Function getStreamDirection

lib/stdio/direction.js:13–21

(stdioItems, fdNumber, optionName)

// When `stdio[fdNumber]` is a single value, this guess is fairly straightforward.
// However, when it is an array instead, we also need to make sure the different values are not incompatible with each other.
export const getStreamDirection = (stdioItems, fdNumber, optionName) => {
	const directions = stdioItems.map(stdioItem => getStdioItemDirection(stdioItem, fdNumber));

	if (directions.includes('input') && directions.includes('output')) {
		throw new TypeError(`The \`${optionName}\` option must not be an array of both readable and writable values.`);
	}

	return directions.find(Boolean) ?? DEFAULT_DIRECTION;
};

// `direction` is set when the user explicitly requests it, e.g. `{value: 'pipe', input: true}`.
// It takes precedence over guessing, but not over the fixed direction of `stdin`/`stdout`/`stderr`.