astro/dist/core/app/entrypoints/virtual/dev.js

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

import fetchable, { isDefaultFetchHandler } from "virtual:astro:fetchable";
import { manifest } from "virtual:astro:manifest";
import { clearActions } from "../../../../actions/load.js";
import { createNonRunnableEnvironment } from "../../../environment/dev-nonrunnable.js";
import { setEnvironment } from "../../../environment/index.js";
import { createConsoleLogger } from "../../../logger/impls/console.js";
import { getLogger, setLogger } from "../../../logger/manifest-logger.js";
import { clearMiddleware } from "../../../middleware/load.js";
import { getRouteCache } from "../../../render/route-cache.js";
import { updateRouteTable } from "../../../routing/route-table.js";
import { DevFacadeApp } from "../../dev-facade.js";
// Prevents duplicate listener registration when `createApp` is called
// repeatedly on the same module instance. When the manifest module is
// invalidated, this whole entrypoint module re-evaluates and re-registers
// against the new manifest object (all per-manifest WeakMap state starts
// fresh).
let hmrWired = false;
export const createApp = ({ streaming } = {}) => {
	// Composition order: logger → environment → facade ctor
	// (which warms the route table) → fetch handler → HMR wiring.
	setLogger(manifest, createConsoleLogger({ level: manifest.logLevel }));
	setEnvironment(manifest, createNonRunnableEnvironment());
	const app = new DevFacadeApp(manifest, streaming);
	// Keep the facade's own DefaultFetchHandler when the virtual module is the
	// built-in fallback: `instanceof` can't recognize the fallback in dev, where
	// its class identity is unstable. https://github.com/withastro/astro/issues/17927
	if (!isDefaultFetchHandler) {
		app.setFetchHandler(fetchable);
	}
	// The HMR listeners target the MANIFEST via the functional core: one
	// atomic route-table replacement is visible to every consumer — matcher,
	// custom-404 fallback, rewrites, error-page lookups, and the
	// `manifestData` accessors — at once.
	if (import.meta.hot && !hmrWired) {
		hmrWired = true;
		import.meta.hot.on("astro:routes-updated", async () => {
			try {
				// Re-import the routes module to get fresh routes
				const { routes: newRoutes } = await import("virtual:astro:routes");
				updateRouteTable(manifest, newRoutes.map((route) => route.routeData));
			} catch (e) {
				// Log error but don't crash - route updates are non-critical
				getLogger(manifest).error("router", `Failed to update routes via HMR:\n ${e}`);
			}
		});
		// Listen for content collection changes via HMR.
		// Clear the route cache so getStaticPaths() is re-evaluated with fresh data.
		import.meta.hot.on("astro:content-changed", () => {
			getRouteCache(manifest).clearAll();
		});
		// Listen for middleware file changes via HMR.
		// Clear the cached middleware so it is re-resolved on the next request.
		import.meta.hot.on("astro:middleware-updated", () => {
			clearMiddleware(manifest);
		});
		// Listen for action file changes via HMR.
		// Clear the cached actions so they are re-resolved on the next request.
		import.meta.hot.on("astro:actions-updated", () => {
			clearActions(manifest);
		});
	}
	return app;
};