Sub-Calls via Catalyst

The default output type of Catalyst, called OutputDescription, supports secondary calls. This allows you to schedule calldata to be executed after the delivery of the asset.

Outputs are filled unorderly

Outputs are filled unorderly. As a result, if you want to receive both Ether and USDC to your destination contract and then execute a call using both Ether and USDC, this may not be possible. This is because either USDC or Ether may arrive before the other, and as a result, the logic may not execute correctly.

Natively, Catalyst will deliver the output of OutputDescription and then call the destination.

/**
 * @notice Implement callback handling for Cross cats payouts, both outputs and inputs.
 * @dev Callbacks are opt-in. If you opt-in, take care not to revert.
 * Funds are likely in danger if the calls revert. Please be careful.
 *
 * If you don't need this functionality, stay away.
 *
 * The recipient is called.
 */
interface ICrossCatsCallback {
    /**
     * @dev If the transaction reverts, 1 million gas is provided.
     * If the transaction doesn't revert, only enough gas to execute the transaction is given, plus a buffer of 1/63'th.
     * The recipient is called.
     * If the call reverts, funds are still delivered to the recipient.
     * Please ensure that funds are safely handled on your side.
     */
    function outputFilled(bytes32 token, uint256 amount, bytes calldata executionData) external;

    /**
     * @notice If configured, is called when the input is sent to the filler.
     */
    function inputsFilled(uint256[2][] calldata inputs, bytes calldata executionData) external;
}

Additionally, Catalyst provides a multicall handler with the following defined structs:

struct Call {
    address target;
    bytes callData;
    uint256 value;
}

struct Instructions {
    // If set to an address (not address(0)), then the tokens sent to this contract on the call
    // will be approved for this address.
    address setApprovalsUsingInputsFor;
    // Calls that will be attempted.
    Call[] calls;
    // Where the tokens go if any part of the call fails.
    // Leftover tokens are sent here as well if the action succeeds.
    address fallbackRecipient;
}

When used: set remoteCall = abi.encode(Instructions).

For the default Catalyst OutputDescription:

struct OutputDescription {
    bytes32 remoteOracle;
    bytes32 remoteFiller;
    uint256 chainId;
    bytes32 token;
    uint256 amount;
    bytes32 recipient; // = addressOf(CatsMulticallHandler)
    bytes remoteCall; // = abi.encode(Instructions)
    bytes fulfillmentContext;
}