make importPackages("") and importClasspath(..) consistent

So far `ClassFileImporter.importPackages("")` would only return classes that returns, but not classes derived from the set classpath. The reason is that this corner case has been overlooked in `NormalizedResourceName.startsWith(..)`. I.e. if the prefix is empty, then the resource would only be included if it starts with a `/`, but resources in archives do not start with a `/`.

Signed-off-by: Peter Gafert <peter.gafert@tngtech.com>

archunit/src/main/java/com/tngtech/archunit/core/importer/NormalizedResourceName.java

@@ -38,8 +38,8 @@ boolean isStartOf(String string) {
         return string.startsWith(resourceName);
     }
 
-    public boolean startsWith(NormalizedResourceName prefix) {
-        return equals(prefix) || isAncestorPath(prefix);
+    boolean startsWith(NormalizedResourceName prefix) {
+        return prefix.resourceName.isEmpty() || equals(prefix) || isAncestorPath(prefix);
     }
 
     private boolean isAncestorPath(NormalizedResourceName prefix) {

archunit/src/test/java/com/tngtech/archunit/core/importer/ClassFileImporterSlowTest.java

@@ -4,9 +4,11 @@
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Field;
 import java.util.List;
+import java.util.Set;
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
 import com.tngtech.archunit.Slow;
 import com.tngtech.archunit.core.domain.JavaClass;
 import com.tngtech.archunit.core.domain.JavaClasses;
@@ -28,6 +30,7 @@
 import static com.tngtech.archunit.testutil.Assertions.assertThatTypes;
 import static com.tngtech.archunit.testutil.TestUtils.urlOf;
 import static java.util.jar.Attributes.Name.CLASS_PATH;
+import static java.util.stream.Collectors.toSet;
 
 @Category(Slow.class)
 public class ClassFileImporterSlowTest {
@@ -53,6 +56,22 @@ public void imports_the_classpath() {
         assertThatTypes(classes).contain(ClassFileImporter.class, getClass(), Rule.class, File.class);
     }
 
+    @Test
+    public void importing_the_default_package_equals_importing_the_classpath() {
+        Set<String> classNamesOfDefaultPackageImport = new ClassFileImporter().withImportOption(importJavaBaseOrRtAndJUnitJarAndFilesOnTheClasspath())
+                .importPackages("")
+                .stream().map(JavaClass::getName).collect(toSet());
+        Set<String> classNamesOfClasspathImport = new ClassFileImporter()
+                .importClasspath(new ImportOptions().with(importJavaBaseOrRtAndJUnitJarAndFilesOnTheClasspath()))
+                .stream().map(JavaClass::getName).collect(toSet());
+
+        Set<String> classNamesOnlyInDefaultPackageImport = Sets.difference(classNamesOfDefaultPackageImport, classNamesOfClasspathImport);
+        assertThat(classNamesOnlyInDefaultPackageImport).as("Classes only contained in default package import").isEmpty();
+
+        Set<String> classNamesOnlyInClasspathImport = Sets.difference(classNamesOfClasspathImport, classNamesOfDefaultPackageImport);
+        assertThat(classNamesOnlyInClasspathImport).as("Classes only contained in classpath import").isEmpty();
+    }
+
     @Test
     public void respects_ImportOptions_when_using_the_default_importClasspath_method() {
         JavaClasses classes = new ClassFileImporter().withImportOption(DO_NOT_INCLUDE_TESTS).importClasspath();