fix: parse regexp without parens

.changeset/six-ears-fly.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: parse regexp without parens

packages/svelte/src/compiler/parse/state/mustache.js

@@ -40,7 +40,7 @@ export default function mustache(parser) {
 	parser.index += 1;
 	parser.allow_whitespace();
 	// {/if}, {/each}, {/await} or {/key}
-	if (parser.eat('/')) {
+	if (parser.match('/')) {
 		let block = parser.current();
 		let expected;
 		if (closing_tag_omitted(block.name)) {
@@ -68,8 +68,19 @@ export default function mustache(parser) {
 		} else if (block.type === 'KeyBlock') {
 			expected = 'key';
 		} else {
-			parser.error(parser_errors.unexpected_block_close);
+			let possible_regex = read_expression(parser);
+			parser.allow_whitespace();
+			parser.eat('}', true);
+			parser.current().children.push({
+				start,
+				end: parser.index,
+				type: 'MustacheTag',
+				expression: possible_regex
+			});
+			return;
 		}
+		parser.index += 1;
+
 		parser.eat(expected, true);
 		parser.allow_whitespace();
 		parser.eat('}', true);

packages/svelte/test/parser/parser.test.js

@@ -1,7 +1,8 @@
 import * as fs from 'node:fs';
 import { assert, describe, it } from 'vitest';
 import * as svelte from 'svelte/compiler';
-import { try_load_json } from '../helpers.js';
+import { try_load_json, try_read_file } from '../helpers.js';
+import { walk } from 'estree-walker';
 
 describe('parse', () => {
 	fs.readdirSync(`${__dirname}/samples`).forEach((dir) => {
@@ -26,8 +27,23 @@ describe('parse', () => {
 				.trimEnd()
 				.replace(/\r/g, '');
 
-			const expectedOutput = try_load_json(`${__dirname}/samples/${dir}/output.json`);
-			const expectedError = try_load_json(`${__dirname}/samples/${dir}/error.json`);
+			const output_file = try_read_file(`${__dirname}/samples/${dir}/output.json`);
+
+			// Regexp literals are serialized as empty objects, so we need to convert the values back to RegExp
+			// to make the deepEqual comparison work.
+			let expectedOutput = output_file
+				? JSON.parse(output_file, (key, value) => {
+						if (
+							typeof value === 'object' &&
+							value !== null &&
+							value.type === 'Literal' &&
+							value.regex
+						) {
+							value.value = new RegExp(value.regex.pattern, value.regex.flags);
+						}
+						return value;
+				  })
+				: null;
 
 			try {
 				const { ast } = svelte.compile(
@@ -48,6 +64,8 @@ describe('parse', () => {
 				assert.deepEqual(ast.module, expectedOutput.module);
 			} catch (err) {
 				if (err.name !== 'ParseError') throw err;
+
+				const expectedError = try_load_json(`${__dirname}/samples/${dir}/error.json`);
 				if (!expectedError) throw err;
 				const { code, message, pos, start } = err;
 

packages/svelte/test/parser/samples/inline-regex/input.svelte

@@ -0,0 +1 @@
+{/abc/.test("abc")}

packages/svelte/test/parser/samples/inline-regex/output.json

@@ -0,0 +1,102 @@
+{
+	"html": {
+		"start": 0,
+		"end": 19,
+		"type": "Fragment",
+		"children": [
+			{
+				"start": 0,
+				"end": 19,
+				"type": "MustacheTag",
+				"expression": {
+					"type": "CallExpression",
+					"start": 1,
+					"end": 18,
+					"loc": {
+						"start": {
+							"line": 1,
+							"column": 1
+						},
+						"end": {
+							"line": 1,
+							"column": 18
+						}
+					},
+					"callee": {
+						"type": "MemberExpression",
+						"start": 1,
+						"end": 11,
+						"loc": {
+							"start": {
+								"line": 1,
+								"column": 1
+							},
+							"end": {
+								"line": 1,
+								"column": 11
+							}
+						},
+						"object": {
+							"type": "Literal",
+							"start": 1,
+							"end": 6,
+							"loc": {
+								"start": {
+									"line": 1,
+									"column": 1
+								},
+								"end": {
+									"line": 1,
+									"column": 6
+								}
+							},
+							"raw": "/abc/",
+							"regex": {
+								"pattern": "abc",
+								"flags": ""
+							}
+						},
+						"property": {
+							"type": "Identifier",
+							"start": 7,
+							"end": 11,
+							"loc": {
+								"start": {
+									"line": 1,
+									"column": 7
+								},
+								"end": {
+									"line": 1,
+									"column": 11
+								}
+							},
+							"name": "test"
+						},
+						"computed": false,
+						"optional": false
+					},
+					"arguments": [
+						{
+							"type": "Literal",
+							"start": 12,
+							"end": 17,
+							"loc": {
+								"start": {
+									"line": 1,
+									"column": 12
+								},
+								"end": {
+									"line": 1,
+									"column": 17
+								}
+							},
+							"value": "abc",
+							"raw": "\"abc\""
+						}
+					],
+					"optional": false
+				}
+			}
+		]
+	}
+}