chore: use codePointAt instead of implementing it ourselves (#14923)

 seems to be some sort of codePointAt polyfill from ancient times before that was available on String.prototype

Author: Rich-Harris

packages/svelte/src/compiler/phases/1-parse/index.js

@@ -3,7 +3,6 @@
 import { isIdentifierStart, isIdentifierChar } from 'acorn';
 import fragment from './state/fragment.js';
 import { regex_whitespace } from '../patterns.js';
-import full_char_code_at from './utils/full_char_code_at.js';
 import * as e from '../../errors.js';
 import { create_fragment } from './utils/create.js';
 import read_options from './read/options.js';
@@ -230,13 +229,13 @@ export class Parser {
 
 		let i = this.index;
 
-		const code = full_char_code_at(this.template, i);
+		const code = /** @type {number} */ (this.template.codePointAt(i));
 		if (!isIdentifierStart(code, true)) return null;
 
 		i += code <= 0xffff ? 1 : 2;
 
 		while (i < this.template.length) {
-			const code = full_char_code_at(this.template, i);
+			const code = /** @type {number} */ (this.template.codePointAt(i));
 
 			if (!isIdentifierChar(code, true)) break;
 			i += code <= 0xffff ? 1 : 2;

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

@@ -1,15 +1,7 @@
 /** @import { Location } from 'locate-character' */
 /** @import { Pattern } from 'estree' */
 /** @import { Parser } from '../index.js' */
-// @ts-expect-error acorn type definitions are borked in the release we use
-import { isIdentifierStart } from 'acorn';
-import full_char_code_at from '../utils/full_char_code_at.js';
-import {
-	is_bracket_open,
-	is_bracket_close,
-	is_bracket_pair,
-	get_bracket_close
-} from '../utils/bracket.js';
+import { is_bracket_open, is_bracket_close, get_bracket_close } from '../utils/bracket.js';
 import { parse_expression_at } from '../acorn.js';
 import { regex_not_newline_characters } from '../../patterns.js';
 import * as e from '../../../errors.js';
@@ -23,9 +15,9 @@ export default function read_pattern(parser) {
 	const start = parser.index;
 	let i = parser.index;
 
-	const code = full_char_code_at(parser.template, i);
-	if (isIdentifierStart(code, true)) {
-		const name = /** @type {string} */ (parser.read_identifier());
+	const name = parser.read_identifier();
+
+	if (name !== null) {
 		const annotation = read_type_annotation(parser);
 
 		return {
@@ -41,28 +33,32 @@ export default function read_pattern(parser) {
 		};
 	}
 
-	if (!is_bracket_open(code)) {
+	if (!is_bracket_open(parser.template[i])) {
 		e.expected_pattern(i);
 	}
 
-	const bracket_stack = [code];
-	i += code <= 0xffff ? 1 : 2;
+	/** @type {string[]} */
+	const bracket_stack = [];
 
 	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))));
+		const char = parser.template[i];
+
+		if (is_bracket_open(char)) {
+			bracket_stack.push(char);
+		} else if (is_bracket_close(char)) {
+			const popped = /** @type {string} */ (bracket_stack.pop());
+			const expected = /** @type {string} */ (get_bracket_close(popped));
+
+			if (char !== expected) {
+				e.expected_token(i, expected);
 			}
+
 			if (bracket_stack.length === 0) {
-				i += code <= 0xffff ? 1 : 2;
+				i += 1;
 				break;
 			}
 		}
-		i += code <= 0xffff ? 1 : 2;
+		i += 1;
 	}
 
 	parser.index = i;

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

@@ -1,41 +1,30 @@
-import full_char_code_at from './full_char_code_at.js';
+const SQUARE_BRACKET_OPEN = '[';
+const SQUARE_BRACKET_CLOSE = ']';
+const CURLY_BRACKET_OPEN = '{';
+const CURLY_BRACKET_CLOSE = '}';
+const PARENTHESES_OPEN = '(';
+const PARENTHESES_CLOSE = ')';
 
-const SQUARE_BRACKET_OPEN = '['.charCodeAt(0);
-const SQUARE_BRACKET_CLOSE = ']'.charCodeAt(0);
-const CURLY_BRACKET_OPEN = '{'.charCodeAt(0);
-const CURLY_BRACKET_CLOSE = '}'.charCodeAt(0);
-const PARENTHESES_OPEN = '('.charCodeAt(0);
-const PARENTHESES_CLOSE = ')'.charCodeAt(0);
-
-/** @param {number} code */
-export function is_bracket_open(code) {
-	return code === SQUARE_BRACKET_OPEN || code === CURLY_BRACKET_OPEN;
+/** @param {string} char */
+export function is_bracket_open(char) {
+	return char === SQUARE_BRACKET_OPEN || char === CURLY_BRACKET_OPEN;
 }
 
-/** @param {number} code */
-export function is_bracket_close(code) {
-	return code === SQUARE_BRACKET_CLOSE || code === CURLY_BRACKET_CLOSE;
+/** @param {string} char */
+export function is_bracket_close(char) {
+	return char === SQUARE_BRACKET_CLOSE || char === CURLY_BRACKET_CLOSE;
 }
 
-/**
- * @param {number} open
- * @param {number} close
- */
-export function is_bracket_pair(open, close) {
-	return (
-		(open === SQUARE_BRACKET_OPEN && close === SQUARE_BRACKET_CLOSE) ||
-		(open === CURLY_BRACKET_OPEN && close === CURLY_BRACKET_CLOSE)
-	);
-}
-
-/** @param {number} open */
+/** @param {string} open */
 export function get_bracket_close(open) {
 	if (open === SQUARE_BRACKET_OPEN) {
 		return SQUARE_BRACKET_CLOSE;
 	}
+
 	if (open === CURLY_BRACKET_OPEN) {
 		return CURLY_BRACKET_CLOSE;
 	}
+
 	if (open === PARENTHESES_OPEN) {
 		return PARENTHESES_CLOSE;
 	}
@@ -132,8 +121,7 @@ function count_leading_backslashes(string, search_start_index) {
  * @returns {number | undefined} The index of the closing bracket, or undefined if not found.
  */
 export function find_matching_bracket(template, index, open) {
-	const open_code = full_char_code_at(open, 0);
-	const close_code = get_bracket_close(open_code);
+	const close = get_bracket_close(open);
 	let brackets = 1;
 	let i = index;
 	while (brackets > 0 && i < template.length) {
@@ -159,10 +147,10 @@ export function find_matching_bracket(template, index, open) {
 				continue;
 			}
 			default: {
-				const code = full_char_code_at(template, i);
-				if (code === open_code) {
+				const char = template[i];
+				if (char === open) {
 					brackets++;
-				} else if (code === close_code) {
+				} else if (char === close) {
 					brackets--;
 				}
 				if (brackets === 0) {