How can I overwrite all trustline flags?

Question

I'm trying to overwrite the current trustline flags, but I have issues with that. I keep getting setTrustLineFlagsMalformed, but I don't know why.

Am I using this function wrong?

tx.append_set_trust_line_flags_op(
    trustor=trustor.public_key,
    asset=asset,
    set_flags=TrustLineFlags.AUTHORIZED_TO_MAINTAIN_LIABILITIES_FLAG,
)

MCVE: Minimal complete verifiable example

from stellar_sdk import (
    Asset,
    TransactionBuilder,
    Keypair,
    Network,
    Server,
    TrustLineFlags,
)


def play_with_trust(trustor: Keypair, asset: Asset):
    source_account = server.load_account(trustor.public_key)
    tx = TransactionBuilder(
        source_account=source_account,
        network_passphrase=Network.TESTNET_NETWORK_PASSPHRASE,
        base_fee=100,
    )
    # tx = tx.append_change_trust_op(
    #             asset=asset
    #         )
    tx.append_set_trust_line_flags_op(
        trustor=trustor.public_key,
        asset=asset,
        set_flags=TrustLineFlags.AUTHORIZED_TO_MAINTAIN_LIABILITIES_FLAG,
    )
    tx = tx.set_timeout(300)
    tx_envelope = tx.build()
    tx_envelope.sign(trustor)
    return server.submit_transaction(tx_envelope)


if __name__ == "__main__":
    is_initial = False
    server = Server(horizon_url="https://horizon-testnet.stellar.org")
    secrets = [
        "SCFRDE3BMOF67LC254SLC4NMBYCDA4MRVGLAKVARC24TGGF4LJCZJKZF",
        "SDD6AFQ5JIP7EXZNFZSLEY5AEIOPNVI35WVNDVC22AWW7RAIW4RQZPH4",
        "SACID3EGZHQLZWHYOK6L2RJNMOQHTJIUG6NOLCRMTXTC5CA7DEYBWQA3",
        "SB6MJ6M3BPJZUGFP2QCODUIKWQWF6AIN4Z6L3J6PWL3QGDW4L6YR3QIU",
    ]
    trustor = Keypair.from_secret(secrets[0])
    destination = Keypair.from_secret(secrets[1])
    issuing_keypair = Keypair.from_secret(secrets[2])
    distributor_keypair = Keypair.from_secret(secrets[3])
    print(f"trustor: http://testnet.stellarchain.io/address/{trustor.public_key}")
    asset = Asset("BSS", issuing_keypair.public_key)

    result = play_with_trust(trustor, asset)
    print(result)

Answer 1

I found the issue in the docs (sadly the link seems not to work ... search for "setTrustlineFlags"):

This can happen for a number of reasons: the asset specified by AssetCode and AssetIssuer is invalid; the asset issuer isn’t the source account; the Trustor is the source account; the native asset is specified; or the flags being set/cleared conflict or are otherwise invalid

So four potential reasons:

1. the asset specified by AssetCode and AssetIssuer is invalid
2. the asset issuer isn’t the source account => This was an issue
3. Trustor is the source account => This was an issue
4. the flags being set/cleared conflict or are otherwise invalid

The "source account" refers to the parameter of the TransactionBuilder. You can specify a source account for append_set_trust_line_flags_op as well.