Support lazy evaluation of YearMode, which is required for the gradle…

… plugin to respond to `ratchetFrom` in the most natural way.

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

@@ -25,6 +25,7 @@
 import java.util.List;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.function.Supplier;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
@@ -49,15 +50,15 @@ public static LicenseHeaderStep headerDelimiter(String header, String delimiter)
 	}
 
 	public static LicenseHeaderStep headerDelimiter(ThrowingEx.Supplier<String> headerLazy, String delimiter) {
-		return new LicenseHeaderStep(headerLazy, delimiter, DEFAULT_YEAR_DELIMITER, YearMode.PRESERVE);
+		return new LicenseHeaderStep(headerLazy, delimiter, DEFAULT_YEAR_DELIMITER, () -> YearMode.PRESERVE);
 	}
 
 	final ThrowingEx.Supplier<String> headerLazy;
 	final String delimiter;
 	final String yearSeparator;
-	final YearMode yearMode;
+	final Supplier<YearMode> yearMode;
 
-	private LicenseHeaderStep(ThrowingEx.Supplier<String> headerLazy, String delimiter, String yearSeparator, YearMode yearMode) {
+	private LicenseHeaderStep(ThrowingEx.Supplier<String> headerLazy, String delimiter, String yearSeparator, Supplier<YearMode> yearMode) {
 		this.headerLazy = Objects.requireNonNull(headerLazy);
 		this.delimiter = Objects.requireNonNull(delimiter);
 		this.yearSeparator = Objects.requireNonNull(yearSeparator);
@@ -81,6 +82,10 @@ public LicenseHeaderStep withYearSeparator(String yearSeparator) {
 	}
 
 	public LicenseHeaderStep withYearMode(YearMode yearMode) {
+		return withYearModeLazy(() -> yearMode);
+	}
+
+	public LicenseHeaderStep withYearModeLazy(Supplier<YearMode> yearMode) {
 		return new LicenseHeaderStep(headerLazy, delimiter, yearSeparator, yearMode);
 	}
 
@@ -103,7 +108,7 @@ public String apply(String input) throws Exception {
 	}
 
 	public FormatterStep build() {
-		if (yearMode == YearMode.SET_FROM_GIT) {
+		if (yearMode.get() == YearMode.SET_FROM_GIT) {
 			return FormatterStep.createNeverUpToDateLazy(LicenseHeaderStep.name(), () -> {
 				boolean updateYear = false; // doesn't matter
 				Runtime step = new Runtime(headerLazy.get(), delimiter, yearSeparator, updateYear);
@@ -113,7 +118,7 @@ public FormatterStep build() {
 			return FormatterStep.createLazy(LicenseHeaderStep.name(), () -> {
 				// by default, we should update the year if the user is using ratchetFrom
 				boolean updateYear;
-				switch (yearMode) {
+				switch (yearMode.get()) {
 				case PRESERVE:
 					updateYear = false;
 					break;

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/FormatExtension.java

@@ -483,14 +483,14 @@ public LicenseHeaderConfig updateYearWithLatest(boolean updateYearWithLatest) {
 		}
 
 		FormatterStep createStep() {
-			YearMode yearMode;
-			if ("true".equals(spotless.project.findProperty(LicenseHeaderStep.FLAG_SET_LICENSE_HEADER_YEARS_FROM_GIT_HISTORY()))) {
-				yearMode = YearMode.SET_FROM_GIT;
-			} else {
-				boolean updateYear = updateYearWithLatest == null ? getRatchetFrom() != null : updateYearWithLatest;
-				yearMode = updateYear ? YearMode.UPDATE_TO_TODAY : YearMode.PRESERVE;
-			}
-			return builder.withYearMode(yearMode).build();
+			return builder.withYearModeLazy(() -> {
+				if ("true".equals(spotless.project.findProperty(LicenseHeaderStep.FLAG_SET_LICENSE_HEADER_YEARS_FROM_GIT_HISTORY()))) {
+					return YearMode.SET_FROM_GIT;
+				} else {
+					boolean updateYear = updateYearWithLatest == null ? getRatchetFrom() != null : updateYearWithLatest;
+					return updateYear ? YearMode.UPDATE_TO_TODAY : YearMode.PRESERVE;
+				}
+			}).build();
 		}
 	}
 

plugin-gradle/src/test/java/com/diffplug/gradle/spotless/LicenseHeaderTest.java

@@ -46,7 +46,7 @@ private void assertUnchanged(String year) throws IOException {
 
 	private void assertTransform(String yearBefore, String yearAfter) throws IOException {
 		setFile(TEST_JAVA).toContent("/** " + yearBefore + " */\n" + CONTENT);
-		gradleRunner().withArguments("spotlessApply", "--stacktrace").build();
+		gradleRunner().withArguments("spotlessApply", "--stacktrace").forwardOutput().build();
 		assertFile(TEST_JAVA).hasContent("/** " + yearAfter + " */\n" + CONTENT);
 	}