cstamas commented on code in PR #161:
URL: https://github.com/apache/maven-resolver/pull/161#discussion_r845927801


##########
maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/collect/bf/BfDependencyCollector.java:
##########
@@ -0,0 +1,893 @@
+package org.eclipse.aether.internal.impl.collect.bf;
+
+/*
+ * 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.
+ */
+
+import javax.inject.Inject;
+import javax.inject.Named;
+import javax.inject.Singleton;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Queue;
+
+import org.eclipse.aether.DefaultRepositorySystemSession;
+import org.eclipse.aether.RepositoryException;
+import org.eclipse.aether.RepositorySystemSession;
+import org.eclipse.aether.RequestTrace;
+import org.eclipse.aether.artifact.Artifact;
+import org.eclipse.aether.artifact.ArtifactProperties;
+import org.eclipse.aether.collection.CollectRequest;
+import org.eclipse.aether.collection.CollectResult;
+import org.eclipse.aether.collection.DependencyCollectionException;
+import org.eclipse.aether.collection.DependencyGraphTransformer;
+import org.eclipse.aether.collection.DependencyManagement;
+import org.eclipse.aether.collection.DependencyManager;
+import org.eclipse.aether.collection.DependencySelector;
+import org.eclipse.aether.collection.DependencyTraverser;
+import org.eclipse.aether.collection.VersionFilter;
+import org.eclipse.aether.graph.DefaultDependencyNode;
+import org.eclipse.aether.graph.Dependency;
+import org.eclipse.aether.graph.DependencyNode;
+import org.eclipse.aether.graph.Exclusion;
+import org.eclipse.aether.impl.ArtifactDescriptorReader;
+import org.eclipse.aether.impl.RemoteRepositoryManager;
+import org.eclipse.aether.impl.VersionRangeResolver;
+import org.eclipse.aether.internal.impl.collect.CachingArtifactTypeRegistry;
+import org.eclipse.aether.internal.impl.collect.DataPool;
+import 
org.eclipse.aether.internal.impl.collect.DefaultDependencyCollectionContext;
+import org.eclipse.aether.internal.impl.collect.DefaultDependencyCycle;
+import 
org.eclipse.aether.internal.impl.collect.DefaultDependencyGraphTransformationContext;
+import org.eclipse.aether.internal.impl.collect.DefaultVersionFilterContext;
+import org.eclipse.aether.internal.impl.collect.DependencyCollectorDelegate;
+import org.eclipse.aether.repository.ArtifactRepository;
+import org.eclipse.aether.repository.RemoteRepository;
+import org.eclipse.aether.resolution.ArtifactDescriptorException;
+import org.eclipse.aether.resolution.ArtifactDescriptorRequest;
+import org.eclipse.aether.resolution.ArtifactDescriptorResult;
+import org.eclipse.aether.resolution.VersionRangeRequest;
+import org.eclipse.aether.resolution.VersionRangeResolutionException;
+import org.eclipse.aether.resolution.VersionRangeResult;
+import org.eclipse.aether.spi.locator.Service;
+import org.eclipse.aether.util.ConfigUtils;
+import org.eclipse.aether.util.graph.manager.DependencyManagerUtils;
+import org.eclipse.aether.util.graph.transformer.TransformationContextKeys;
+import org.eclipse.aether.version.Version;
+
+import static java.util.Objects.requireNonNull;
+import static 
org.eclipse.aether.internal.impl.collect.DefaultDependencyCycle.find;
+
+/**
+ * Breadth-first {@link org.eclipse.aether.impl.DependencyCollector}
+ *
+ * @since 1.8.0
+ */
+@Singleton
+@Named( BfDependencyCollector.NAME )
+public class BfDependencyCollector
+    extends DependencyCollectorDelegate implements Service
+{
+    public static final String NAME = "bf";
+
+    /**
+     * The key in the repository session's {@link 
RepositorySystemSession#getConfigProperties()
+     * configuration properties} used to store a {@link Boolean} flag 
controlling the resolver's skip mode.
+     *
+     * @since 1.8.0
+     */
+    public static final String CONFIG_PROP_USE_SKIP = 
"aether.dependencyCollector.bf.useSkip";
+
+    /**
+     * The default value for {@link #CONFIG_PROP_USE_SKIP}, {@code true}.
