Function getRequestedDirection

lib/stdio/direction.js:29–36

({type, value, direction, optionName})

// The explicitly requested `direction` must not contradict a value that is intrinsically the other direction.
// For example, `{value: writableStream, input: true}` is invalid since a writable value can only be an output.
const getRequestedDirection = ({type, value, direction, optionName}) => {
	const guessedDirection = guessStreamDirection[type](value);
	if (direction === 'input' && guessedDirection === 'output') {
		throw new TypeError(`The \`${optionName}\` option is invalid: \`input: true\` cannot be used with a writable value, which is always an output.`);
	}

	return direction ?? guessedDirection;
};

// `stdin`/`stdout`/`stderr` have a known direction
const KNOWN_DIRECTIONS = ['input', 'output', 'output'];