Rename the sentinel and move it to Formatter.

Author: nedtwigg

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

@@ -237,7 +237,7 @@ public String compute(String unix, File file) {
 					unix = LineEnding.toUnix(formatted);
 				}
 			} catch (Throwable e) {
-				if (file == FormatterStepImpl.SENTINEL) {
+				if (file == NO_FILE_SENTINEL) {
 					exceptionPolicy.handleError(e, step, "");
 				} else {
 					// Path may be forged from a different FileSystem than Filesystem.default
@@ -289,4 +289,7 @@ public void close() {
 			}
 		}
 	}
+
+	/** This Sentinel reference may be used to  Formatter requires a File, while 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/FormatterStepImpl.java

@@ -116,11 +116,8 @@ protected String format(Integer state, String rawUnix, File file) throws Excepti
 		}
 	}
 
-	/**This Sentinel reference may be used where Formatter requires a File, while there is no actual File to format */
-	public 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/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

@@ -142,7 +142,7 @@ public void testExceptionWithSentinelNoFileOnDisk() throws Exception {
 				.exceptionPolicy(exceptionPolicy)
 				.build();
 
-		formatter.compute("someFileContent", FormatterStepImpl.SENTINEL);
+		formatter.compute("someFileContent", Formatter.NO_FILE_SENTINEL);
 	}
 
 	// rootDir may be a path not from the default FileSystem