+     *
+     * @since 1.8.0
+     */
+    public static final boolean CONFIG_PROP_USE_SKIP_DEFAULT = true;
+
+    public BfDependencyCollector()
+    {
+        // enables default constructor
+    }
+
+    @Inject
+    BfDependencyCollector( RemoteRepositoryManager remoteRepositoryManager,
+                           ArtifactDescriptorReader artifactDescriptorReader,
+                           VersionRangeResolver versionRangeResolver )
+    {
+        super( remoteRepositoryManager, artifactDescriptorReader, 
versionRangeResolver );
+    }
+
+    @SuppressWarnings( "checkstyle:methodlength" )
+    public CollectResult collectDependencies( RepositorySystemSession session, 
CollectRequest request )
+        throws DependencyCollectionException
+    {
+        requireNonNull( session, "session cannot be null" );
+        requireNonNull( request, "request cannot be null" );
+        session = optimizeSession( session );
+
+        boolean useSkip = ConfigUtils.getBoolean(
+                session, CONFIG_PROP_USE_SKIP_DEFAULT, CONFIG_PROP_USE_SKIP
+        );
+        if ( useSkip )
+        {
+            logger.debug( "Collector skip mode enabled" );
+        }
+
+        RequestTrace trace = RequestTrace.newChild( request.getTrace(), 
request );
+
+        CollectResult result = new CollectResult( request );
+
+        DependencySelector depSelector = session.getDependencySelector();
+        DependencyManager depManager = session.getDependencyManager();
+        DependencyTraverser depTraverser = session.getDependencyTraverser();
+        VersionFilter verFilter = session.getVersionFilter();
+
+        Dependency root = request.getRoot();
+        List<RemoteRepository> repositories = request.getRepositories();
+        List<Dependency> dependencies = request.getDependencies();
+        List<Dependency> managedDependencies = 
request.getManagedDependencies();
+
+        Map<String, Object> stats = new LinkedHashMap<>();
+        long time1 = System.nanoTime();
+
+        DefaultDependencyNode node;
+        if ( root != null )
+        {
+            List<? extends Version> versions;
+            VersionRangeResult rangeResult;
+            try
+            {
+                VersionRangeRequest rangeRequest =
+                    new VersionRangeRequest( root.getArtifact(), 
request.getRepositories(),
+                                             request.getRequestContext() );
+                rangeRequest.setTrace( trace );
+                rangeResult = versionRangeResolver.resolveVersionRange( 
session, rangeRequest );
+                versions = filterVersions( root, rangeResult, verFilter, new 
DefaultVersionFilterContext( session ) );
+            }
+            catch ( VersionRangeResolutionException e )
+            {
+                result.addException( e );
+                throw new DependencyCollectionException( result, 
e.getMessage() );
+            }
+
+            Version version = versions.get( versions.size() - 1 );
+            root = root.setArtifact( root.getArtifact().setVersion( 
version.toString() ) );
+
+            ArtifactDescriptorResult descriptorResult;
+            try
+            {
+                ArtifactDescriptorRequest descriptorRequest = new 
ArtifactDescriptorRequest();
+                descriptorRequest.setArtifact( root.getArtifact() );
+                descriptorRequest.setRepositories( request.getRepositories() );
+                descriptorRequest.setRequestContext( 
request.getRequestContext() );
+                descriptorRequest.setTrace( trace );
+                if ( isLackingDescriptor( root.getArtifact() ) )
+                {
+                    descriptorResult = new ArtifactDescriptorResult( 
descriptorRequest );
+                }
+                else
+                {
+                    descriptorResult = 
descriptorReader.readArtifactDescriptor( session, descriptorRequest );
+                }
+            }
+            catch ( ArtifactDescriptorException e )
+            {
+                result.addException( e );
+                throw new DependencyCollectionException( result, 
e.getMessage() );
+            }
+
+            root = root.setArtifact( descriptorResult.getArtifact() );
+
+            if ( !session.isIgnoreArtifactDescriptorRepositories() )
+            {
+                repositories = remoteRepositoryManager.aggregateRepositories( 
session, repositories,
+                                                                              
descriptorResult.getRepositories(),
+                                                                              
true );
+            }
+            dependencies = mergeDeps( dependencies, 
descriptorResult.getDependencies() );
+            managedDependencies = mergeDeps( managedDependencies, 
descriptorResult.getManagedDependencies() );
+
+            node = new DefaultDependencyNode( root );
+            node.setRequestContext( request.getRequestContext() );
+            node.setRelocations( descriptorResult.getRelocations() );
+            node.setVersionConstraint( rangeResult.getVersionConstraint() );
+            node.setVersion( version );
+            node.setAliases( descriptorResult.getAliases() );
+            node.setRepositories( request.getRepositories() );
+        }
+        else
+        {
+            node = new DefaultDependencyNode( request.getRootArtifact() );
+            node.setRequestContext( request.getRequestContext() );
+            node.setRepositories( request.getRepositories() );
+        }
+
+        result.setRoot( node );
+
+        boolean traverse = root == null || depTraverser == null || 
depTraverser.traverseDependency( root );
+        String errorPath = null;
+        if ( traverse && !dependencies.isEmpty() )
+        {
+            DataPool pool = new DataPool( session );
+
+            DefaultDependencyCollectionContext context =
+                new DefaultDependencyCollectionContext( session, 
request.getRootArtifact(), root, managedDependencies );
+
+            DefaultVersionFilterContext versionContext = new 
DefaultVersionFilterContext( session );
+
+            Args args =
+                    new Args( session, trace, pool, context, versionContext, 
request,
+                            useSkip ? 
