Common filter for files not supported by LicenseHeaderStep (#285)

Extracted the filter into a shared constant which is used by all
Gradle extensions and Maven mojo.

Author: lutovich

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

@@ -27,6 +27,7 @@
 
 import com.diffplug.spotless.FormatterStep;
 import com.diffplug.spotless.LineEnding;
+import com.diffplug.spotless.SerializableFileFilter;
 
 /** Prefixes a license header before the package statement. */
 public final class LicenseHeaderStep implements Serializable {
@@ -35,6 +36,9 @@ public final class LicenseHeaderStep implements Serializable {
 	private static final String NAME = "licenseHeader";
 	private static final String DEFAULT_YEAR_DELIMITER = "-";
 
+	private static final SerializableFileFilter UNSUPPORTED_JVM_FILES_FILTER = SerializableFileFilter.skipFilesNamed(
+			"package-info.java", "package-info.groovy", "module-info.java");
+
 	private final String licenseHeader;
 	private final Pattern delimiterPattern;
 	private Pattern yearMatcherPattern;
@@ -87,6 +91,10 @@ public static String defaultYearDelimiter() {
 		return DEFAULT_YEAR_DELIMITER;
 	}
 
+	public static SerializableFileFilter unsupportedJvmFilesFilter() {
+		return UNSUPPORTED_JVM_FILES_FILTER;
+	}
+
 	/** The license that we'd like enforced. */
 	private LicenseHeaderStep(String licenseHeader, String delimiter, String yearSeparator) {
 		if (delimiter.contains("\n")) {

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

@@ -30,7 +30,6 @@
 import org.gradle.api.tasks.SourceSet;
 
 import com.diffplug.common.base.StringPrinter;
-import com.diffplug.spotless.SerializableFileFilter;
 import com.diffplug.spotless.extra.EclipseBasedStepBuilder;
 import com.diffplug.spotless.extra.groovy.GrEclipseFormatterStep;
 import com.diffplug.spotless.generic.LicenseHeaderStep;
@@ -140,7 +139,7 @@ protected void setupTask(SpotlessTask task) {
 		// ensures that it skips both. See https://github.com/diffplug/spotless/issues/1
 		steps.replaceAll(step -> {
 			if (LicenseHeaderStep.name().equals(step.getName())) {
-				return step.filterByFile(SerializableFileFilter.skipFilesNamed("package-info.java", "package-info.groovy"));
+				return step.filterByFile(LicenseHeaderStep.unsupportedJvmFilesFilter());
 			} else {
 				return step;
 			}

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

@@ -28,7 +28,6 @@
 
 import com.diffplug.common.base.StringPrinter;
 import com.diffplug.spotless.FormatterStep;
-import com.diffplug.spotless.SerializableFileFilter;
 import com.diffplug.spotless.extra.EclipseBasedStepBuilder;
 import com.diffplug.spotless.extra.java.EclipseFormatterStep;
 import com.diffplug.spotless.extra.java.EclipseJdtFormatterStep;
@@ -187,17 +186,10 @@ protected void setupTask(SpotlessTask task) {
 			}
 			target = union;
 		}
-		// LicenseHeaderStep completely blows apart package-info.java & module-info.java;
-		// this common-sense check ensures that it skips package-info.java & module-info.java.
-		//
-		// See:
-		//  - https://github.com/diffplug/spotless/issues/1
-		//  - https://github.com/diffplug/spotless/issues/270
+
 		steps.replaceAll(step -> {
 			if (LicenseHeaderStep.name().equals(step.getName())) {
-				return step.filterByFile(SerializableFileFilter.skipFilesNamed(
-						"package-info.java",
-						"module-info.java"));
+				return step.filterByFile(LicenseHeaderStep.unsupportedJvmFilesFilter());
 			} else {
 				return step;
 			}

plugin-maven/src/main/java/com/diffplug/spotless/maven/generic/LicenseHeader.java

@@ -20,16 +20,12 @@
 import org.apache.maven.plugins.annotations.Parameter;
 
 import com.diffplug.spotless.FormatterStep;
-import com.diffplug.spotless.SerializableFileFilter;
 import com.diffplug.spotless.generic.LicenseHeaderStep;
 import com.diffplug.spotless.maven.FormatterStepConfig;
 import com.diffplug.spotless.maven.FormatterStepFactory;
 
 public class LicenseHeader implements FormatterStepFactory {
 
-	private static final SerializableFileFilter UNSUPPORTED_FILES_FILTER = SerializableFileFilter.skipFilesNamed(
-			"package-info.java", "module-info.java");
-
 	@Parameter
 	private String file;
 
@@ -51,7 +47,7 @@ public final FormatterStep newFormatterStep(FormatterStepConfig config) {
 					? createStepFromFile(config, delimiterString)
 					: createStepFromContent(delimiterString);
 
-			return step.filterByFile(UNSUPPORTED_FILES_FILTER);
+			return step.filterByFile(LicenseHeaderStep.unsupportedJvmFilesFilter());
 		} else {
 			throw new IllegalArgumentException("Must specify exactly one of 'file' or 'content'.");
 		}