fix: default values in object destructuring

.changeset/clean-planets-rush.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: handle default values in object destructuring within "each" blocks when using characters like "}" and "]"

documentation/docs/98-reference/.generated/compile-errors.md

@@ -988,6 +988,12 @@ Unexpected end of input
 '%word%' is a reserved word in JavaScript and cannot be used here
 ```
 
+### unterminated_string_constant
+
+```
+Unterminated string constant
+```
+
 ### void_element_invalid_content
 
 ```

packages/svelte/messages/compile-errors/template.md

@@ -410,6 +410,10 @@ See https://html.spec.whatwg.org/multipage/custom-elements.html#valid-custom-ele
 
 > '%word%' is a reserved word in JavaScript and cannot be used here
 
+## unterminated_string_constant
+
+> Unterminated string constant
+
 ## void_element_invalid_content
 
 > Void elements cannot have children or closing tags

packages/svelte/src/compiler/errors.js

@@ -1537,6 +1537,15 @@ export function unexpected_reserved_word(node, word) {
 	e(node, "unexpected_reserved_word", `'${word}' is a reserved word in JavaScript and cannot be used here`);
 }
 
+/**
+ * Unterminated string constant
+ * @param {null | number | NodeLike} node
+ * @returns {never}
+ */
+export function unterminated_string_constant(node) {
+	e(node, "unterminated_string_constant", "Unterminated string constant");
+}
+
 /**
  * Void elements cannot have children or closing tags
  * @param {null | number | NodeLike} node

packages/svelte/src/compiler/phases/1-parse/read/context.js

@@ -14,6 +14,8 @@ import { parse_expression_at } from '../acorn.js';
 import { regex_not_newline_characters } from '../../patterns.js';
 import * as e from '../../../errors.js';
 import { locator } from '../../../state.js';
+import read_expression from './expression.js';
+import { is_back_quote, is_quote } from '../utils/quote.js';
 
 /**
  * @param {Parser} parser
@@ -41,33 +43,11 @@ export default function read_pattern(parser) {
 		};
 	}
 
-	if (!is_bracket_open(code)) {
-		e.expected_pattern(i);
-	}
-
-	const bracket_stack = [code];
-	i += code <= 0xffff ? 1 : 2;
-
-	while (i < parser.template.length) {
-		const code = full_char_code_at(parser.template, i);
-		if (is_bracket_open(code)) {
-			bracket_stack.push(code);
-		} else if (is_bracket_close(code)) {
-			const popped = /** @type {number} */ (bracket_stack.pop());
-			if (!is_bracket_pair(popped, code)) {
-				e.expected_token(i, String.fromCharCode(/** @type {number} */ (get_bracket_close(popped))));
-			}
-			if (bracket_stack.length === 0) {
-				i += code <= 0xffff ? 1 : 2;
-				break;
-			}
-		}
-		i += code <= 0xffff ? 1 : 2;
-	}
-
+	i = read_expression_length(parser, start);
 	parser.index = i;
 
 	const pattern_string = parser.template.slice(start, i);
+
 	try {
 		// the length of the `space_with_newline` has to be start - 1
 		// because we added a `(` in front of the pattern_string,
@@ -97,6 +77,95 @@ export default function read_pattern(parser) {
 	}
 }
 
+/**
+ * @param {Parser} parser
+ * @param {number} start
+ */
+function read_expression_length(parser, start) {
+	let i = start;
+	const code = full_char_code_at(parser.template, i);
+
+	if (!is_bracket_open(code)) {
+		e.expected_pattern(i);
+	}
+
+	const bracket_stack = [code];
+	i += code <= 0xffff ? 1 : 2;
+
+	while (i < parser.template.length) {
+		let code = full_char_code_at(parser.template, i);
+		if (is_quote(code)) {
+			i = read_string_length(parser, i, code);
+		} else {
+			if (is_bracket_open(code)) {
+				bracket_stack.push(code);
+			} else if (is_bracket_close(code)) {
+				const popped = /** @type {number} */ (bracket_stack.pop());
+				if (!is_bracket_pair(popped, code)) {
+					e.expected_token(
+						i,
+						String.fromCharCode(/** @type {number} */ (get_bracket_close(popped)))
+					);
+				}
+				if (bracket_stack.length === 0) {
+					i += code <= 0xffff ? 1 : 2;
+					break;
+				}
+			}
+			i += code <= 0xffff ? 1 : 2;
+		}
+	}
+
+	return i;
+}
+
+/**
+ * @param {Parser} parser
+ * @param {number} start
+ * @param {number} quote
+ */
+function read_string_length(parser, start, quote) {
+	let i = start;
+	i += quote <= 0xffff ? 1 : 2;
+
+	const BACKSLASH = '\\'.charCodeAt(0);
+	const DOLAR = '$'.charCodeAt(0);
+	const LEFT_BRACKET = '{'.charCodeAt(0);
+
+	let is_escaped = false;
+	while (i < parser.template.length) {
+		const code = full_char_code_at(parser.template, i);
+		if (!is_escaped && code === quote) {
+			break;
+		}
+
+		if (!is_escaped && code === BACKSLASH) {
+			is_escaped = true;
+		} else if (is_escaped) {
+			is_escaped = false;
+		}
+
+		if (
+			i < parser.template.length - 1 &&
+			is_back_quote(quote) &&
+			code === DOLAR &&
+			full_char_code_at(parser.template, i + 1) === LEFT_BRACKET
+		) {
+			i++;
+			i = read_expression_length(parser, i);
+		} else {
+			i += code <= 0xffff ? 1 : 2;
+		}
+	}
+
+	const code = full_char_code_at(parser.template, i);
+	if (code !== quote) {
+		e.unterminated_string_constant(start);
+	}
+
+	return i + (code <= 0xffff ? 1 : 2);
+}
+
 /**
  * @param {Parser} parser
  * @returns {any}

packages/svelte/src/compiler/phases/1-parse/utils/quote.js

@@ -0,0 +1,13 @@
+const SINGLE_QUOTE = "'".charCodeAt(0);
+const DOUBLE_QUOTE = '"'.charCodeAt(0);
+const BACK_QUOTE = '`'.charCodeAt(0);
+
+/** @param {number} code */
+export function is_quote(code) {
+	return code === SINGLE_QUOTE || code === DOUBLE_QUOTE || code === BACK_QUOTE;
+}
+
+/** @param {number} code */
+export function is_back_quote(code) {
+	return code === BACK_QUOTE;
+}

packages/svelte/tests/parser-modern/samples/each-block-object-pattern-special-characters/input.svelte

@@ -0,0 +1,9 @@
+{#each x as { y = 'z' }}{/each}
+
+{#each x as { y = '{' }}{/each}
+
+{#each x as { y = ']' }}{/each}
+
+{#each x as { y = `${`"`}` }}{/each}
+
+{#each x as { y = `${`John`}` }}{/each}