Handle specifically empty filePath, and not default FS rootDir

Author: blacelle

gradle.properties

@@ -28,4 +28,4 @@ VER_DURIAN=1.2.0
 VER_JGIT=5.13.1.202206130422-r
 VER_JUNIT=5.9.2
 VER_ASSERTJ=3.24.2
-VER_MOCKITO=4.11.0
+VER_MOCKITO=5.0.0

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016 DiffPlug
+ * Copyright 2016-2023 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -237,8 +237,14 @@ public String compute(String unix, File file) {
 					unix = LineEnding.toUnix(formatted);
 				}
 			} catch (Throwable e) {
-				String relativePath = rootDir.relativize(file.toPath()).toString();
-				exceptionPolicy.handleError(e, step, relativePath);
+				if (file.getPath().isEmpty()) {
+					// Path.relativize would fail if rootDir is an absolute path
+					exceptionPolicy.handleError(e, step, "");
+				} else {
+					// Path may be forged from a different FileSystem than Filesystem.default
+					String relativePath = rootDir.relativize(rootDir.getFileSystem().getPath(file.getPath())).toString();
+					exceptionPolicy.handleError(e, step, relativePath);
+				}
 			}
 		}
 		return unix;

testlib/build.gradle

@@ -12,6 +12,7 @@ dependencies {
 	api "com.diffplug.durian:durian-testlib:${VER_DURIAN}"
 	api "org.junit.jupiter:junit-jupiter:${VER_JUNIT}"
 	api "org.assertj:assertj-core:${VER_ASSERTJ}"
+	api "org.mockito:mockito-core:$VER_MOCKITO"
 
 	implementation "com.diffplug.durian:durian-io:${VER_DURIAN}"
 	implementation "com.diffplug.durian:durian-collect:${VER_DURIAN}"

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2022 DiffPlug
+ * Copyright 2016-2023 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,15 +15,19 @@
  */
 package com.diffplug.spotless;
 
+import java.io.File;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.FileSystems;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
 
 import com.diffplug.common.base.StandardSystemProperty;
 import com.diffplug.spotless.generic.EndWithNewlineStep;
@@ -89,4 +93,64 @@ protected Formatter create() {
 			}
 		}.testEquals();
 	}
+
+	// new File("") can be used if there is no File representing this content. It should not conflict with rootDir.relativize(...)
+	@Test
+	public void testExceptionWithEmptyPath() throws Exception {
+		LineEnding.Policy lineEndingsPolicy = LineEnding.UNIX.createPolicy();
+		Charset encoding = StandardCharsets.UTF_8;
+		FormatExceptionPolicy exceptionPolicy = FormatExceptionPolicy.failOnlyOnError();
+
+		Path rootDir = Paths.get(StandardSystemProperty.USER_DIR.value());
+
+		FormatterStep step = Mockito.mock(FormatterStep.class);
+		Mockito.when(step.getName()).thenReturn("someFailingStep");
+		Mockito.when(step.format(Mockito.anyString(), Mockito.any(File.class))).thenThrow(new IllegalArgumentException("someReason"));
+		List<FormatterStep> steps = Collections.singletonList(step);
+
+		Formatter formatter = Formatter.builder()
+				.lineEndingsPolicy(lineEndingsPolicy)
+				.encoding(encoding)
+				.rootDir(rootDir)
+				.steps(steps)
+				.exceptionPolicy(exceptionPolicy)
+				.build();
+
+		formatter.compute("someFileContent", new File(""));
+	}
+
+	// rootDir may be a path not from the default FileSystem
+	@Test
+	public void testExceptionWithRootDirIsNotFileSystem() throws Exception {
+		LineEnding.Policy lineEndingsPolicy = LineEnding.UNIX.createPolicy();
+		Charset encoding = StandardCharsets.UTF_8;
+		FormatExceptionPolicy exceptionPolicy = FormatExceptionPolicy.failOnlyOnError();
+
+		Path rootDir = Mockito.mock(Path.class);
+		Path relativized = Mockito.mock(Path.class);
+		Mockito.when(rootDir.relativize(Mockito.any(Path.class))).then(invok -> {
+			Path filePath = invok.getArgument(0);
+			if (filePath.getFileSystem() == FileSystems.getDefault()) {
+				throw new IllegalArgumentException("Can not relativize through different FileSystems");
+			}
+
+			return relativized;
+		});
+
+		FormatterStep step = Mockito.mock(FormatterStep.class);
+		Mockito.when(step.getName()).thenReturn("someFailingStep");
+		Mockito.when(step.format(Mockito.anyString(), Mockito.any(File.class))).thenThrow(new IllegalArgumentException("someReason"));
+		List<FormatterStep> steps = Collections.singletonList(step);
+
+		Formatter formatter = Formatter.builder()
+				.lineEndingsPolicy(lineEndingsPolicy)
+				.encoding(encoding)
+				.rootDir(rootDir)
+				.steps(steps)
+				.exceptionPolicy(exceptionPolicy)
+				.build();
+
+		formatter.compute("someFileContent", new File(""));
+	}
+
 }