DependencyResolutionSkipper.defaultSkipper()
+                                    : 
DependencyResolutionSkipper.neverSkipper() );
+            Results results = new Results( result, session );
+
+            DependencySelector rootDepSelector =
+                    depSelector != null ? depSelector.deriveChildSelector( 
context ) : null;
+            DependencyManager rootDepManager = depManager != null ? 
depManager.deriveChildManager( context ) : null;
+            DependencyTraverser rootDepTraverser =
+                    depTraverser != null ? depTraverser.deriveChildTraverser( 
context ) : null;
+            VersionFilter rootVerFilter = verFilter != null ? 
verFilter.deriveChildFilter( context ) : null;
+
+            List<DependencyNode> parents = Collections.singletonList( node );
+            for ( Dependency dependency : dependencies )
+            {
+                args.dependencyProcessingQueue.add(
+                        new DependencyProcessingContext( rootDepSelector, 
rootDepManager, rootDepTraverser,
+                                rootVerFilter, repositories, 
managedDependencies, parents,
+                                dependency ) );
+            }
+
+            while ( !args.dependencyProcessingQueue.isEmpty() )
+            {
+                processDependency( args, results, 
args.dependencyProcessingQueue.remove(), Collections.emptyList(),
+                        false );
+            }
+
+            args.skipper.report();
+            errorPath = results.errorPath;
+        }
+
+        long time2 = System.nanoTime();
+
+        DependencyGraphTransformer transformer = 
session.getDependencyGraphTransformer();
+        if ( transformer != null )
+        {
+            try
+            {
+                DefaultDependencyGraphTransformationContext context =
+                    new DefaultDependencyGraphTransformationContext( session );
+                context.put( TransformationContextKeys.STATS, stats );
+                result.setRoot( transformer.transformGraph( node, context ) );
+            }
+            catch ( RepositoryException e )
+            {
+                result.addException( e );
+            }
+        }
+
+        long time3 = System.nanoTime();
+        stats.put( "DefaultDependencyCollector.collectTime", time2 - time1 );
+        stats.put( "DefaultDependencyCollector.transformTime", time3 - time2 );
+        logger.debug( "Dependency collection stats {}", stats );
+
+        if ( errorPath != null )
+        {
+            throw new DependencyCollectionException( result, "Failed to 
collect dependencies at " + errorPath );
+        }
+        if ( !result.getExceptions().isEmpty() )
+        {
+            throw new DependencyCollectionException( result );
+        }
+
+        return result;
+    }
+
+    private static RepositorySystemSession optimizeSession( 
RepositorySystemSession session )
+    {
+        DefaultRepositorySystemSession optimized = new 
DefaultRepositorySystemSession( session );
+        optimized.setArtifactTypeRegistry( 
CachingArtifactTypeRegistry.newInstance( session ) );
+        return optimized;
+    }
+
+    private List<Dependency> mergeDeps( List<Dependency> dominant, 
List<Dependency> recessive )
+    {
+        List<Dependency> result;
+        if ( dominant == null || dominant.isEmpty() )
+        {
+            result = recessive;
+        }
+        else if ( recessive == null || recessive.isEmpty() )
+        {
+            result = dominant;
+        }
+        else
+        {
+            int initialCapacity = dominant.size() + recessive.size();
+            result = new ArrayList<>( initialCapacity );
+            Collection<String> ids = new HashSet<>( initialCapacity, 1.0f );
+            for ( Dependency dependency : dominant )
+            {
+                ids.add( getId( dependency.getArtifact() ) );
+                result.add( dependency );
+            }
+            for ( Dependency dependency : recessive )
+            {
+                if ( !ids.contains( getId( dependency.getArtifact() ) ) )
+                {
+                    result.add( dependency );
+                }
+            }
+        }
+        return result;
+    }
+
+    private static String getId( Artifact a )
+    {
+        return a.getGroupId() + ':' + a.getArtifactId() + ':' + 
a.getClassifier() + ':' + a.getExtension();
+    }
+
+    @SuppressWarnings( "checkstyle:parameternumber" )
+    private void processDependency( Args args, Results results, 
DependencyProcessingContext context,
+                                    List<Artifact> relocations, boolean 
disableVersionManagement )
+    {
+
+        if ( context.depSelector != null && 
!context.depSelector.selectDependency( context.dependency ) )
+        {
+            return;
+        }
+
+        PremanagedDependency preManaged =
+                PremanagedDependency.create( context.depManager, 
context.dependency, disableVersionManagement,
+                        args.premanagedState );
+        Dependency dependency = preManaged.managedDependency;
+
+        boolean noDescriptor = isLackingDescriptor( dependency.getArtifact() );
