Preserve Cloudflare miniflare instance across dev server config restarts

.changeset/fix-cloudflare-miniflare-restart.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes `Expected 'miniflare' to be defined` errors and 404 responses in dev mode when using the Cloudflare adapter and the config file changes. Instead of creating a brand new Vite server on config changes, Astro now performs a Vite in-place restart, allowing the Cloudflare adapter to reuse its existing miniflare instance across restarts.

packages/astro/src/core/dev/restart.ts

@@ -4,35 +4,21 @@ import * as vite from 'vite';
 import { globalContentLayer } from '../../content/instance.js';
 import { attachContentServerListeners } from '../../content/server-listeners.js';
 import { eventCliSession, telemetry } from '../../events/index.js';
+import { runHookConfigDone, runHookConfigSetup } from '../../integrations/hooks.js';
 import { SETTINGS_FILE } from '../../preferences/constants.js';
+import { getPrerenderDefault } from '../../prerender/utils.js';
 import type { AstroSettings } from '../../types/astro.js';
 import type { AstroInlineConfig } from '../../types/public/config.js';
 import { createSettings, resolveConfig } from '../config/index.js';
-import { createNodeLogger } from '../logger/node.js';
+import { createVite } from '../create-vite.js';
 import { collectErrorMetadata } from '../errors/dev/utils.js';
 import { isAstroConfigZodError } from '../errors/errors.js';
 import { createSafeError } from '../errors/index.js';
+import { createNodeLogger } from '../logger/node.js';
 import { formatErrorMessage, warnIfCspWithShiki } from '../messages/runtime.js';
+import { createRoutesList } from '../routing/create-manifest.js';
 import type { Container } from './container.js';
-import { createContainer, startContainer } from './container.js';
-
-async function createRestartedContainer(
-	container: Container,
-	settings: AstroSettings,
-): Promise<Container> {
-	const { logger, fs, inlineConfig } = container;
-	const newContainer = await createContainer({
-		isRestart: true,
-		logger: logger,
-		settings,
-		inlineConfig,
-		fs,
-	});
-
-	await startContainer(newContainer);
-
-	return newContainer;
-}
+import { createContainer } from './container.js';
 
 const configRE = /.*astro.config.(?:mjs|mts|cjs|cts|js|ts)$/;
 
@@ -45,25 +31,20 @@ function shouldRestartContainer(
 	let shouldRestart = false;
 	const normalizedChangedFile = vite.normalizePath(changedFile);
 
-	// If the config file changed, reload the config and restart the server.
 	if (inlineConfig.configFile) {
 		shouldRestart = vite.normalizePath(inlineConfig.configFile) === normalizedChangedFile;
-	}
-	// Otherwise, watch for any astro.config.* file changes in project root
-	else {
+	} else {
 		shouldRestart = configRE.test(normalizedChangedFile);
 		const settingsPath = vite.normalizePath(
 			fileURLToPath(new URL(SETTINGS_FILE, settings.dotAstroDir)),
 		);
 		if (settingsPath.endsWith(normalizedChangedFile)) {
 			shouldRestart = settings.preferences.ignoreNextPreferenceReload ? false : true;
-
 			settings.preferences.ignoreNextPreferenceReload = false;
 		}
 	}
 
 	if (!shouldRestart && settings.watchFiles.length > 0) {
-		// If the config file didn't change, check if any of the watched files changed.
 		shouldRestart = settings.watchFiles.some(
 			(path) => vite.normalizePath(path) === vite.normalizePath(changedFile),
 		);
@@ -72,46 +53,79 @@ function shouldRestartContainer(
 	return shouldRestart;
 }
 
-async function restartContainer(container: Container): Promise<Container | Error> {
-	const { logger, close, settings: existingSettings } = container;
+/**
+ * Restart the dev server in-place by reusing the existing Vite server instance.
+ *
+ * Instead of tearing down and recreating the entire container (which creates a
+ * brand new Vite server), this function re-reads the Astro config, builds a new
+ * Vite inline config with updated plugins, patches it onto the existing server,
+ * then calls Vite's own native restart. Vite's restart does an in-place mutation
+ * of the server object, keeping the same HTTP server / TCP socket alive and
+ * passing `previousEnvironments` to plugins — allowing adapters like
+ * `@cloudflare/vite-plugin` to reuse their miniflare instance rather than
+ * disposing and recreating it.
+ */
+async function restartContainerInPlace(container: Container): Promise<AstroSettings | Error> {
+	const { logger, settings: existingSettings, inlineConfig, fs } = container;
 	container.restartInFlight = true;
 
