Handle unhandledrejections in the dev server (#9424)

* Handle unhandledrejections in the dev server

* Adding changeset

* Update .changeset/curvy-lobsters-crash.md

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>

* Use AsyncLocalStorage

* Return errorWithMetadata

* Send the error to the browser

---------

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>

5 files changed, 82 insertions, 26 deletions

diff --git a/.changeset/curvy-lobsters-crash.md b/.changeset/curvy-lobsters-crash.md
new file mode 100644
index 000000000..f3ccdb436
--- /dev/null
+++ b/.changeset/curvy-lobsters-crash.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Prevents dev server from crashing on unhandled rejections, and adds a helpful error message
diff --git a/packages/astro/src/core/errors/errors-data.ts b/packages/astro/src/core/errors/errors-data.ts
index 5c30495d6..8e8fb3911 100644
--- a/packages/astro/src/core/errors/errors-data.ts
+++ b/packages/astro/src/core/errors/errors-data.ts
@@ -1292,3 +1292,12 @@ export const CantRenderPage = {
 
 // Generic catch-all - Only use this in extreme cases, like if there was a cosmic ray bit flip
 export const UnknownError = { name: 'UnknownError', title: 'Unknown Error.' } satisfies ErrorData;
+
+export const UnhandledRejection = {
+	name: 'UnhandledRejection',
+	title: 'Unhandled rejection',
+	message: (stack: string) => {
+		return `Astro detected an unhandled rejection. Here's the stack trace:\n${stack}`;
+	},
+	hint: 'Make sure your promises all have an `await` or a `.catch()` handler.'
+}
diff --git a/packages/astro/src/vite-plugin-astro-server/error.ts b/packages/astro/src/vite-plugin-astro-server/error.ts
new file mode 100644
index 000000000..d29647f98
--- /dev/null
+++ b/packages/astro/src/vite-plugin-astro-server/error.ts
@@ -0,0 +1,33 @@
+import type { ModuleLoader } from '../core/module-loader/index.js'
+import type { AstroConfig } from '../@types/astro.js';
+import type DevPipeline from './devPipeline.js';
+
+import { collectErrorMetadata } from '../core/errors/dev/index.js';
+import { createSafeError } from '../core/errors/index.js';
+import { formatErrorMessage } from '../core/messages.js';
+import { eventError, telemetry } from '../events/index.js';
+
+export function recordServerError(loader: ModuleLoader, config: AstroConfig, pipeline: DevPipeline, _err: unknown) {
+	const err = createSafeError(_err);
+
+	// This could be a runtime error from Vite's SSR module, so try to fix it here
+	try {
+		loader.fixStacktrace(err);
+	} catch {}
+
+	// This is our last line of defense regarding errors where we still might have some information about the request
+	// Our error should already be complete, but let's try to add a bit more through some guesswork
+	const errorWithMetadata = collectErrorMetadata(err, config.root);
+
+	telemetry.record(eventError({ cmd: 'dev', err: errorWithMetadata, isFatal: false }));
+
+	pipeline.logger.error(
+		null,
+		formatErrorMessage(errorWithMetadata, pipeline.logger.level() === 'debug')
+	);
+
+	return {
+		error: err,
+		errorWithMetadata
+	};
+}
diff --git a/packages/astro/src/vite-plugin-astro-server/plugin.ts b/packages/astro/src/vite-plugin-astro-server/plugin.ts
index f0df0e3eb..6969184f2 100644
--- a/packages/astro/src/vite-plugin-astro-server/plugin.ts
+++ b/packages/astro/src/vite-plugin-astro-server/plugin.ts
@@ -10,6 +10,12 @@ import { baseMiddleware } from './base.js';
 import { createController } from './controller.js';
 import DevPipeline from './devPipeline.js';
 import { handleRequest } from './request.js';
+import { AstroError, AstroErrorData } from '../core/errors/index.js';
+import { getViteErrorPayload } from '../core/errors/dev/index.js';
+import { AsyncLocalStorage } from 'node:async_hooks';
+import { IncomingMessage } from 'node:http';
+import { setRouteError } from './server-state.js';
+import { recordServerError } from './error.js';
 
 export interface AstroPluginOptions {
 	settings: AstroSettings;
@@ -30,6 +36,7 @@ export default function createVitePluginAstroServer({
 			const pipeline = new DevPipeline({ logger, manifest, settings, loader });
 			let manifestData: ManifestData = createRouteManifest({ settings, fsMod }, logger);
 			const controller = createController({ loader });
+			const localStorage = new AsyncLocalStorage();
 
