search: fix faulty replacements in crlf files with lf regex

Fixes #165700

Regex normalization was actually working fine (finally). The issue was
JS code was matching again to do the replacement. If the original regex
only was written for LF, but the file was CRLF, VS Code did not attempt
to normalize line feeds until it tried to pull the surrounding content
as well as a 'last resort'.

If the surrounding content included a match before the intended one,
then that would be used instead, resulting in the bug.

PR does a small style change to add early returns to avoid nesting.

src/vs/workbench/contrib/search/common/searchModel.ts

@@ -109,25 +109,37 @@ export class Match {
 
 		const fullMatchText = this.fullMatchText();
 		let replaceString = searchModel.replacePattern.getReplaceString(fullMatchText, searchModel.preserveCase);
+		if (replaceString !== null) {
+			return replaceString;
+		}
 
-		// If match string is not matching then regex pattern has a lookahead expression
-		if (replaceString === null) {
-			const fullMatchTextWithSurroundingContent = this.fullMatchText(true);
-			replaceString = searchModel.replacePattern.getReplaceString(fullMatchTextWithSurroundingContent, searchModel.preserveCase);
-
-			// Search/find normalize line endings - check whether \r prevents regex from matching
-			if (replaceString === null) {
-				const fullMatchTextWithoutCR = fullMatchTextWithSurroundingContent.replace(/\r\n/g, '\n');
-				replaceString = searchModel.replacePattern.getReplaceString(fullMatchTextWithoutCR, searchModel.preserveCase);
+		// Search/find normalize line endings - check whether \r prevents regex from matching
+		const fullMatchTextWithoutCR = fullMatchText.replace(/\r\n/g, '\n');
+		if (fullMatchTextWithoutCR !== fullMatchText) {
+			replaceString = searchModel.replacePattern.getReplaceString(fullMatchTextWithoutCR, searchModel.preserveCase);
+			if (replaceString !== null) {
+				return replaceString;
 			}
 		}
 
-		// Match string is still not matching. Could be unsupported matches (multi-line).
-		if (replaceString === null) {
-			replaceString = searchModel.replacePattern.pattern;
+		// If match string is not matching then regex pattern has a lookahead expression
+		const contextMatchTextWithSurroundingContent = this.fullMatchText(true);
+		replaceString = searchModel.replacePattern.getReplaceString(contextMatchTextWithSurroundingContent, searchModel.preserveCase);
+		if (replaceString !== null) {
+			return replaceString;
+		}
+
+		// Search/find normalize line endings, this time in full context
+		const contextMatchTextWithoutCR = contextMatchTextWithSurroundingContent.replace(/\r\n/g, '\n');
+		if (contextMatchTextWithoutCR !== contextMatchTextWithSurroundingContent) {
+			replaceString = searchModel.replacePattern.getReplaceString(contextMatchTextWithoutCR, searchModel.preserveCase);
+			if (replaceString !== null) {
+				return replaceString;
+			}
 		}
 
-		return replaceString;
+		// Match string is still not matching. Could be unsupported matches (multi-line).
+		return searchModel.replacePattern.pattern;
 	}
 
 	fullMatchText(includeSurrounding = false): string {