Support a file name field in license headers

CHANGES.md

@@ -12,6 +12,7 @@ We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (
 ## [Unreleased]
 ### Changes
 * We are now opting in to Gradle's new stable configuration cache. ([#1591](https://github.com/diffplug/spotless/pull/1591))
+* Support a file name field in license headers. ([#1605](https://github.com/diffplug/spotless/pull/1605))
 
 ## [2.36.0] - 2023-02-27
 ### Added

lib/src/main/java/com/diffplug/spotless/generic/LicenseHeaderStep.java

@@ -142,7 +142,7 @@ public FormatterStep build() {
 					throw new IllegalStateException(yearMode.toString());
 				}
 				return new Runtime(headerLazy.get(), delimiter, yearSeparator, updateYear, skipLinesMatching);
-			}, step -> step::format);
+			}, step -> FormatterFunc.needsFile(step::format));
 		}
 
 		if (contentPattern == null) {
@@ -214,6 +214,8 @@ private static class Runtime implements Serializable {
 		private final boolean updateYearWithLatest;
 		private final boolean licenseHeaderWithRange;
 
+		private static final Pattern FILENAME_PATTERN = Pattern.compile("\\$FILE");
+
 		/** The license that we'd like enforced. */
 		private Runtime(String licenseHeader, String delimiter, String yearSeparator, boolean updateYearWithLatest, @Nullable String skipLinesMatching) {
 			if (delimiter.contains("\n")) {
@@ -266,9 +268,9 @@ private static Optional<String> getYearToken(String licenseHeader) {
 		}
 
 		/** Formats the given string. */
-		private String format(String raw) {
+		private String format(String raw, File file) {
 			if (skipLinesMatching == null) {
-				return addOrUpdateLicenseHeader(raw);
+				return addOrUpdateLicenseHeader(raw, file);
 			} else {
 				String[] lines = raw.split("\n");
 				StringBuilder skippedLinesBuilder = new StringBuilder();
@@ -287,11 +289,11 @@ private String format(String raw) {
 						remainingLinesBuilder.append(line).append('\n');
 					}
 				}
-				return skippedLinesBuilder + addOrUpdateLicenseHeader(remainingLinesBuilder.toString());
+				return skippedLinesBuilder + addOrUpdateLicenseHeader(remainingLinesBuilder.toString(), file);
 			}
 		}
 
-		private String addOrUpdateLicenseHeader(String raw) {
+		private String addOrUpdateLicenseHeader(String raw, File file) {
 			Matcher contentMatcher = delimiterPattern.matcher(raw);
 			if (!contentMatcher.find()) {
 				throw new IllegalArgumentException("Unable to find delimiter regex " + delimiterPattern);
@@ -305,13 +307,14 @@ private String addOrUpdateLicenseHeader(String raw) {
 						return raw;
 					} else {
 						// otherwise we'll have to add the header
-						return yearSepOrFull + content;
+						return replaceFileName(yearSepOrFull, file) + content;
 					}
 				} else {
 					// the yes year case is a bit harder
 					int beforeYearIdx = raw.indexOf(beforeYear);
 					int afterYearIdx = raw.indexOf(afterYear, beforeYearIdx + beforeYear.length() + 1);
 
+					String header;
 					if (beforeYearIdx >= 0 && afterYearIdx >= 0 && afterYearIdx + afterYear.length() <= contentMatcher.start()) {
 						// and also ends with exactly the right header, so it's easy to parse the existing year
 						String existingYear = raw.substring(beforeYearIdx + beforeYear.length(), afterYearIdx);
@@ -323,12 +326,13 @@ private String addOrUpdateLicenseHeader(String raw) {
 								return raw;
 							}
 						}
-						return beforeYear + newYear + afterYear + content;
+						header = beforeYear + newYear + afterYear;
 					} else {
 						String newYear = calculateYearBySearching(raw.substring(0, contentMatcher.start()));
 						// at worst, we just say that it was made today
-						return beforeYear + newYear + afterYear + content;
+						header = beforeYear + newYear + afterYear;
 					}
+					return replaceFileName(header, file) + content;
 				}
 			}
 		}
@@ -421,6 +425,10 @@ private String setLicenseHeaderYearsFromGitHistory(String raw, File file) throws
 			return beforeYear + yearRange + afterYear + raw.substring(contentMatcher.start());
 		}
 
