Fix the problem that the dependency tree is different when DF and BF …

maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/collect/bf/BfDependencyCollector.java

@@ -448,9 +448,17 @@ private void processDependency( Args args, Results results, DependencyProcessing
                     context.getParent().getChildren().add( child );
 
                     boolean recurse = traverse && !descriptorResult.getDependencies().isEmpty();
+                    DependencyProcessingContext parentContext = context.withDependency( d );
                     if ( recurse )
                     {
-                        doRecurse( args, context.withDependency( d ), descriptorResult, child );
+                        doRecurse( args, parentContext, descriptorResult, child );
+                    }
+                    else if ( !args.skipper.skipResolution( child, parentContext.parents ) )
+                    {
+                        List<DependencyNode> parents = new ArrayList<>( parentContext.parents.size() + 1 );
+                        parents.addAll( parentContext.parents );
+                        parents.add( child );
+                        args.skipper.cache( child, parents );
                     }
                 }
             }

maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/collect/bf/BfDependencyCollectorTest.java

@@ -61,6 +61,11 @@
 import org.eclipse.aether.util.graph.manager.DefaultDependencyManager;
 import org.eclipse.aether.util.graph.manager.DependencyManagerUtils;
 import org.eclipse.aether.util.graph.manager.TransitiveDependencyManager;
+import org.eclipse.aether.util.graph.transformer.ConflictResolver;
+import org.eclipse.aether.util.graph.transformer.JavaScopeDeriver;
+import org.eclipse.aether.util.graph.transformer.JavaScopeSelector;
+import org.eclipse.aether.util.graph.transformer.NearestVersionSelector;
+import org.eclipse.aether.util.graph.transformer.SimpleOptionalitySelector;
 import org.eclipse.aether.util.graph.version.HighestVersionFilter;
 import org.junit.Before;
 import org.junit.Test;
@@ -576,6 +581,26 @@ public void testVersionFilter()
         assertEquals( 1, result.getRoot().getChildren().size() );
     }
 
+
+    @Test
+    public void testDescriptorDependenciesEmpty()
+            throws Exception
+    {
+        DependencyNode root = parser.parseResource("expectedSubtreeOnDescriptorDependenciesEmpty.txt");
+        Dependency dependency = root.getDependency();
+        CollectRequest request = new CollectRequest(dependency, Arrays.asList(repository));
+
+        collector.setArtifactDescriptorReader(newReader("dependencies-empty/"));
+
+        session.setDependencyGraphTransformer(new ConflictResolver(
+                new NearestVersionSelector(), new JavaScopeSelector(), new SimpleOptionalitySelector(),
+                new JavaScopeDeriver()
+        ));
+
+        CollectResult result = collector.collectDependencies(session, request);
+        assertEqualSubtree(root, result.getRoot());
+    }
+
     static class TestDependencyManager
         implements DependencyManager
     {

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_a_ver.ini

@@ -0,0 +1,4 @@
+[dependencies]
+gid:b:jar:ver
+gid:c:jar:ver
+gid:e:jar:ver

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_b_ver.ini

@@ -0,0 +1,2 @@
+[dependencies]
+gid:d:jar:1

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_c_ver.ini

@@ -0,0 +1,2 @@
+[dependencies]
+gid:d:jar:2

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_d_1.ini

@@ -0,0 +1 @@
+[dependencies]

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_d_2.ini

@@ -0,0 +1,2 @@
+[dependencies]
+gid:g:jar:1

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_e_ver.ini

@@ -0,0 +1,2 @@
+[dependencies]
+gid:f:jar:ver

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_f_ver.ini

@@ -0,0 +1,2 @@
+[dependencies]
+gid:g:jar:2

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_g_1.ini

@@ -0,0 +1,2 @@
+[dependencies]
+gid:h:jar:1

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_g_2.ini

@@ -0,0 +1,2 @@
+[dependencies]
+gid:h:jar:2

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_h_1.ini

@@ -0,0 +1 @@
+[dependencies]

maven-resolver-impl/src/test/resources/artifact-descriptions/dependencies-empty/gid_h_2.ini

@@ -0,0 +1 @@
+[dependencies]

maven-resolver-impl/src/test/resources/artifact-descriptions/expectedSubtreeOnDescriptorDependenciesEmpty.txt

@@ -0,0 +1,8 @@
+gid:a:jar:ver
++- gid:b:jar:ver compile
+|  \- gid:d:jar:1 compile
++- gid:c:jar:ver compile
+\- gid:e:jar:ver compile
+|  +- gid:f:jar:ver compile
+|  |  +- gid:g:jar:2 compile
+|  |  |  \- gid:h:jar:2 compile