 			/** rebuild the route cache + manifest, as needed. */
 			function rebuildManifest(needsManifestRebuild: boolean) {
@@ -43,6 +50,22 @@ export default function createVitePluginAstroServer({
 			viteServer.watcher.on('unlink', rebuildManifest.bind(null, true));
 			viteServer.watcher.on('change', rebuildManifest.bind(null, false));
 
+			function handleUnhandledRejection(rejection: any) {
+				const error = new AstroError({
+					...AstroErrorData.UnhandledRejection,
+					message: AstroErrorData.UnhandledRejection.message(rejection?.stack || rejection)
+				});
+				const store = localStorage.getStore();
+				if(store instanceof IncomingMessage) {
+					const request = store;
+					setRouteError(controller.state, request.url!, error);
+				}
+				const { errorWithMetadata } = recordServerError(loader, settings.config, pipeline, error);
+				setTimeout(async () => loader.webSocketSend(await getViteErrorPayload(errorWithMetadata)), 200)
+			}
+
+			process.on('unhandledRejection', handleUnhandledRejection);
+
 			return () => {
 				// Push this middleware to the front of the stack so that it can intercept responses.
 				// fix(#6067): always inject this to ensure zombie base handling is killed after restarts
@@ -57,13 +80,15 @@ export default function createVitePluginAstroServer({
 						response.end();
 						return;
 					}
-					handleRequest({
-						pipeline,
-						manifestData,
-						controller,
-						incomingRequest: request,
-						incomingResponse: response,
-						manifest,
+					localStorage.run(request, () => {
+						handleRequest({
+							pipeline,
+							manifestData,
+							controller,
+							incomingRequest: request,
+							incomingResponse: response,
+							manifest,
+						});
 					});
 				});
 			};
diff --git a/packages/astro/src/vite-plugin-astro-server/request.ts b/packages/astro/src/vite-plugin-astro-server/request.ts
index aa9124fb4..f0c6b3de0 100644
--- a/packages/astro/src/vite-plugin-astro-server/request.ts
+++ b/packages/astro/src/vite-plugin-astro-server/request.ts
@@ -11,6 +11,7 @@ import { runWithErrorHandling } from './controller.js';
 import type DevPipeline from './devPipeline.js';
 import { handle500Response } from './response.js';
 import { handleRoute, matchRoute } from './route.js';
+import { recordServerError } from './error.js';
 
 type HandleRequest = {
 	pipeline: DevPipeline;
@@ -89,26 +90,9 @@ export async function handleRequest({
 			});
 		},
 		onError(_err) {
-			const err = createSafeError(_err);
-
-			// This could be a runtime error from Vite's SSR module, so try to fix it here
-			try {
-				moduleLoader.fixStacktrace(err);
-			} catch {}
-
-			// This is our last line of defense regarding errors where we still might have some information about the request
-			// Our error should already be complete, but let's try to add a bit more through some guesswork
-			const errorWithMetadata = collectErrorMetadata(err, config.root);
-
-			telemetry.record(eventError({ cmd: 'dev', err: errorWithMetadata, isFatal: false }));
-
-			pipeline.logger.error(
-				null,
-				formatErrorMessage(errorWithMetadata, pipeline.logger.level() === 'debug')
-			);
+			const { error, errorWithMetadata } = recordServerError(moduleLoader, config, pipeline, _err);
 			handle500Response(moduleLoader, incomingResponse, errorWithMetadata);
-
-			return err;
+			return error;
 		},
 	});
 }