 	try {
-		const { astroConfig } = await resolveConfig(container.inlineConfig, 'dev', container.fs);
-		if (astroConfig.security.csp) {
-			logger.warn(
-				'config',
-				"Astro's Content Security Policy (CSP) does not work in development mode. To verify your CSP implementation, build the project and run the preview server.",
-			);
-		}
+		const { astroConfig } = await resolveConfig(inlineConfig, 'dev', fs);
 		warnIfCspWithShiki(astroConfig, logger);
-		const settings = await createSettings(
+		let settings = await createSettings(
 			astroConfig,
-			container.inlineConfig.logLevel,
+			inlineConfig.logLevel,
 			fileURLToPath(existingSettings.config.root),
 		);
-		await close();
-		return await createRestartedContainer(container, settings);
+
+		settings = await runHookConfigSetup({ settings, command: 'dev', logger, isRestart: true });
+		if (!settings.adapter?.adapterFeatures?.buildOutput) {
+			settings.buildOutput = getPrerenderDefault(settings.config) ? 'static' : 'server';
+		}
+		await runHookConfigDone({ settings, logger, command: 'dev' });
+
+		const mode = inlineConfig?.mode ?? 'development';
+		const {
+			server: { host, headers, allowedHosts },
+		} = settings.config;
+		const rendererClientEntries = settings.renderers
+			.map((r) => r.clientEntrypoint)
+			.filter(Boolean) as string[];
+		const routesList = await createRoutesList({ settings, fsMod: fs }, logger, { dev: true });
+		const address = container.viteServer.httpServer?.address();
+		const port = address !== null && typeof address === 'object' ? address.port : undefined;
+		const newViteConfig = await createVite(
+			{
+				server: { host, headers, allowedHosts, port },
+				optimizeDeps: { include: rendererClientEntries },
+			},
+			{ settings, logger, mode, command: 'dev', fs, sync: false, routesList },
+		);
+
+		// Resolve the new inline config into a full ResolvedConfig and assign it
+		// onto the existing server so Vite's restartServer() uses the new plugins.
+		container.viteServer.config = await vite.resolveConfig(newViteConfig, 'serve');
+
+		await container.viteServer.restart();
+
+		container.settings = settings;
+		return settings;
 	} catch (_err) {
 		const error = createSafeError(_err);
-		// Print all error messages except ZodErrors from AstroConfig as the pre-logged error is sufficient
 		if (!isAstroConfigZodError(_err)) {
 			logger.error(
 				'config',
 				formatErrorMessage(collectErrorMetadata(error), logger.level() === 'debug') + '\n',
 			);
 		}
-		// Inform connected clients of the config error
-		container.viteServer.environments.client.hot.send({
+		container.viteServer.environments?.client?.hot?.send({
 			type: 'error',
-			err: {
-				message: error.message,
-				stack: error.stack || '',
-			},
+			err: { message: error.message, stack: error.stack || '' },
 		});
-		container.restartInFlight = false;
 		logger.error(null, 'Continuing with previous valid configuration\n');
 		return error;
+	} finally {
+		container.restartInFlight = false;
 	}
 }
 
@@ -132,12 +146,6 @@ export async function createContainerWithAutomaticRestart({
 }: CreateContainerWithAutomaticRestart): Promise<Restart> {
 	const logger = createNodeLogger(inlineConfig ?? {});
 	const { userConfig, astroConfig } = await resolveConfig(inlineConfig ?? {}, 'dev', fs);
-	if (astroConfig.security.csp) {
-		logger.warn(
-			'config',
-			"Astro's Content Security Policy (CSP) does not work in development mode. To verify your CSP implementation, build the project and run the preview server.",
-		);
-	}
 	warnIfCspWithShiki(astroConfig, logger);
 	telemetry.record(eventCliSession('dev', userConfig));
 
@@ -163,7 +171,6 @@ export async function createContainerWithAutomaticRestart({
 		container: initialContainer,
 		bindCLIShortcuts() {
 			const customShortcuts: Array<vite.CLIShortcut> = [
-				// Disable default Vite shortcuts that don't work well with Astro
 				{ key: 'r', description: '' },
 				{ key: 'u', description: '' },
 				{ key: 'c', description: '' },
@@ -185,54 +192,42 @@ export async function createContainerWithAutomaticRestart({
 		},
 	};
 
-	async function handleServerRestart(logMsg = '', server?: vite.ViteDevServer) {
-		logger.info(null, (logMsg + ' Restarting...').trim());
-		const container = restart.container;
-		const result = await restartContainer(container);
-		if (result instanceof Error) {
-			// Failed to restart, use existing container
-			resolveRestart(result);
-		} else {
-			// Restart success. Add new watches because this is a new container with a new Vite server
-			restart.container = result;
-			setupContainer();
-			await attachContentServerListeners(restart.container);
-
-			if (server) {
-				// Vite expects the resolved URLs to be available
-				server.resolvedUrls = result.viteServer.resolvedUrls;
-			}
-
-			resolveRestart(null);
-		}
-		restartComplete = new Promise<Error | null>((resolve) => {
-			resolveRestart = resolve;
-		});
-	}
-
 	function handleChangeRestart(logMsg: string) {
 		return async function (changedFile: string) {
 			if (shouldRestartContainer(restart.container, changedFile)) {
-				handleServerRestart(logMsg);
+				logger.info(null, (logMsg + ' Restarting...').trim());
+				const result = await restartContainerInPlace(restart.container);
+				if (result instanceof Error) {
+					resolveRestart(result);
+				} else {
+					setupContainer();
+					await attachContentServerListeners(restart.container);
+					resolveRestart(null);
+				}
+				restartComplete = new Promise<Error | null>((resolve) => {
+					resolveRestart = resolve;
+				});
 			}
 		};
 	}
 