+		private String replaceFileName(String header, File file) {
+			return FILENAME_PATTERN.matcher(header).replaceAll(file.getName());
+		}
+
 		private static String parseYear(String cmd, File file) throws IOException {
 			String fullCmd = cmd + " -- " + file.getAbsolutePath();
 			ProcessBuilder builder = new ProcessBuilder().directory(file.getParentFile());

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

@@ -57,14 +57,22 @@ public static StepHarness forFormatter(Formatter formatter) {
 
 	/** Asserts that the given element is transformed as expected, and that the result is idempotent. */
 	public StepHarness test(String before, String after) {
-		String actual = formatter.compute(LineEnding.toUnix(before), new File(""));
+		return test(before, after, "");
+	}
+
+	public StepHarness test(String before, String after, String fileName) {
+		String actual = formatter.compute(LineEnding.toUnix(before), new File(fileName));
 		assertEquals(after, actual, "Step application failed");
-		return testUnaffected(after);
+		return testUnaffected(after, fileName);
 	}
 
 	/** Asserts that the given element is idempotent w.r.t the step under test. */
 	public StepHarness testUnaffected(String idempotentElement) {
-		String actual = formatter.compute(LineEnding.toUnix(idempotentElement), new File(""));
+		return testUnaffected(idempotentElement, "");
+	}
+
+	public StepHarness testUnaffected(String idempotentElement, String fileName) {
+		String actual = formatter.compute(LineEnding.toUnix(idempotentElement), new File(fileName));
 		assertEquals(idempotentElement, actual, "Step is not idempotent");
 		return this;
 	}

testlib/src/test/java/com/diffplug/spotless/generic/LicenseHeaderStepTest.java

@@ -35,6 +35,8 @@ class LicenseHeaderStepTest extends ResourceHarness {
 	private static final String package_ = "package ";
 	private static final String HEADER_WITH_$YEAR = "This is a fake license, $YEAR. ACME corp.";
 	private static final String HEADER_WITH_RANGE_TO_$YEAR = "This is a fake license with range, 2009-$YEAR. ACME corp.";
+	private static final String HEADER_WITH_$FILE = "This is a fake license, $FILE. ACME corp.";
+	private static final String HEADER_WITH_$YEAR_$FILE = "This is a fake license, $FILE, $YEAR. ACME corp.";
 
 	@Test
 	void parseExistingYear() throws Exception {
@@ -163,6 +165,16 @@ private String hasHeaderWithRangeAndWithYearTo(String toYear) throws IOException
 		return hasHeaderYear(HEADER_WITH_RANGE_TO_$YEAR, toYear);
 	}
 
+	private String hasHeaderFileName(String license, String fileName) throws IOException {
+		return header(license).replace("$FILE", fileName) + getTestResource(FILE_NO_LICENSE);
+	}
+
+	private String hasHeaderYearFileName(String license, String year, String fileName) throws IOException {
+		return header(license)
+			.replace("$YEAR", year)
+			.replace("$FILE", fileName) + getTestResource(FILE_NO_LICENSE);
+	}
+
 	private static String currentYear() {
 		return String.valueOf(YearMonth.now().getYear());
 	}
@@ -250,4 +262,22 @@ void should_preserve_year_for_license_with_address() throws Throwable {
 				hasHeader(licenceWithAddress().replace("$YEAR", "2015").replace("FooBar Inc. All", "FooBar Inc.  All")),
 				hasHeader(licenceWithAddress().replace("$YEAR", "2015")));
 	}
+
+	@Test
+	void should_apply_license_containing_filename_token() throws Exception {
+		FormatterStep step = LicenseHeaderStep.headerDelimiter(header(HEADER_WITH_$FILE), package_).build();
+		StepHarness.forStep(step)
+			.test(getTestResource(FILE_NO_LICENSE), hasHeaderFileName(HEADER_WITH_$FILE, "Test.java"), "Test.java");
+	}
+
+	@Test
+	void should_apply_license_containing_YEAR_filename_token() throws Exception {
+		FormatterStep step = LicenseHeaderStep.headerDelimiter(header(HEADER_WITH_$YEAR_$FILE), package_).build();
+		StepHarness.forStep(step)
+			.test(
+				getTestResource(FILE_NO_LICENSE),
+				hasHeaderYearFileName(HEADER_WITH_$YEAR_$FILE, currentYear(), "Test.java"),
+				"Test.java"
+			);
+	}
 }