Add a o.a.maven.api.services.Source#resolve method

api/maven-api-core/src/main/java/org/apache/maven/api/services/Source.java

@@ -72,4 +72,18 @@ public interface Source {
      */
     @Nonnull
     String getLocation();
+
+    /**
+     * Returns a new source identified by a relative path. Implementation <strong>MUST</strong>
+     * be able to accept <code>relative</code> parameter values that
+     * <ul>
+     * <li>use either / or \ file path separator,</li>
+     * <li>have .. parent directory references,</li>
+     * <li>point either at file or directory.</li>
+     * </ul>
+     *
+     * @param relative is the path of the requested source relative to this source
+     * @return related source or <code>null</code> if no such source
+     */
+    Source resolve(String relative);
 }

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

@@ -25,6 +25,7 @@ import javax.inject.Singleton;
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
+import java.net.URI;
 import java.nio.file.Path;
 import java.util.Collection;
 import java.util.List;
@@ -46,7 +47,7 @@ import org.apache.maven.api.services.Source;
 import org.apache.maven.artifact.DefaultArtifact;
 import org.apache.maven.artifact.repository.ArtifactRepository;
 import org.apache.maven.model.building.ModelProblem;
-import org.apache.maven.model.building.ModelSource;
+import org.apache.maven.model.building.ModelSource2;
 import org.apache.maven.project.DefaultProjectBuildingRequest;
 import org.apache.maven.project.ProjectBuildingException;
 import org.apache.maven.project.ProjectBuildingRequest;
@@ -82,17 +83,7 @@ public class DefaultProjectBuilder implements ProjectBuilder {
                 res = builder.build(path.toFile(), req);
             } else if (request.getSource().isPresent()) {
                 Source source = request.getSource().get();
-                ModelSource modelSource = new ModelSource() {
+                ModelSource2 modelSource = new SourceWrapper(source);
-                    @Override
-                    public InputStream getInputStream() throws IOException {
-                        return source.openStream();
-                    }
-
-                    @Override
-                    public String getLocation() {
-                        return source.getLocation();
-                    }
-                };
                 res = builder.build(modelSource, req);
             } else if (request.getArtifact().isPresent()) {
                 Artifact a = request.getArtifact().get();
@@ -228,4 +219,34 @@ public class DefaultProjectBuilder implements ProjectBuilder {
             throw new ProjectBuilderException("Unable to build project", e);
         }
     }
+
+    private static class SourceWrapper implements ModelSource2 {
+        private final Source source;
+
+        SourceWrapper(Source source) {
+            this.source = source;
+        }
+
+        @Override
+        public InputStream getInputStream() throws IOException {
+            return source.openStream();
+        }
+
+        @Override
+        public String getLocation() {
+            return source.getLocation();
+        }
+
+        @Override
+        public ModelSource2 getRelatedSource(String relPath) {
+            Source rel = source.resolve(relPath);
+            return rel != null ? new SourceWrapper(rel) : null;
+        }
+
+        @Override
+        public URI getLocationURI() {
+            Path path = source.getPath();
+            return path != null ? path.toUri() : URI.create(source.getLocation());
+        }
+    }
 }