Better internal helper methods (#1334)

maven-core/src/main/java/org/apache/maven/internal/impl/AbstractSession.java

@@ -29,7 +29,6 @@ import java.util.Objects;
 import java.util.Optional;
 import java.util.WeakHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
-import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import org.apache.maven.api.Artifact;
@@ -64,6 +63,7 @@ import org.apache.maven.api.services.VersionParser;
 import org.apache.maven.artifact.repository.ArtifactRepository;
 import org.apache.maven.project.MavenProject;
 
+import static org.apache.maven.internal.impl.Utils.map;
 import static org.apache.maven.internal.impl.Utils.nonNull;
 
 public abstract class AbstractSession implements InternalSession {
@@ -102,7 +102,7 @@ public abstract class AbstractSession implements InternalSession {
     }
 
     public List<Project> getProjects(List<MavenProject> projects) {
-        return projects == null ? null : projects.stream().map(this::getProject).collect(Collectors.toList());
+        return projects == null ? null : map(projects, this::getProject);
     }
 
     public Project getProject(MavenProject project) {
@@ -110,9 +110,7 @@ public abstract class AbstractSession implements InternalSession {
     }
 
     public List<org.eclipse.aether.repository.RemoteRepository> toRepositories(List<RemoteRepository> repositories) {
-        return repositories == null
+        return repositories == null ? null : map(repositories, this::toRepository);
-                ? null
-                : repositories.stream().map(this::toRepository).collect(Collectors.toList());
     }
 
     public org.eclipse.aether.repository.RemoteRepository toRepository(RemoteRepository repository) {
@@ -134,25 +132,19 @@ public abstract class AbstractSession implements InternalSession {
     }
 
     public List<ArtifactRepository> toArtifactRepositories(List<RemoteRepository> repositories) {
-        return repositories == null
+        return repositories == null ? null : map(repositories, this::toArtifactRepository);
-                ? null
-                : repositories.stream().map(this::toArtifactRepository).collect(Collectors.toList());
     }
 
     public abstract ArtifactRepository toArtifactRepository(RemoteRepository repository);
 
     public List<org.eclipse.aether.graph.Dependency> toDependencies(Collection<DependencyCoordinate> dependencies) {
-        return dependencies == null
+        return dependencies == null ? null : map(dependencies, this::toDependency);
-                ? null
-                : dependencies.stream().map(this::toDependency).collect(Collectors.toList());
     }
 
     public abstract org.eclipse.aether.graph.Dependency toDependency(DependencyCoordinate dependency);
 
     public List<org.eclipse.aether.artifact.Artifact> toArtifacts(Collection<Artifact> artifacts) {
-        return artifacts == null
+        return artifacts == null ? null : map(artifacts, this::toArtifact);
-                ? null
-                : artifacts.stream().map(this::toArtifact).collect(Collectors.toList());
     }
 
     public org.eclipse.aether.artifact.Artifact toArtifact(Artifact artifact) {

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultArtifact.java

@@ -36,8 +36,8 @@ public class DefaultArtifact implements Artifact {
     private final String id;
 
     public DefaultArtifact(@Nonnull InternalSession session, @Nonnull org.eclipse.aether.artifact.Artifact artifact) {
-        this.session = nonNull(session, "session can not be null");
+        this.session = nonNull(session, "session");
-        this.artifact = nonNull(artifact, "artifact can not be null");
+        this.artifact = nonNull(artifact, "artifact");
         this.id = getGroupId()
                 + ':'
                 + getArtifactId()

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultArtifactCoordinate.java

@@ -35,8 +35,8 @@ public class DefaultArtifactCoordinate implements ArtifactCoordinate {
 
     public DefaultArtifactCoordinate(
             @Nonnull InternalSession session, @Nonnull org.eclipse.aether.artifact.Artifact coordinate) {
-        this.session = nonNull(session, "session can not be null");
+        this.session = nonNull(session, "session");
-        this.coordinate = nonNull(coordinate, "coordinate can not be null");
+        this.coordinate = nonNull(coordinate, "coordinate");
     }
 
     public org.eclipse.aether.artifact.Artifact getCoordinate() {

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultArtifactCoordinateFactory.java

@@ -34,7 +34,7 @@ import static org.apache.maven.internal.impl.Utils.nonNull;
 public class DefaultArtifactCoordinateFactory implements ArtifactCoordinateFactory {
     @Override
     public ArtifactCoordinate create(@Nonnull ArtifactCoordinateFactoryRequest request) {
-        nonNull(request, "request can not be null");
+        nonNull(request, "request");
         InternalSession session = InternalSession.from(request.getSession());
         ArtifactType type = null;
         if (request.getType() != null) {

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultArtifactDeployer.java

@@ -47,15 +47,15 @@ public class DefaultArtifactDeployer implements ArtifactDeployer {
 
     @Inject
     DefaultArtifactDeployer(@Nonnull RepositorySystem repositorySystem) {
-        this.repositorySystem = nonNull(repositorySystem, "repositorySystem can not be null");
+        this.repositorySystem = nonNull(repositorySystem, "repositorySystem");
     }
 
     @Override
     public void deploy(@Nonnull ArtifactDeployerRequest request) {
-        nonNull(request, "request can not be null");
+        nonNull(request, "request");
         InternalSession session = InternalSession.from(request.getSession());
-        Collection<Artifact> artifacts = nonNull(request.getArtifacts(), "request.artifacts can not be null");
+        Collection<Artifact> artifacts = nonNull(request.getArtifacts(), "request.artifacts");
-        RemoteRepository repository = nonNull(request.getRepository(), "request.repository can not be null");
+        RemoteRepository repository = nonNull(request.getRepository(), "request.repository");
         try {
             DeployRequest deployRequest = new DeployRequest()
                     .setRepository(session.toRepository(repository))

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultArtifactFactory.java

@@ -34,7 +34,7 @@ import static org.apache.maven.internal.impl.Utils.nonNull;
 public class DefaultArtifactFactory implements ArtifactFactory {
     @Override
     public Artifact create(@Nonnull ArtifactFactoryRequest request) {
-        nonNull(request, "request can not be null");
+        nonNull(request, "request");
         InternalSession session = InternalSession.from(request.getSession());
         ArtifactType type = null;
         if (request.getType() != null) {

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultArtifactInstaller.java

@@ -46,7 +46,7 @@ public class DefaultArtifactInstaller implements ArtifactInstaller {
 
     @Override
     public void install(ArtifactInstallerRequest request) throws ArtifactInstallerException, IllegalArgumentException {
-        nonNull(request, "request can not be null");
+        nonNull(request, "request");
         InternalSession session = InternalSession.from(request.getSession());
         try {
             InstallRequest installRequest =

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultArtifactResolver.java

@@ -51,13 +51,13 @@ public class DefaultArtifactResolver implements ArtifactResolver {
 
     @Inject
     DefaultArtifactResolver(@Nonnull RepositorySystem repositorySystem) {
-        this.repositorySystem = nonNull(repositorySystem, "repositorySystem can not be null");
+        this.repositorySystem = nonNull(repositorySystem, "repositorySystem");
     }
 
     @Override
     public ArtifactResolverResult resolve(ArtifactResolverRequest request)
             throws ArtifactResolverException, IllegalArgumentException {
-        nonNull(request, "request can not be null");
+        nonNull(request, "request");
         InternalSession session = InternalSession.from(request.getSession());
         try {
             Map<Artifact, Path> paths = new HashMap<>();

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultDependencyCollector.java

@@ -58,7 +58,7 @@ public class DefaultDependencyCollector implements DependencyCollector {
     @Override
     public DependencyCollectorResult collect(@Nonnull DependencyCollectorRequest request)
             throws DependencyCollectorException, IllegalArgumentException {
-        nonNull(request, "request can not be null");
+        nonNull(request, "request");
         InternalSession session = InternalSession.from(request.getSession());
 
         Artifact rootArtifact =

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultDependencyCoordinateFactory.java

@@ -21,8 +21,6 @@ package org.apache.maven.internal.impl;
 import javax.inject.Named;
 import javax.inject.Singleton;
 
-import java.util.stream.Collectors;
-
 import org.apache.maven.api.DependencyCoordinate;
 import org.apache.maven.api.Exclusion;
 import org.apache.maven.api.annotations.Nonnull;
@@ -30,6 +28,7 @@ import org.apache.maven.api.services.DependencyCoordinateFactory;
 import org.apache.maven.api.services.DependencyCoordinateFactoryRequest;
 import org.eclipse.aether.artifact.ArtifactType;
 
