Preconditions

Preconditions are modules that contains logics that are used to check if a command can be executed.

You can create a precondition by creating a module that extends the built-in precondition module PreconditionModule

Structure

import { PreconditionModule } from "reciple";

class MyPrecondition extends PreconditionModule {
    async execute(data) {
        return true;
    }
}

export default MyPrecondition;

A precondition must implement the abstract method execute(). The method must return a value whether the command can be executed or not.

Return Values

• true — The command precondition succeeded and the command can be executed.
• false — The command precondition failed and the command cannot be executed.
• string — The command precondition failed and the command cannot be executed. The given string will be used as reason message (Not an error).
• Error — The command precondition failed with an error and the command cannot be executed.
• CommandPrecondition.ResultData — The full result data of the command precondition.

Failed vs Error

A precondition fail and error are different.

Failed

A failed precondition is identified when the precondition’s execute() method returns false, string, or result data with a success property set to false.

If the value returned is false or string values, it will be coerced to a result data with a success property set to false and the given string as message.

When a precondition fails, the command will not be executed. However, the command’s postconditions will still be executed.

A precondition can assign a specific postcondition to be executed when the precondition fails by defining .postconditionExecute property of the result data.

Error

A precondition error is identified when a precondition returns a result data with a success property set to false and error property is defined. It is also possible to return or throw an error from a precondition to indicate an error.

If the precondition throws or returns an error, it will be coerced to a result data with a success property set to false and the error assigned to the error property.

The postconditions will still be executed. However, the error will be thrown when these postconditions doesn’t handle the error.

Execution

All precondition are executed first before the command executes, then each result data of each precondition are stored in a PreconditionResultManager. The precondition result manager is then used to determine whether the preconditions has an error or failed.