handleDocumentRequest hook inside entry.server

[parisholley]

From what I understand, the loadContext functionality seems to be too far up in the stack (server adapter layer) vs being server agnostic. I should be able to expose a buildLoadContext() function inside entry.server.tsx, so that I can effectively bootstrap request resources.

remix/packages/remix-server-runtime/server.ts

Lines 296 to 306 in 1c03a56

	let routeLoaderResults = await Promise.allSettled(
	matchesToLoad.map((match) =>
	match.route.module.loader
	? callRouteLoader({
	loadContext,
	match,
	request,
	})
	: Promise.resolve(undefined)
	)
	);

As you can see in that line in the runtime, we execute all of the loaders in parallel, however there is no way to initiate an asynchronous "pre loader" logic, which would allow us to build data/context and pass it to every loader before they begin.

Use Cases:

• Leveraging a DataLoader to reduce I/O when fetching the same data across loaders
• Leveraging an ORM with a Unit-of-Work pattern (same as above, re-using instances in memory)
• Sharing a request-level object that is often a clone/fork of some instance-wide singleton

The handleRequest method could handle any type of "post loader" logic (eg: rollback/commit transactions), or the alternative to this idea is a truer middleware pattern.

I initially attempted to piggyback off the request object in the loader function, however it is cloned every time so you cannot share anything between them. While there are other potential "global" node.js approaches (async hooks, domains) they are either experimental/deprecated or have performance trade offs.

[parisholley]

alternatively, perhaps loadContext should always return an object (atm is undefined if you never set it on the adapter), and let the loaders potentially mutate it (allowing you to lazy instantiate shared resources)