+import static org.apache.maven.internal.impl.Utils.map;
 import static org.apache.maven.internal.impl.Utils.nonNull;
 
 @Named
@@ -39,7 +38,7 @@ public class DefaultDependencyCoordinateFactory implements DependencyCoordinateF
     @Nonnull
     @Override
     public DependencyCoordinate create(@Nonnull DependencyCoordinateFactoryRequest request) {
-        nonNull(request, "request can not be null");
+        nonNull(request, "request");
         InternalSession session = InternalSession.from(request.getSession());
 
         ArtifactType type = null;
@@ -58,7 +57,7 @@ public class DefaultDependencyCoordinateFactory implements DependencyCoordinateF
                                 type),
                         request.getScope(),
                         request.isOptional(),
-                        request.getExclusions().stream().map(this::toExclusion).collect(Collectors.toList())));
+                        map(request.getExclusions(), this::toExclusion)));
     }
 
     private org.eclipse.aether.graph.Exclusion toExclusion(Exclusion exclusion) {

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultDependencyProperties.java

@@ -40,7 +40,7 @@ public class DefaultDependencyProperties implements DependencyProperties {
     }
 
     public DefaultDependencyProperties(@Nonnull Collection<String> flags) {
-        nonNull(flags, "null flags");
+        nonNull(flags, "flags");
         HashMap<String, String> map = new HashMap<>();
         for (String flag : flags) {
             map.put(flag, Boolean.TRUE.toString());
@@ -49,7 +49,7 @@ public class DefaultDependencyProperties implements DependencyProperties {
     }
 
     public DefaultDependencyProperties(@Nonnull Map<String, String> properties) {
-        this.properties = Collections.unmodifiableMap(nonNull(properties, "null properties"));
+        this.properties = Collections.unmodifiableMap(nonNull(properties, "properties"));
     }
 
     @Nonnull
@@ -60,7 +60,7 @@ public class DefaultDependencyProperties implements DependencyProperties {
 
     @Override
     public boolean checkFlag(@Nonnull String flag) {
-        nonNull(flag, "null flag");
+        nonNull(flag, "flag");
         return Boolean.parseBoolean(properties.getOrDefault(flag, ""));
     }
 }

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultLocalRepository.java

@@ -33,7 +33,7 @@ public class DefaultLocalRepository implements LocalRepository {
 
     @Inject
     public DefaultLocalRepository(@Nonnull org.eclipse.aether.repository.LocalRepository repository) {
-        this.repository = nonNull(repository, "repository can not be null");
+        this.repository = nonNull(repository, "repository");
     }
 
     @Nonnull

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultModelXmlFactory.java

@@ -47,7 +47,7 @@ import static org.apache.maven.internal.impl.Utils.nonNull;
 public class DefaultModelXmlFactory implements ModelXmlFactory {
     @Override
     public Model read(@Nonnull XmlReaderRequest request) throws XmlReaderException {
-        nonNull(request, "request can not be null");
+        nonNull(request, "request");
         Path path = request.getPath();
         URL url = request.getURL();
         Reader reader = request.getReader();
@@ -82,8 +82,8 @@ public class DefaultModelXmlFactory implements ModelXmlFactory {
 
     @Override
     public void write(XmlWriterRequest<Model> request) throws XmlWriterException {
-        nonNull(request, "request can not be null");
+        nonNull(request, "request");
-        Model content = nonNull(request.getContent(), "content can not be null");
+        Model content = nonNull(request.getContent(), "content");
         Path path = request.getPath();
         OutputStream outputStream = request.getOutputStream();
         Writer writer = request.getWriter();

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultProjectManager.java

@@ -49,6 +49,8 @@ import org.codehaus.plexus.PlexusContainer;
 import org.codehaus.plexus.component.repository.exception.ComponentLookupException;
 import org.eclipse.sisu.Typed;
 