+
+        boolean traverse =
+                !noDescriptor && ( context.depTraverser == null || 
context.depTraverser.traverseDependency(
+                        dependency ) );
+
+        List<? extends Version> versions;
+        VersionRangeResult rangeResult;
+        try
+        {
+            VersionRangeRequest rangeRequest = createVersionRangeRequest( 
args, context.repositories, dependency );
+
+            rangeResult = cachedResolveRangeResult( rangeRequest, args.pool, 
args.session );
+
+            versions = filterVersions( dependency, rangeResult, 
context.verFilter, args.versionContext );
+        }
+        catch ( VersionRangeResolutionException e )
+        {
+            results.addException( dependency, e, context.parents );
+            return;
+        }
+
+        //Resolve newer version first to maximize benefits of skipper
+        Collections.reverse( versions );
+        for ( Version version : versions )
+        {
+            Artifact originalArtifact = dependency.getArtifact().setVersion( 
version.toString() );
+            Dependency d = dependency.setArtifact( originalArtifact );
+
+            ArtifactDescriptorRequest descriptorRequest =
+                    createArtifactDescriptorRequest( args, 
context.repositories, d );
+
+            final ArtifactDescriptorResult descriptorResult =
+                    noDescriptor
+                            ? new ArtifactDescriptorResult( descriptorRequest )
+                            : resolveCachedArtifactDescriptor( args.pool, 
descriptorRequest, args.session,
+                                    context.withDependency( d ), results );
+
+            if ( descriptorResult != null )
+            {
+                d = d.setArtifact( descriptorResult.getArtifact() );
+
+                int cycleEntry = find( context.parents, d.getArtifact() );
+                if ( cycleEntry >= 0 )
+                {
+                    results.addCycle( context.parents, cycleEntry, d );
+                    DependencyNode cycleNode = context.parents.get( cycleEntry 
);
+                    if ( cycleNode.getDependency() != null )
+                    {
+                        DefaultDependencyNode child =
+                                createDependencyNode( relocations, preManaged, 
rangeResult, version, d,
+                                        descriptorResult, cycleNode );
+                        context.getParent().getChildren().add( child );
+                        continue;
+                    }
+                }
+
+                if ( !descriptorResult.getRelocations().isEmpty() )
+                {
+                    boolean disableVersionManagementSubsequently =
+                        originalArtifact.getGroupId().equals( 
d.getArtifact().getGroupId() )
+                            && originalArtifact.getArtifactId().equals( 
d.getArtifact().getArtifactId() );
+
+                    processDependency( args, results, context.withDependency( 
d ), descriptorResult.getRelocations(),
+                            disableVersionManagementSubsequently );
+                    return;
+                }
+                else
+                {
+                    d = args.pool.intern( d.setArtifact( args.pool.intern( 
d.getArtifact() ) ) );
+
+                    List<RemoteRepository> repos =
+                        getRemoteRepositories( rangeResult.getRepository( 
version ), context.repositories );
+
+                    DefaultDependencyNode child =
+                        createDependencyNode( relocations, preManaged, 
rangeResult, version, d,
+                                              descriptorResult.getAliases(), 
repos, args.request.getRequestContext() );
+
+                    context.getParent().getChildren().add( child );
+
+                    boolean recurse = traverse && 
!descriptorResult.getDependencies().isEmpty();
+                    if ( recurse )
+                    {
+                        doRecurse( args, context.withDependency( d ), 
descriptorResult, child );
+                    }
+                }
+            }
+            else
+            {
+                List<RemoteRepository> repos =
+                    getRemoteRepositories( rangeResult.getRepository( version 
), context.repositories );
+                DefaultDependencyNode child =
+                    createDependencyNode( relocations, preManaged, 
rangeResult, version, d, null, repos,
+                                          args.request.getRequestContext() );
+                context.getParent().getChildren().add( child );
+            }
+        }
+    }
+
+    @SuppressWarnings( "checkstyle:parameternumber" )
+    private void doRecurse( Args args, DependencyProcessingContext 
parentContext,
+                            ArtifactDescriptorResult descriptorResult, 
DefaultDependencyNode child )
+    {
+        DefaultDependencyCollectionContext context = args.collectionContext;
+        context.set( parentContext.dependency, 
descriptorResult.getManagedDependencies() );
+
+        DependencySelector childSelector =
+                parentContext.depSelector != null ? 
