Speedup LineEnding.toUnix, and add a test.

Author: nedtwigg

lib/src/main/java/com/diffplug/spotless/LineEnding.java

@@ -142,14 +142,17 @@ public default boolean isUnix(File file) {
 
 	/** Returns a string with exclusively unix line endings. */
 	public static String toUnix(String input) {
-		if (input.lastIndexOf(WINDOWS.str()) > -1) {
-			return input.replace("\r", "");
-		} else if (input.lastIndexOf(MAC_CLASSIC.str()) > -1) {
-			// replace mac classic '\r' with unix line endings '\n'
-			return input.replace(MAC_CLASSIC.str(), UNIX.str());
-		} else {
-			// fastest way to detect if a string is already unix-only
+		int lastCarriageReturn = input.lastIndexOf('\r');
+		if (lastCarriageReturn == -1) {
 			return input;
+		} else {
+			if (input.lastIndexOf("\r\n") == -1) {
+				// it is MAC_CLASSIC \r
+				return input.replace('\r', '\n');
+			} else {
+				// it is WINDOWS \r\n
+				return input.replace("\r", "");
+			}
 		}
 	}
 }

testlib/src/test/java/com/diffplug/spotless/FormatterTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 DiffPlug
+ * Copyright 2016-2022 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,12 +22,20 @@
 import java.util.ArrayList;
 import java.util.List;
 
+import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
 import com.diffplug.common.base.StandardSystemProperty;
 import com.diffplug.spotless.generic.EndWithNewlineStep;
 
 class FormatterTest {
+	@Test
+	void toUnix() {
+		Assertions.assertEquals("1\n2\n3", LineEnding.toUnix("1\n2\n3"));
+		Assertions.assertEquals("1\n2\n3", LineEnding.toUnix("1\r2\r3"));
+		Assertions.assertEquals("1\n2\n3", LineEnding.toUnix("1\r\n2\r\n3"));
+	}
+
 	// Formatter normally needs to be closed, but no resources will be leaked in this special case
 	@Test
 	void equality() {