I'm facing custom program error: 0x0 when try to derivated a PDA with custom seeds

Question

I'm facing an issue in my instruction trying to generate a PDA from a string and user.key(), just like in the PDA Anchor tutorial. I tried it in various ways and still, I get the same error: Error: failed to send transaction: Transaction simulation failed: Error processing Instruction 0: custom program error: 0x0

This is my instruction:

#[derive(Accounts)]

pub struct CreateCollection<'info> {
    #[account(
        init, 
        payer=user, 
        space = 8 + 32 + 1,
        seeds = [b"user-collection", user.key().as_ref()],
        bump
    )]
    pub collection: Account<'info, Collection>,
    #[account(mut)]
    pub user: Signer<'info>,
    pub system_program: Program<'info, System>,
}

pub fn handler(
    ctx: Context<CreateCollection>, 
) -> Result<()> {

    let collection = &mut ctx.accounts.collection;
    let user = &ctx.accounts.user;
    
    collection.user = *user.key;
    collection.bump = *ctx.bumps.get("collection").unwrap();

    Ok(())

}

#[account]
pub struct Collection {
    pub user: Pubkey, 
    pub bump: u8,  
}

And this is my test:

it("Can create a Collection", async () => {
    
    const [collectionPublicKey, _] = web3.PublicKey.findProgramAddressSync(
      [Buffer.from("user-collection"), anchorProvider.wallet.publicKey.toBuffer()],
      program.programId,
    )

    
    await program.methods
    .createCollection()
    .accounts({
        collection: collectionPublicKey,
        user: anchorProvider.wallet.publicKey,
        systemProgram: web3.SystemProgram.programId,
    })
    .rpc()

    let account = await program.account.collection.fetch(collectionPublicKey)
    console.log(JSON.stringify(account, null, 2))
    console.log(collectionPublicKey)
  });

Answer 1

Are you running the test on devnet? If so, the error you're encountering could be due to the account having been initialized previously. Since you're using the wallet pubkey as one of the seeds, it means each wallet can only create one Collection account from your program. If the same wallet invokes the instruction again, then the transaction will fail because the account already exists.

You can try updating Anchor.toml and then run anchor test on localnet:

[programs.localnet]
...

[provider]
cluster = "localnet"