parentContext.depSelector.deriveChildSelector( context ) : null;
+        DependencyManager childManager =
+                parentContext.depManager != null ? 
parentContext.depManager.deriveChildManager( context ) : null;
+        DependencyTraverser childTraverser =
+                parentContext.depTraverser != null ? 
parentContext.depTraverser.deriveChildTraverser( context ) : null;
+        VersionFilter childFilter =
+                parentContext.verFilter != null ? 
parentContext.verFilter.deriveChildFilter( context ) : null;
+
+        final List<RemoteRepository> childRepos =
+                args.ignoreRepos
+                        ? parentContext.repositories
+                        : remoteRepositoryManager.aggregateRepositories( 
args.session, parentContext.repositories,
+                        descriptorResult.getRepositories(), true );
+
+        Object key =
+                args.pool.toKey( parentContext.dependency.getArtifact(), 
childRepos, childSelector, childManager,
+                        childTraverser, childFilter );
+
+        List<DependencyNode> children = args.pool.getChildren( key );
+        if ( children == null )
+        {
+            boolean skipResolution = args.skipper.skipResolution( child, 
parentContext.parents );
+            if ( !skipResolution )
+            {
+                List<DependencyNode> parents = new ArrayList<>( 
parentContext.parents.size() + 1 );
+                parents.addAll( parentContext.parents );
+                parents.add( child );
+                for ( Dependency dependency : 
descriptorResult.getDependencies() )
+                {
+                    args.dependencyProcessingQueue.add(
+                            new DependencyProcessingContext( childSelector, 
childManager, childTraverser, childFilter,
+                                    childRepos, 
descriptorResult.getManagedDependencies(), parents, dependency ) );
+                }
+                args.pool.putChildren( key, child.getChildren() );
+                args.skipper.cache( child, parents );
+            }
+        }
+        else
+        {
+            child.setChildren( children );
+        }
+    }
+
+    private ArtifactDescriptorResult resolveCachedArtifactDescriptor( DataPool 
pool,
+                                                                      
ArtifactDescriptorRequest descriptorRequest,
+                                                                      
RepositorySystemSession session,
+                                                                      
DependencyProcessingContext context,
+                                                                      Results 
results )
+    {
+        Object key = pool.toKey( descriptorRequest );
+        ArtifactDescriptorResult descriptorResult = pool.getDescriptor( key, 
descriptorRequest );
+        if ( descriptorResult == null )
+        {
+            try
+            {
+                descriptorResult = descriptorReader.readArtifactDescriptor( 
session, descriptorRequest );
+                pool.putDescriptor( key, descriptorResult );
+            }
+            catch ( ArtifactDescriptorException e )
+            {
+                results.addException( context.dependency, e, context.parents );
+                pool.putDescriptor( key, e );
+                return null;
+            }
+
+        }
+        else if ( descriptorResult == DataPool.NO_DESCRIPTOR )
+        {
+            return null;
+        }
+
+        return descriptorResult;
+    }
+
+    @SuppressWarnings( "checkstyle:parameternumber" )
+    private static DefaultDependencyNode createDependencyNode( List<Artifact> 
relocations,
+                                                               
PremanagedDependency preManaged,
+                                                               
VersionRangeResult rangeResult, Version version,
+                                                               Dependency d, 
Collection<Artifact> aliases,
+                                                               
List<RemoteRepository> repos, String requestContext )
+    {
+        DefaultDependencyNode child = new DefaultDependencyNode( d );
+        preManaged.applyTo( child );
+        child.setRelocations( relocations );
+        child.setVersionConstraint( rangeResult.getVersionConstraint() );
+        child.setVersion( version );
+        child.setAliases( aliases );
+        child.setRepositories( repos );
+        child.setRequestContext( requestContext );
+        return child;
+    }
+
+    private static DefaultDependencyNode createDependencyNode( List<Artifact> 
relocations,
+                                                               
PremanagedDependency preManaged,
