From a1b857cc5a77af1ffae73355d9c467dce058e427 Mon Sep 17 00:00:00 2001
From: Anthony Fu <anthonyfu117@hotmail.com>
Date: Wed, 3 Apr 2024 23:51:19 +0200
Subject: [PATCH] perf: avoid create uncessary overrides for `replace`

---
 README.md           |  2 +-
 package-lock.json   |  2 +-
 package.json        |  1 +
 src/MagicString.js  | 34 ++++++++++++++++++++++------------
 test/MagicString.js | 19 +++++++++++++++++++
 5 files changed, 44 insertions(+), 14 deletions(-)

diff --git a/README.md b/README.md
index 995565f..6ef18c5 100644
--- a/README.md
+++ b/README.md
@@ -193,7 +193,7 @@ The differences from [`String.replace`]((https://developer.mozilla.org/en-US/doc
 ### s.replaceAll( regexpOrString, substitution )
 
 Same as `s.replace`, but replace all matched strings instead of just one.
-If `substitution` is a regex, then it must have the global (`g`) flag set, or a `TypeError` is thrown. Matches the behavior of the bultin [`String.property.replaceAll`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replaceAll).
+If `substitution` is a regex, then it must have the global (`g`) flag set, or a `TypeError` is thrown. Matches the behavior of the builtin [`String.property.replaceAll`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replaceAll).
 
 ### s.remove( start, end )
 
diff --git a/package-lock.json b/package-lock.json
index f52a3e0..e491793 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -6,7 +6,7 @@
   "packages": {
     "": {
       "name": "magic-string",
-      "version": "0.30.7",
+      "version": "0.30.8",
       "license": "MIT",
       "dependencies": {
         "@jridgewell/sourcemap-codec": "^1.4.15"
diff --git a/package.json b/package.json
index f8fc80c..e67fc29 100644
--- a/package.json
+++ b/package.json
@@ -33,6 +33,7 @@
     "changelog": "conventional-changelog -p angular -i CHANGELOG.md -s",
     "format": "prettier --single-quote --print-width 100 --use-tabs --write src/*.js src/**/*.js",
     "lint": "eslint src test && publint",
+    "lint:fix": "eslint src test --fix",
     "prepare": "npm run build",
     "prepublishOnly": "npm run lint && rm -rf dist && npm test",
     "release": "bumpp -x \"npm run changelog\" --all --commit --tag --push && npm publish",
diff --git a/src/MagicString.js b/src/MagicString.js
index 7e24e35..49c05cf 100644
--- a/src/MagicString.js
+++ b/src/MagicString.js
@@ -797,21 +797,29 @@ export default class MagicString {
 		if (searchValue.global) {
 			const matches = matchAll(searchValue, this.original);
 			matches.forEach((match) => {
-				if (match.index != null)
+				if (match.index != null) {
+					const replacement = getReplacement(match, this.original);
+					if (replacement !== match[0]) {
+						this.overwrite(
+							match.index,
+							match.index + match[0].length,
+							replacement
+						);
+					}
+				}
+			});
+		} else {
+			const match = this.original.match(searchValue);
+			if (match && match.index != null) {
+				const replacement = getReplacement(match, this.original);
+				if (replacement !== match[0]) {
 					this.overwrite(
 						match.index,
 						match.index + match[0].length,
-						getReplacement(match, this.original),
+						replacement
 					);
-			});
-		} else {
-			const match = this.original.match(searchValue);
-			if (match && match.index != null)
-				this.overwrite(
-					match.index,
-					match.index + match[0].length,
-					getReplacement(match, this.original),
-				);
+				}
+			}
 		}
 		return this;
 	}
@@ -843,7 +851,9 @@ export default class MagicString {
 			index !== -1;
 			index = original.indexOf(string, index + stringLength)
 		) {
-			this.overwrite(index, index + stringLength, replacement);
+			const previous = original.slice(index, index + stringLength);
+			if (previous !== replacement)
+				this.overwrite(index, index + stringLength, replacement);
 		}
 
 		return this;
diff --git a/test/MagicString.js b/test/MagicString.js
index 190cab9..a7d881a 100644
--- a/test/MagicString.js
+++ b/test/MagicString.js
@@ -1758,6 +1758,25 @@ describe('MagicString', () => {
 				new MagicString(code).replace(regex, replacer).toString()
 			);
 		});
+
+		it('should ignore non-changed replacements', () => {
+			const code = 'a12bc345#$*%';
+			const matched = [];
+
+			const s = new MagicString(code);
+
+			assert.strictEqual(s.firstChunk, s.lastChunk);
+
+			s.replace(/(\d)/g, (match, $1) => {
+				matched.push($1);
+				return match;
+			});
+
+			assert.strictEqual(s.toString(), code);
+			assert.deepStrictEqual(matched, ['1', '2', '3', '4', '5']);
+
+			assert.strictEqual(s.firstChunk, s.lastChunk);
+		});
 	});
 
 	describe('replaceAll', () => {