perf(vscode): replace fast-diff with whitespace check

Author: johnsoncodehk

extensions/vscode/lib/rangeFormatting.ts

@@ -1,5 +1,4 @@
 import type * as vscode from 'vscode';
-import diff = require('fast-diff');
 
 /** for test unit */
 export type FormatableTextDocument = Pick<vscode.TextDocument, 'getText' | 'offsetAt' | 'positionAt'>;
@@ -61,72 +60,41 @@ function getTrimmedNewText(
 		return;
 	}
 
-	const map = createOffsetMap(oldText, edit.newText);
-	const newStart = map[overlapStart];
-	const newEnd = map[overlapEnd];
-	return {
-		start: editStart + overlapStart,
-		end: editStart + overlapEnd,
-		newText: edit.newText.slice(newStart, newEnd),
-	};
-}
+	let oldTextIndex = 0;
+	let newTextIndex = 0;
+	let newStart = overlapStart;
+	let newEnd = overlapEnd;
 
-function createOffsetMap(oldText: string, newText: string) {
-	const length = oldText.length;
-	const map = new Array<number>(length + 1);
-	let oldIndex = 0;
-	let newIndex = 0;
-	map[0] = 0;
-
-	for (const [op, text] of diff(oldText, newText)) {
-		if (op === diff.EQUAL) {
-			for (let i = 0; i < text.length; i++) {
-				oldIndex++;
-				newIndex++;
-				map[oldIndex] = newIndex;
-			}
-		}
-		else if (op === diff.DELETE) {
-			for (let i = 0; i < text.length; i++) {
-				oldIndex++;
-				map[oldIndex] = Number.NaN;
-			}
+	while (true) {
+		if (oldTextIndex === overlapStart) {
+			newStart = newTextIndex;
 		}
-		else {
-			newIndex += text.length;
+		if (oldTextIndex === overlapEnd) {
+			newEnd = newTextIndex;
+			break;
 		}
-	}
-
-	map[length] = newIndex;
-
-	let lastDefinedIndex = 0;
-	for (let i = 1; i <= length; i++) {
-		if (map[i] === undefined || Number.isNaN(map[i])) {
+		const oldCharCode = oldText.charCodeAt(oldTextIndex);
+		const newCharCode = edit.newText.charCodeAt(newTextIndex);
+		if (oldCharCode === newCharCode || (!isWhitespaceChar(oldCharCode) && !isWhitespaceChar(newCharCode))) {
+			oldTextIndex++;
+			newTextIndex++;
 			continue;
 		}
-		interpolate(map, lastDefinedIndex, i);
-		lastDefinedIndex = i;
-	}
-	if (lastDefinedIndex < length) {
-		interpolate(map, lastDefinedIndex, length);
+		if (isWhitespaceChar(oldCharCode)) {
+			oldTextIndex++;
+		}
+		if (isWhitespaceChar(newCharCode)) {
+			newTextIndex++;
+		}
 	}
 
-	return map;
+	return {
+		start: editStart + overlapStart,
+		end: editStart + overlapEnd,
+		newText: edit.newText.slice(newStart, newEnd),
+	};
 }
 
-function interpolate(map: number[], startIndex: number, endIndex: number) {
-	const startValue = map[startIndex] ?? 0;
-	const endValue = map[endIndex] ?? startValue;
-	const gap = endIndex - startIndex;
-	if (gap <= 1) {
-		return;
-	}
-	const delta = (endValue - startValue) / gap;
-	for (let i = 1; i < gap; i++) {
-		const index = startIndex + i;
-		if (map[index] !== undefined && !Number.isNaN(map[index])) {
-			continue;
-		}
-		map[index] = Math.floor(startValue + delta * i);
-	}
+function isWhitespaceChar(charCode: number) {
+	return charCode === 32 || charCode === 9 || charCode === 10 || charCode === 13;
 }

extensions/vscode/package.json

@@ -490,7 +490,6 @@
 		"@vue/language-core": "3.1.8",
 		"@vue/language-server": "3.1.8",
 		"@vue/typescript-plugin": "3.1.8",
-		"fast-diff": "^1.3.0",
 		"laplacenoma": "^0.0.3",
 		"reactive-vscode": "^0.2.9",
 		"rolldown": "1.0.0-beta.8",

extensions/vscode/tests/rangeFormatting.spec.ts

@@ -30,7 +30,7 @@ describe('provideDocumentRangeFormattingEdits', () => {
 			createTextEdit(
 				selection.start.character - 1,
 				selection.end.character,
-				`  <div>
+				`\n  <div>
     <div>2</div>
   </div>`,
 			),