+import static org.apache.maven.internal.impl.Utils.map;
+
 @Named
 @Typed
 @SessionScoped
@@ -76,10 +78,9 @@ public class DefaultProjectManager implements ProjectManager {
     @Override
     public Collection<Artifact> getAttachedArtifacts(Project project) {
         InternalSession session = ((DefaultProject) project).getSession();
-        Collection<Artifact> attached = getMavenProject(project).getAttachedArtifacts().stream()
+        Collection<Artifact> attached = map(
-                .map(RepositoryUtils::toArtifact)
+                getMavenProject(project).getAttachedArtifacts(),
-                .map(session::getArtifact)
+                a -> session.getArtifact(RepositoryUtils.toArtifact(a)));
-                .collect(Collectors.toList());
         return Collections.unmodifiableCollection(attached);
     }
 
@@ -134,10 +135,7 @@ public class DefaultProjectManager implements ProjectManager {
                     InternalSession.from(session).getMavenSession(),
                     false,
                     Collections.emptySet());
-            return artifacts.stream()
+            return map(artifacts, a -> InternalSession.from(session).getArtifact(RepositoryUtils.toArtifact(a)));
-                    .map(RepositoryUtils::toArtifact)
-                    .map(InternalSession.from(session)::getArtifact)
-                    .collect(Collectors.toList());
         } catch (LifecycleExecutionException | ComponentLookupException e) {
             throw new MavenException("Unable to resolve project dependencies", e);
         }

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultSession.java

@@ -27,7 +27,6 @@ import java.util.NoSuchElementException;
 import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Supplier;
-import java.util.stream.Collectors;
 
 import org.apache.maven.RepositoryUtils;
 import org.apache.maven.api.DependencyCoordinate;
@@ -54,6 +53,7 @@ import org.eclipse.aether.DefaultRepositorySystemSession;
 import org.eclipse.aether.RepositorySystem;
 import org.eclipse.aether.RepositorySystemSession;
 
+import static org.apache.maven.internal.impl.Utils.map;
 import static org.apache.maven.internal.impl.Utils.nonNull;
 
 public class DefaultSession extends AbstractSession {
@@ -80,10 +80,9 @@ public class DefaultSession extends AbstractSession {
         this.repositorySystem = nonNull(repositorySystem);
         this.repositories = repositories != null
                 ? repositories
-                : mavenSession.getRequest().getRemoteRepositories().stream()
+                : map(
-                        .map(RepositoryUtils::toRepo)
+                        mavenSession.getRequest().getRemoteRepositories(),
-                        .map(this::getRemoteRepository)
+                        r -> getRemoteRepository(RepositoryUtils.toRepo(r)));
-                        .collect(Collectors.toList());
         this.mavenRepositorySystem = mavenRepositorySystem;
         this.container = container;
         this.runtimeInformation = runtimeInformation;

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultSettingsXmlFactory.java

@@ -25,7 +25,6 @@ import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.Reader;
 import java.io.Writer;
-import java.util.Objects;
 
 import org.apache.maven.api.annotations.Nonnull;
 import org.apache.maven.api.services.xml.SettingsXmlFactory;
@@ -38,12 +37,14 @@ import org.apache.maven.api.settings.Settings;
 import org.apache.maven.settings.v4.SettingsStaxReader;
 import org.apache.maven.settings.v4.SettingsStaxWriter;
 
+import static org.apache.maven.internal.impl.Utils.nonNull;
+
 @Named
 @Singleton
 public class DefaultSettingsXmlFactory implements SettingsXmlFactory {
     @Override
     public Settings read(@Nonnull XmlReaderRequest request) throws XmlReaderException {
-        Objects.requireNonNull(request, "request can not be null");
+        nonNull(request, "request");
         Reader reader = request.getReader();
         InputStream inputStream = request.getInputStream();
         if (reader == null && inputStream == null) {
@@ -68,8 +69,8 @@ public class DefaultSettingsXmlFactory implements SettingsXmlFactory {
 
     @Override
     public void write(XmlWriterRequest<Settings> request) throws XmlWriterException {
-        Objects.requireNonNull(request, "request can not be null");
+        nonNull(request, "request");
-        Settings content = Objects.requireNonNull(request.getContent(), "content can not be null");
+        Settings content = nonNull(request.getContent(), "content");
         OutputStream outputStream = request.getOutputStream();
         Writer writer = request.getWriter();
         if (writer == null && outputStream == null) {

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultToolchainsXmlFactory.java

