astro/dist/core/app/createOutgoingHttpHeaders.js

Astro is a modern site builder with web best practices, performance, and DX front-of-mind.

/**
* Takes in a nullable WebAPI Headers object and produces a NodeJS OutgoingHttpHeaders object suitable for usage
* with ServerResponse.writeHead(..) or ServerResponse.setHeader(..)
*
* @param headers WebAPI Headers object
* @returns {OutgoingHttpHeaders} NodeJS OutgoingHttpHeaders object with multiple set-cookie handled as an array of values
*/
export const createOutgoingHttpHeaders = (headers) => {
	if (!headers) {
		return undefined;
	}
	// at this point, a multi-value'd set-cookie header is invalid (it was concatenated as a single CSV, which is not valid for set-cookie)
	const nodeHeaders = Object.fromEntries(headers.entries());
	if (Object.keys(nodeHeaders).length === 0) {
		return undefined;
	}
	// if there is > 1 set-cookie header, we have to fix it to be an array of values
	if (headers.has("set-cookie")) {
		const cookieHeaders = headers.getSetCookie();
		if (cookieHeaders.length > 1) {
			// the Headers.entries() API already normalized all header names to lowercase so we can safely index this as 'set-cookie'
			nodeHeaders["set-cookie"] = cookieHeaders;
		}
	}
	return nodeHeaders;
};