Handle specifically empty filePath, and not default FS rootDir

CHANGES.md

@@ -10,6 +10,8 @@ This document is intended for Spotless developers.
 We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (starting after version `1.27.0`).
 
 ## [Unreleased]
+### Added
+* `Formatter` now has a field `public static final File NO_FILE_SENTINEL` which can be used to pass string content to a Formatter or FormatterStep when there is no actual File to format. ([#1525](https://github.com/diffplug/spotless/pull/1525))
 
 ## [2.33.0] - 2023-01-26
 ### Added

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=4.11.0

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 +237,13 @@ 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 == NO_FILE_SENTINEL) {
+					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;
@@ -284,4 +289,7 @@ public void close() {
 			}
 		}
 	}
+
+	/** This Sentinel reference may be used to pass string content to a Formatter or FormatterStep when there is no actual File to format */
+	public static final File NO_FILE_SENTINEL = new File("NO_FILE_SENTINEL");
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 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.
@@ -127,7 +127,7 @@ public String apply(String unix, File file) throws Exception {
 
 				@Override
 				public String apply(String unix) throws Exception {
-					return apply(unix, FormatterStepImpl.SENTINEL);
+					return apply(unix, Formatter.NO_FILE_SENTINEL);
 				}
 			};
 		}
@@ -156,7 +156,7 @@ default String apply(String unix, File file) throws Exception {
 
 		@Override
 		default String apply(String unix) throws Exception {
-			return apply(unix, FormatterStepImpl.SENTINEL);
+			return apply(unix, Formatter.NO_FILE_SENTINEL);
 		}
 	}
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 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.
@@ -37,8 +37,8 @@ public interface FormatterStep extends Serializable {
 	 * @param rawUnix
 	 *            the content to format, guaranteed to have unix-style newlines ('\n'); never null
 	 * @param file
-	 *            the file which {@code rawUnix} was obtained from; never null. Pass an empty file using
-	 *            {@code new File("")} if and only if no file is actually associated with {@code rawUnix}
+	 *            the file which {@code rawUnix} was obtained from; never null. Pass the reference
+	 *            {@link Formatter#NO_FILE_SENTINEL} if and only if no file is actually associated with {@code rawUnix}
 	 * @return the formatted content, guaranteed to only have unix-style newlines; may return null
 	 *         if the formatter step doesn't have any changes to make
 	 * @throws Exception if the formatter step experiences a problem

lib/src/main/java/com/diffplug/spotless/FormatterStepImpl.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.
@@ -116,11 +116,8 @@ protected String format(Integer state, String rawUnix, File file) throws Excepti
 		}
 	}
 
-	/** A dummy SENTINEL file. */
-	static final File SENTINEL = new File("");
-
 	static void checkNotSentinel(File file) {
-		if (file == SENTINEL) {
+		if (file == Formatter.NO_FILE_SENTINEL) {
 			throw new IllegalArgumentException("This step requires the underlying file. If this is a test, use StepHarnessWithFile");
 		}
 	}

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/main/java/com/diffplug/spotless/StepHarness.java

@@ -88,7 +88,7 @@ public AbstractStringAssert<?> testResourceExceptionMsg(String resourceBefore) {
 
 	public AbstractStringAssert<?> testExceptionMsg(String before) {
 		try {
-			formatter.compute(LineEnding.toUnix(before), FormatterStepImpl.SENTINEL);
+			formatter.compute(LineEnding.toUnix(before), Formatter.NO_FILE_SENTINEL);
 			throw new SecurityException("Expected exception");
 		} catch (Throwable e) {
 			if (e instanceof SecurityException) {

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 +15,20 @@
  */
 package com.diffplug.spotless;
 
+import java.io.File;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.FileSystem;
+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 +94,95 @@ protected Formatter create() {
 			}
 		}.testEquals();
 	}
+
+	// new File("") as filePath is known to fail
+	@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();
+
+		Assertions.assertThrows(IllegalArgumentException.class, () -> formatter.compute("someFileContent", new File("")));
+	}
+
+	// If there is no File actually holding the content, one may rely on Formatter.NO_FILE_ON_DISK
+	@Test
+	public void testExceptionWithSentinelNoFileOnDisk() 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", Formatter.NO_FILE_SENTINEL);
+	}
+
+	// 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);
+		FileSystem customFileSystem = Mockito.mock(FileSystem.class);
+		Mockito.when(rootDir.getFileSystem()).thenReturn(customFileSystem);
+
+		Path pathFromFile = Mockito.mock(Path.class);
+		Mockito.when(customFileSystem.getPath(Mockito.anyString())).thenReturn(pathFromFile);
+
+		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("/some/folder/some.file"));
+	}
+
 }