@@ -38,12 +38,14 @@ import org.apache.maven.api.toolchain.PersistedToolchains;
 import org.apache.maven.toolchain.v4.MavenToolchainsStaxReader;
 import org.apache.maven.toolchain.v4.MavenToolchainsStaxWriter;
 
+import static org.apache.maven.internal.impl.Utils.nonNull;
+
 @Named
 @Singleton
 public class DefaultToolchainsXmlFactory implements ToolchainsXmlFactory {
     @Override
     public PersistedToolchains read(@Nonnull XmlReaderRequest request) throws XmlReaderException {
-        Objects.requireNonNull(request, "request can not be null");
+        Objects.requireNonNull(request, "request");
         Reader reader = request.getReader();
         InputStream inputStream = request.getInputStream();
         if (reader == null && inputStream == null) {
@@ -68,8 +70,8 @@ public class DefaultToolchainsXmlFactory implements ToolchainsXmlFactory {
 
     @Override
     public void write(XmlWriterRequest<PersistedToolchains> request) throws XmlWriterException {
-        Objects.requireNonNull(request, "request can not be null");
+        nonNull(request, "request");
-        PersistedToolchains content = Objects.requireNonNull(request.getContent(), "content can not be null");
+        PersistedToolchains content = Objects.requireNonNull(request.getContent(), "content");
         OutputStream outputStream = request.getOutputStream();
         Writer writer = request.getWriter();
         if (writer == null && outputStream == null) {

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultType.java

@@ -36,10 +36,10 @@ public class DefaultType implements Type, ArtifactType {
     private final DependencyProperties dependencyProperties;
 
     public DefaultType(String id, String extension, String classifier, DependencyProperties dependencyProperties) {
-        nonNull(id, "null id");
+        nonNull(id, "id");
-        this.extension = nonNull(extension, "null extension");
+        this.extension = nonNull(extension, "extension");
         this.classifier = classifier;
-        nonNull(dependencyProperties, "null dependencyProperties");
+        nonNull(dependencyProperties, "dependencyProperties");
         HashMap<String, String> props = new HashMap<>(dependencyProperties.asMap());
         props.put(ArtifactProperties.TYPE, id);
         this.dependencyProperties = new DefaultDependencyProperties(props);

maven-core/src/main/java/org/apache/maven/internal/impl/DefaultTypeRegistry.java

@@ -70,7 +70,7 @@ public class DefaultTypeRegistry extends AbstractEventSpy implements TypeRegistr
     @Override
     @Nonnull
     public Type getType(String id) {
-        nonNull(id, "null id");
+        nonNull(id, "id");
         return usedTypes.computeIfAbsent(id, i -> {
             Type type = types.get(id);
             if (type == null) {

maven-core/src/main/java/org/apache/maven/internal/impl/Utils.java

@@ -18,6 +18,11 @@
  */
 package org.apache.maven.internal.impl;
 
+import java.util.Collection;
+import java.util.List;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
 class Utils {
     static <T> T nonNull(T t) {
         if (t == null) {
@@ -26,17 +31,21 @@ class Utils {
         return t;
     }
 
-    static <T> T nonNull(T t, String message) {
+    static <T> T nonNull(T t, String name) {
         if (t == null) {
-            throw new IllegalArgumentException(message);
+            throw new IllegalArgumentException(name + " cannot be null");
         }
         return t;
     }
 
-    static <T> T cast(Class<T> clazz, Object o, String message) {
+    static <T> T cast(Class<T> clazz, Object o, String name) {
         if (!clazz.isInstance(o)) {
-            throw new IllegalArgumentException(message);
+            throw new IllegalArgumentException(name + " is not an instance of " + clazz.getName());
         }
         return clazz.cast(o);
     }
+
+    static <U, V> List<V> map(Collection<U> list, Function<U, V> mapper) {
+        return list.stream().map(mapper).collect(Collectors.toList());
+    }
 }

maven-core/src/main/java/org/apache/maven/internal/impl/WrapperNode.java

@@ -38,8 +38,7 @@ class WrapperNode extends AbstractNode {
 
     @Override
     DependencyNode getDependencyNode() {
-        return Utils.cast(AbstractNode.class, delegate, "delegate is not an instance of AbstractNode")
+        return Utils.cast(AbstractNode.class, delegate, "delegate").getDependencyNode();
-                .getDependencyNode();
     }
 
     @Override