fix: persist RegExp flags during serialization

.changeset/silly-ants-complain.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Persist RegExp flags during serialization

packages/astro/src/runtime/server/astro-island.ts

@@ -20,7 +20,10 @@ declare const Astro: {
 	const propTypes: PropTypeSelector = {
 		0: (value) => value,
 		1: (value) => JSON.parse(value, reviver),
-		2: (value) => new RegExp(value),
+		2: (value) => {
+			const [source, flags] = JSON.parse(value);
+			return new RegExp(source, flags);
+		},
 		3: (value) => new Date(value),
 		4: (value) => new Map(JSON.parse(value, reviver)),
 		5: (value) => new Set(JSON.parse(value, reviver)),

packages/astro/src/runtime/server/serialize.ts

@@ -62,7 +62,7 @@ function convertToSerializedForm(
 			return [PROP_TYPE.Date, (value as Date).toISOString()];
 		}
 		case '[object RegExp]': {
-			return [PROP_TYPE.RegExp, (value as RegExp).source];
+			return [PROP_TYPE.RegExp, JSON.stringify([(value as RegExp).source, (value as RegExp).flags])];
 		}
 		case '[object Map]': {
 			return [

packages/astro/test/serialize.test.js

@@ -14,7 +14,12 @@ describe('serialize', () => {
 	});
 	it('serializes a regular expression', () => {
 		const input = { a: /b/ };
-		const output = `{"a":[2,"b"]}`;
+		const output = `{"a":[2,"[\\"b\\",\\"\\"]"]}`;
+		expect(serializeProps(input)).to.equal(output);
+	});
+	it('serializes a regular expression with flags', () => {
+		const input = { a: /b/gim };
+		const output = `{"a":[2,"[\\"b\\",\\"gim\\"]"]}`;
 		expect(serializeProps(input)).to.equal(output);
 	});
 	it('serializes a Date', () => {