-	// Set up watchers, vite restart API, and shortcuts
+	let changeHandler: (file: string) => void;
+	let unlinkHandler: (file: string) => void;
+	let addHandler: (file: string) => void;
+
 	function setupContainer() {
 		const watcher = restart.container.viteServer.watcher;
-		watcher.on('change', handleChangeRestart('Configuration file updated.'));
-		watcher.on('unlink', handleChangeRestart('Configuration file removed.'));
-		watcher.on('add', handleChangeRestart('Configuration file added.'));
-
-		// Restart the Astro dev server instead of Vite's when the API is called by plugins.
-		// Ignore the `forceOptimize` parameter for now.
-		restart.container.viteServer.restart = async () => {
-			if (!restart.container.restartInFlight) {
-				await handleServerRestart('', restart.container.viteServer);
-			}
-		};
+		if (changeHandler) watcher.off('change', changeHandler);
+		if (unlinkHandler) watcher.off('unlink', unlinkHandler);
+		if (addHandler) watcher.off('add', addHandler);
+		changeHandler = handleChangeRestart('Configuration file updated.');
+		unlinkHandler = handleChangeRestart('Configuration file removed.');
+		addHandler = handleChangeRestart('Configuration file added.');
+		watcher.on('change', changeHandler);
+		watcher.on('unlink', unlinkHandler);
+		watcher.on('add', addHandler);
 	}
+
 	setupContainer();
 	return restart;
 }

packages/astro/test/units/dev/restart.test.js

@@ -172,9 +172,10 @@ describe('dev container restarts', { timeout: 20000 }, () => {
 		assert.equal(isStarted(restart.container), true);
 
 		try {
-			let restartComplete = restart.restarted();
+			// viteServer.restart() is now handled natively by Vite — just verify
+			// it completes without error and the server is still running.
 			await restart.container.viteServer.restart();
-			await restartComplete;
+			assert.equal(isStarted(restart.container), true);
 		} finally {
 			await restart.container.close();
 		}
@@ -203,4 +204,68 @@ describe('dev container restarts', { timeout: 20000 }, () => {
 			await restart.container.close();
 		}
 	});
+
+	it('Reuses the same viteServer instance on config file change', async () => {
+		cleanupFile('astro.config.mjs');
+		fs.writeFileSync(path.join(fixtureDir, 'astro.config.mjs'), '');
+
+		const restart = await createContainerWithAutomaticRestart({
+			inlineConfig: { ...defaultInlineConfig, root: fixtureDir },
+		});
+		await startContainer(restart.container);
+
+		const originalViteServer = restart.container.viteServer;
+
+		try {
+			let restartComplete = restart.restarted();
+			fs.writeFileSync(path.join(fixtureDir, 'astro.config.mjs'), '');
+			restart.container.viteServer.watcher.emit(
+				'change',
+				path.join(fixtureDir, 'astro.config.mjs').replace(/\\/g, '/'),
+			);
+			await restartComplete;
+
+			// The viteServer object should be the same instance — in-place restart
+			assert.equal(restart.container.viteServer, originalViteServer);
+		} finally {
+			await restart.container.close();
+			cleanupFile('astro.config.mjs');
+		}
+	});
+
+	it('Does not accumulate watcher listeners on repeated restarts', async () => {
+		cleanupFile('astro.config.mjs');
+		fs.writeFileSync(path.join(fixtureDir, 'astro.config.mjs'), '');
+
+		const restart = await createContainerWithAutomaticRestart({
+			inlineConfig: { ...defaultInlineConfig, root: fixtureDir },
+		});
+		await startContainer(restart.container);
+
+		const watcher = restart.container.viteServer.watcher;
+
+		try {
+			// Do a first restart to establish the post-restart listener count
+			let restartComplete = restart.restarted();
+			fs.writeFileSync(path.join(fixtureDir, 'astro.config.mjs'), '// restart 0');
+			watcher.emit('change', path.join(fixtureDir, 'astro.config.mjs').replace(/\\/g, '/'));
+			await restartComplete;
+
+			const listenerCountAfterFirst = watcher.listenerCount('change');
+
+			// Do two more restarts and verify the count stays stable
+			for (let i = 1; i < 3; i++) {
+				restartComplete = restart.restarted();
+				fs.writeFileSync(path.join(fixtureDir, 'astro.config.mjs'), `// restart ${i}`);
+				watcher.emit('change', path.join(fixtureDir, 'astro.config.mjs').replace(/\\/g, '/'));
+				await restartComplete;
+			}
+
+			// Listener count should be stable — old listeners removed before new ones added
+			assert.equal(watcher.listenerCount('change'), listenerCountAfterFirst);
+		} finally {
+			await restart.container.close();
+			cleanupFile('astro.config.mjs');
+		}
+	});
 });