chore(middleware): lift restriction around serializable data (#7174)

5 files changed, 7 insertions, 113 deletions

diff --git a/.changeset/fuzzy-cycles-trade.md b/.changeset/fuzzy-cycles-trade.md
new file mode 100644
index 000000000..cfea1a58f
--- /dev/null
+++ b/.changeset/fuzzy-cycles-trade.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Remove restriction around serialisable data for `Astro.locals`
diff --git a/packages/astro/src/core/endpoint/index.ts b/packages/astro/src/core/endpoint/index.ts
index 7d298a802..890ed3a73 100644
--- a/packages/astro/src/core/endpoint/index.ts
+++ b/packages/astro/src/core/endpoint/index.ts
@@ -16,8 +16,6 @@ import { AstroCookies, attachToResponse } from '../cookies/index.js';
 import { AstroError, AstroErrorData } from '../errors/index.js';
 import { warn, type LogOptions } from '../logger/core.js';
 import { callMiddleware } from '../middleware/callMiddleware.js';
-import { isValueSerializable } from '../render/core.js';
-
 const clientAddressSymbol = Symbol.for('astro.clientAddress');
 const clientLocalsSymbol = Symbol.for('astro.locals');
 
@@ -117,12 +115,6 @@ export async function callEndpoint<MiddlewareResult = Response | EndpointOutput>
 			onRequest,
 			context,
 			async () => {
-				if (env.mode === 'development' && !isValueSerializable(context.locals)) {
-					throw new AstroError({
-						...AstroErrorData.LocalsNotSerializable,
-						message: AstroErrorData.LocalsNotSerializable.message(ctx.pathname),
-					});
-				}
 				return await renderEndpoint(mod, context, env.ssr);
 			}
 		);
diff --git a/packages/astro/src/core/errors/errors-data.ts b/packages/astro/src/core/errors/errors-data.ts
index 15d0f7056..a97c18d0e 100644
--- a/packages/astro/src/core/errors/errors-data.ts
+++ b/packages/astro/src/core/errors/errors-data.ts
@@ -693,32 +693,6 @@ See https://docs.astro.build/en/guides/server-side-rendering/ for more informati
 			'`locals` can only be assigned to an object. Other values like numbers, strings, etc. are not accepted.',
 		hint: 'If you tried to remove some information from the `locals` object, try to use `delete` or set the property to `undefined`.',
 	},
-
-	/**
-	 * @docs
-	 * @description
-	 * Thrown in development mode when a user attempts to store something that is not serializable in `locals`.
-	 *
-	 * For example:
-	 * ```ts
-	 * import {defineMiddleware} from "astro/middleware";
-	 * export const onRequest = defineMiddleware((context, next) => {
-	 *   context.locals = {
-	 *     foo() {
-	 *       alert("Hello world!")
-	 *     }
-	 *   };
-	 *   return next();
-	 * });
-	 * ```
-	 */
-	LocalsNotSerializable: {
-		title: '`Astro.locals` is not serializable',
-		code: 3034,
-		message: (href: string) => {
-			return `The information stored in \`Astro.locals\` for the path "${href}" is not serializable.\nMake sure you store only serializable data.`;
-		},
-	},
 	// No headings here, that way Vite errors are merged with Astro ones in the docs, which makes more sense to users.
 	// Vite Errors - 4xxx
 	/**
diff --git a/packages/astro/src/core/render/core.ts b/packages/astro/src/core/render/core.ts
index 2d6fb088e..24bec9d30 100644
--- a/packages/astro/src/core/render/core.ts
+++ b/packages/astro/src/core/render/core.ts
@@ -116,16 +116,8 @@ export async function renderPage({ mod, renderContext, env, apiContext }: Render
 	if (!Component)
 		throw new Error(`Expected an exported Astro component but received typeof ${typeof Component}`);
 
-	let locals = {};
-	if (apiContext) {
-		if (env.mode === 'development' && !isValueSerializable(apiContext.locals)) {
-			throw new AstroError({
-				...AstroErrorData.LocalsNotSerializable,
-				message: AstroErrorData.LocalsNotSerializable.message(renderContext.pathname),
-			});
-		}
-		locals = apiContext.locals;
-	}
+	let locals = apiContext?.locals ?? {};
+
 	const result = createResult({
 		adapterName: env.adapterName,
 		links: renderContext.links,
@@ -171,57 +163,3 @@ export async function renderPage({ mod, renderContext, env, apiContext }: Render
 
 	return response;
 }
-
-/**
- * Checks whether any value can is serializable.
- *
- * A serializable value contains plain values. For example, `Proxy`, `Set`, `Map`, functions, etc.
- * are not serializable objects.
- *
- * @param object
- */
-export function isValueSerializable(value: unknown): boolean {
-	let type = typeof value;
-	let plainObject = true;
-	if (type === 'object' && isPlainObject(value)) {
-		for (const [, nestedValue] of Object.entries(value)) {
-			if (!isValueSerializable(nestedValue)) {
-				plainObject = false;
-				break;
-			}
-		}
-	} else {
-		plainObject = false;
-	}
-	let result =
-		value === null ||
-		type === 'string' ||
-		type === 'number' ||
-		type === 'boolean' ||
-		Array.isArray(value) ||
-		plainObject;
-
-	return result;
-}
-
-/**
- *
- * From [redux-toolkit](https://github.com/reduxjs/redux-toolkit/blob/master/packages/toolkit/src/isPlainObject.ts)
- *
- * Returns true if the passed value is "plain" object, i.e. an object whose
- * prototype is the root `Object.prototype`. This includes objects created
- * using object literals, but not for instance for class instances.
- */
-function isPlainObject(value: unknown): value is object {
-	if (typeof value !== 'object' || value === null) return false;
-
-	let proto = Object.getPrototypeOf(value);
-	if (proto === null) return true;
-
-	let baseProto = proto;
-	while (Object.getPrototypeOf(baseProto) !== null) {
-		baseProto = Object.getPrototypeOf(baseProto);
-	}
-
-	return proto === baseProto;
-}
diff --git a/packages/astro/test/middleware.test.js b/packages/astro/test/middleware.test.js
index 8e2e0dd0a..270666678 100644
--- a/packages/astro/test/middleware.test.js
+++ b/packages/astro/test/middleware.test.js
@@ -61,12 +61,6 @@ describe('Middleware in DEV mode', () => {
 		expect($('p').html()).to.equal('Not interested');
 	});
 
-	it('should throw an error when locals are not serializable', async () => {
-		let html = await fixture.fetch('/broken-locals').then((res) => res.text());
-		let $ = cheerio.load(html);
-		expect($('title').html()).to.equal('LocalsNotSerializable');
-	});
-
 	it("should throw an error when the middleware doesn't call next or doesn't return a response", async () => {
 		let html = await fixture.fetch('/does-nothing').then((res) => res.text());
 		let $ = cheerio.load(html);
@@ -180,15 +174,6 @@ describe('Middleware API in PROD mode, SSR', () => {
 		expect($('p').html()).to.equal('Not interested');
 	});
 
-	it('should NOT throw an error when locals are not serializable', async () => {
-		const app = await fixture.loadTestAdapterApp();
-		const request = new Request('http://example.com/broken-locals');
-		const response = await app.render(request);
-		const html = await response.text();
-		const $ = cheerio.load(html);
-		expect($('title').html()).to.not.equal('LocalsNotSerializable');
-	});
-
 	it("should throws an error when the middleware doesn't call next or doesn't return a response", async () => {
 		const app = await fixture.loadTestAdapterApp();
 		const request = new Request('http://example.com/does-nothing');