+                                                               
VersionRangeResult rangeResult, Version version,
+                                                               Dependency d, 
ArtifactDescriptorResult descriptorResult,
+                                                               DependencyNode 
cycleNode )
+    {
+        DefaultDependencyNode child =
+            createDependencyNode( relocations, preManaged, rangeResult, 
version, d, descriptorResult.getAliases(),
+                                  cycleNode.getRepositories(), 
cycleNode.getRequestContext() );
+        child.setChildren( cycleNode.getChildren() );
+        return child;
+    }
+
+    private static ArtifactDescriptorRequest createArtifactDescriptorRequest( 
Args args,
+                                                                              
List<RemoteRepository> repositories,
+                                                                              
Dependency d )
+    {
+        ArtifactDescriptorRequest descriptorRequest = new 
ArtifactDescriptorRequest();
+        descriptorRequest.setArtifact( d.getArtifact() );
+        descriptorRequest.setRepositories( repositories );
+        descriptorRequest.setRequestContext( args.request.getRequestContext() 
);
+        descriptorRequest.setTrace( args.trace );
+        return descriptorRequest;
+    }
+
+    private static VersionRangeRequest createVersionRangeRequest( Args args, 
List<RemoteRepository> repositories,
+                                                                  Dependency 
dependency )
+    {
+        VersionRangeRequest rangeRequest = new VersionRangeRequest();
+        rangeRequest.setArtifact( dependency.getArtifact() );
+        rangeRequest.setRepositories( repositories );
+        rangeRequest.setRequestContext( args.request.getRequestContext() );
+        rangeRequest.setTrace( args.trace );
+        return rangeRequest;
+    }
+
+    private VersionRangeResult cachedResolveRangeResult( VersionRangeRequest 
rangeRequest, DataPool pool,
+                                                         
RepositorySystemSession session )
+        throws VersionRangeResolutionException
+    {
+        Object key = pool.toKey( rangeRequest );
+        VersionRangeResult rangeResult = pool.getConstraint( key, rangeRequest 
);
+        if ( rangeResult == null )
+        {
+            rangeResult = versionRangeResolver.resolveVersionRange( session, 
rangeRequest );
+            pool.putConstraint( key, rangeResult );
+        }
+        return rangeResult;
+    }
+
+    private static boolean isLackingDescriptor( Artifact artifact )
+    {
+        return artifact.getProperty( ArtifactProperties.LOCAL_PATH, null ) != 
null;
+    }
+
+    private static List<RemoteRepository> getRemoteRepositories( 
ArtifactRepository repository,
+                                                                 
List<RemoteRepository> repositories )
+    {
+        if ( repository instanceof RemoteRepository )
+        {
+            return Collections.singletonList( (RemoteRepository) repository );
+        }
+        if ( repository != null )
+        {
+            return Collections.emptyList();
+        }
+        return repositories;
+    }
+
+    private static List<? extends Version> filterVersions( Dependency 
dependency, VersionRangeResult rangeResult,
+                                                           VersionFilter 
verFilter,
+                                                           
DefaultVersionFilterContext verContext )
+        throws VersionRangeResolutionException
+    {
+        if ( rangeResult.getVersions().isEmpty() )
+        {
+            throw new VersionRangeResolutionException( rangeResult,
+                                                       "No versions available 
for " + dependency.getArtifact()
+                                                           + " within 
specified range" );
+        }
+
+        List<? extends Version> versions;
+        if ( verFilter != null && 
rangeResult.getVersionConstraint().getRange() != null )
+        {
+            verContext.set( dependency, rangeResult );
+            try
+            {
+                verFilter.filterVersions( verContext );
+            }
+            catch ( RepositoryException e )
+            {
+                throw new VersionRangeResolutionException( rangeResult,
+                                                           "Failed to filter 
versions for " + dependency.getArtifact()
+                                                               + ": " + 
e.getMessage(), e );

Review Comment:
   am unsure is changing log/exception output in scope of this PR



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