedTransaction, which has a message with some instructions of type MessageCompiledInstruction. I'm trying to decode the ComputeBudgetInstruction with the following code:

const msg = versionedTransaction.message
for (const ix of msg.compiledInstructions) {
    if (msg.staticAccountKeys[ix.programIdIndex].toBase58() == "ComputeBudget111111111111111111111111111111") {
    console.log(ix)
// e.g.
//{
//  programIdIndex: 19,
//  accountKeyIndexes: [],
//  data: <Buffer 02 ae 02 04 00>
//}

    ComputeBudgetInstruction.decodeInstructionType(ix)
  }
}

I want to decode the compute budget instructions, however decodeInstructionType takes in input a TransactionInstruction, which can be instantiated with the following constructor:

  type TransactionInstructionCtorFields = {
    keys: Array<AccountMeta>;
    programId: PublicKey;
    data?: Buffer;
  };

I'm not sure where to get the AccountMeta objects. So in short my question is how to convert a MessageCompiledInstruction to TransactionInstruction?

Answer 1

If you have a versioned transaction, you can get the instructions of that transaction by

    let ixs = TransactionMessage.decompile(
        versionedTx.message
    ).instructions;

The AccountMeta struct is used to declare the accounts the instruction reads and writes to.

Here's an example pulled from the docs with the transfer sol instruction

const transferInstruction = new TransactionInstruction({
  keys: [
    { pubkey: sender.publicKey, isSigner: true, isWritable: true },
    { pubkey: receiver.publicKey, isSigner: false, isWritable: true },
  ],
  programId: SystemProgram.programId,
  data: instructionData,
});

AccountMeta ref: https://solana.com/docs/core/transactions#accountmeta

Ideally, you wouldn't be writing every transaction instruction account as most programs on Solana build the tx for you, e.g the transfer

const transferInstruction = SystemProgram.transfer({
  fromPubkey: sender.publicKey,
  toPubkey: receiver.publicKey,
  lamports: transferAmount * LAMPORTS_PER_SOL, // Convert transferAmount to lamports
});

In your example, you can request more compute units for a program using

const modifyComputeUnits = ComputeBudgetProgram.setComputeUnitLimit({
  units: 300_000,
});