Add errors for unknown experimental keys

.changeset/red-eggs-speak.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Throw an error when unknown experimental keys are present

packages/astro/src/core/config/schema.ts

@@ -201,6 +201,17 @@ export const AstroConfigSchema = z.object({
 				.default(ASTRO_CONFIG_DEFAULTS.experimental.inlineStylesheets),
 			middleware: z.oboolean().optional().default(ASTRO_CONFIG_DEFAULTS.experimental.middleware),
 		})
+    .passthrough()
+    .refine(d => {
+      const validKeys = Object.keys(ASTRO_CONFIG_DEFAULTS.experimental)
+      const invalidKeys = Object.keys(d).filter(key => !validKeys.includes(key))
+      if (invalidKeys.length > 0) return false
+      return true
+    }, d => {
+      const validKeys = Object.keys(ASTRO_CONFIG_DEFAULTS.experimental)
+      const invalidKeys = Object.keys(d).filter(key => !validKeys.includes(key))
+      return { message: `Invalid experimental key: \`${invalidKeys.join(', ')}\`. \nMake sure the spelling is correct, and that your Astro version supports this experiment.\nSee https://docs.astro.build/en/reference/configuration-reference/#experimental-flags for more information.` };
+    })
 		.optional()
 		.default({}),
 	legacy: z.object({}).optional().default({}),

packages/astro/test/custom-elements.test.js

@@ -8,9 +8,6 @@ describe('Custom Elements', () => {
 	before(async () => {
 		fixture = await loadFixture({
 			root: './fixtures/custom-elements/',
-			experimental: {
-				integrations: true,
-			},
 		});
 		await fixture.build();
 	});

packages/astro/test/fixtures/custom-elements/astro.config.mjs

@@ -3,7 +3,4 @@ import ceIntegration from '@test/custom-element-renderer';
 
 export default defineConfig({
 	integrations: [ceIntegration()],
-	experimental: {
-		integrations: true
-	}
 })

packages/astro/test/ssr-prerender-404.test.js

@@ -11,9 +11,6 @@ describe('SSR: prerender 404', () => {
 			root: './fixtures/ssr-prerender-404/',
 			output: 'server',
 			adapter: testAdapter(),
-			experimental: {
-				prerender: true,
-			},
 		});
 		await fixture.build();
 	});

packages/astro/test/ssr-prerender.test.js

@@ -12,9 +12,6 @@ describe('SSR: prerender', () => {
 			root: './fixtures/ssr-prerender/',
 			output: 'server',
 			adapter: testAdapter(),
-			experimental: {
-				prerender: true,
-			},
 		});
 		await fixture.build();
 	});