[MSHARED-785] Make ConstantPoolParser ignore classes in unnamed package

Closes #21

src/main/java/org/apache/maven/shared/dependency/analyzer/asm/ConstantPoolParser.java

@@ -170,7 +170,13 @@ static Set<String> parseConstantPoolClassReferences( ByteBuffer buf )
         Set<String> result = new HashSet<>();
         for ( Integer aClass : classes )
         {
-            result.add( stringConstants.get( aClass ) );
+            String className = stringConstants.get( aClass );
+
+            // filter out things from unnamed package, probably a false-positive
+            if ( isImportableClass( className ) )
+            {
+                result.add( className );
+            }
         }
         return result;
     }
@@ -207,4 +213,10 @@ private static String decodeString( ByteBuffer buf )
         ( (Buffer) buf ).limit( oldLimit );
         return sb.toString();
     }
+
+    private static boolean isImportableClass( String className )
+    {
+        // without a slash, class must be in unnamed package, which can't be imported
+        return className.indexOf( '/' ) != -1;
+    }
 }

src/test/java/org/apache/maven/shared/dependency/analyzer/DefaultProjectDependencyAnalyzerTest.java

@@ -32,6 +32,7 @@
 import org.apache.maven.shared.test.plugin.RepositoryTool;
 import org.apache.maven.shared.test.plugin.TestToolsException;
 import org.codehaus.plexus.PlexusTestCase;
+import org.junit.Assume;
 
 import java.io.File;
 import java.util.Arrays;
@@ -421,6 +422,29 @@ public void testTypeUseAnnotationDependencyOnLocalVariable()
         assertEquals( expectedAnalysis, actualAnalysis );
     }
 
+    public void testUnnamedPackageClassReference()
+        throws TestToolsException, ProjectDependencyAnalyzerException
+    {
+        Assume.assumeTrue( SystemUtils.isJavaVersionAtLeast( JavaVersion.JAVA_1_8 ) );
+
+        // Only visible through constant pool analysis (supported for JDK8+)
+        compileProject( "unnamedPackageClassReference/pom.xml" );
+
+        MavenProject project = getProject( "unnamedPackageClassReference/pom.xml" );
+
+        ProjectDependencyAnalysis actualAnalysis = analyzer.analyze( project );
+
+        Artifact dnsjava = createArtifact( "dnsjava", "dnsjava", "jar", "2.1.8", "compile" );
+        // we don't use any dnsjava classes so this should show up as an unused dep
+        Set<Artifact> unusedDeclaredArtifacts = Collections.singleton( dnsjava );
+
+        ProjectDependencyAnalysis expectedAnalysis =
+            new ProjectDependencyAnalysis( new HashSet<Artifact>(), new HashSet<Artifact>(), unusedDeclaredArtifacts,
+                new HashSet<Artifact>() );
+
+        assertEquals( expectedAnalysis, actualAnalysis );
+    }
+
     // private methods --------------------------------------------------------
 
     private void compileProject( String pomPath )

src/test/resources/unnamedPackageClassReference/pom.xml

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!--
+  ~ Licensed to the Apache Software Foundation (ASF) under one
+  ~ or more contributor license agreements.  See the NOTICE file
+  ~ distributed with this work for additional information
+  ~ regarding copyright ownership.  The ASF licenses this file
+  ~ to you under the Apache License, Version 2.0 (the
+  ~ "License"); you may not use this file except in compliance
+  ~ with the License.  You may obtain a copy of the License at
+  ~
+  ~   http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing,
+  ~ software distributed under the License is distributed on an
+  ~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+  ~ KIND, either express or implied.  See the License for the
+  ~ specific language governing permissions and limitations
+  ~ under the License.
+  -->
+
+<project
+    xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
+>
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>org.apache.maven.shared.dependency-analyzer.tests</groupId>
+  <artifactId>unnamedPackageClassReference</artifactId>
+  <version>1.0</version>
+  <packaging>jar</packaging>
+
+  <dependencies>
+    <dependency>
+      <groupId>dnsjava</groupId>
+      <artifactId>dnsjava</artifactId>
+      <version>2.1.8</version>
+    </dependency>
+  </dependencies>
+</project>

src/test/resources/unnamedPackageClassReference/src/main/java/unnamedPackageClassReference/Project.java

@@ -0,0 +1,31 @@
+package unnamedPackageClassReference;
+
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+public class Project
+{
+    // dnsjava 2.1.8 includes a class called "update"
+    public static final String UPDATE = "update";
+
+    public Project()
+    {
+        // no op
+    }
+}