astro/dist/vite-plugin-load-fallback/index.js

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

import nodeFs from "node:fs";
import npath from "node:path";
import { slash } from "../core/path.js";
import { cleanUrl } from "../vite-plugin-utils/index.js";
const FALLBACK_FLAG = "astroFallbackFlag";
export default function loadFallbackPlugin({ fs, root }) {
	// Only add this plugin if a custom fs implementation is provided.
	// Also check for `fs.default` because `import * as fs from 'node:fs'` will
	// export as so, which only it's `.default` would === `nodeFs`.
	// @ts-expect-error check default
	if (!fs || fs === nodeFs || fs.default === nodeFs) {
		return [];
	}
	const tryLoadModule = async (id) => {
		try {
			// await is necessary for the catch
			return await fs.promises.readFile(cleanUrl(id), "utf-8");
		} catch {
			try {
				return await fs.promises.readFile(id, "utf-8");
			} catch {
				try {
					const fullpath = new URL("." + id, root);
					return await fs.promises.readFile(fullpath, "utf-8");
				} catch {}
			}
		}
	};
	return [{
		name: "astro:load-fallback",
		enforce: "post",
		async resolveId(id, parent) {
			// See if this can be loaded from our fs
			if (parent) {
				const candidateId = npath.posix.join(npath.posix.dirname(slash(parent)), id);
				try {
					// Check to see if this file exists and is not a directory.
					const stats = await fs.promises.stat(candidateId);
					if (!stats.isDirectory()) {
						const params = new URLSearchParams(FALLBACK_FLAG);
						return `${candidateId}?${params.toString()}`;
					}
				} catch {}
			}
		},
		load: {
			filter: { id: new RegExp(`(?:\\?|&)${FALLBACK_FLAG}(?:&|=|$)`) },
			async handler(id) {
				const code = await tryLoadModule(id.slice(0, -(1 + FALLBACK_FLAG.length)));
				if (code) {
					return { code };
				}
			}
		}
	}, {
		name: "astro:load-fallback-hmr",
		enforce: "pre",
		handleHotUpdate(context) {
			// Wrap context.read so it checks our filesystem first.
			const read = context.read;
			context.read = async () => {
				const source = await tryLoadModule(context.file);
				if (source) return source;
				return read.call(context);
			};
		}
	}];
}