Make rootDirectory mandatory

api/maven-api-core/src/main/java/org/apache/maven/api/Session.java

@@ -158,7 +158,6 @@ public interface Session {
      * Gets the root directory of the session, which is the root directory for the top directory project.
      *
      * @return the root directory, never {@code null}
-     * @throws IllegalStateException if the root directory could not be found
      * @see #getTopDirectory()
      * @see Project#getRootDirectory()
      * @see Project#isRootProject()

maven-api-impl/src/main/java/org/apache/maven/api/services/model/RootDetector.java

@@ -0,0 +1,30 @@
+/*
+ * 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.
+ */
+package org.apache.maven.api.services.model;
+
+import java.nio.file.Path;
+
+import org.apache.maven.api.Service;
+
+/**
+ * Interface used to detect is a given directory "root directory".
+ */
+public interface RootDetector extends Service {
+    boolean isRootDirectory(Path dir);
+}

maven-api-impl/src/main/java/org/apache/maven/api/services/model/RootLocator.java

@@ -22,12 +22,11 @@
 
 import org.apache.maven.api.Service;
 import org.apache.maven.api.annotations.Nonnull;
-import org.apache.maven.api.annotations.Nullable;
 
 /**
  * Interface used to locate the root directory for a given project.
  *
- * The root locator is usually looked up from the plexus container.
+ * The root locator is usually looked up from the DI container.
  * One notable exception is the computation of the early {@code session.rootDirectory}
  * property which happens very early.  The implementation used in this case
  * will be discovered using the JDK service mechanism.
@@ -42,27 +41,10 @@ public interface RootLocator extends Service {
             + " attribute on the root project's model to identify it.";
 
     @Nonnull
-    default Path findMandatoryRoot(@Nullable Path basedir) {
-        Path rootDirectory = findRoot(basedir);
-        if (rootDirectory == null) {
-            throw new IllegalStateException(getNoRootMessage());
-        }
-        return rootDirectory;
-    }
-
-    @Nullable
-    default Path findRoot(@Nullable Path basedir) {
-        Path rootDirectory = basedir;
-        while (rootDirectory != null && !isRootDirectory(rootDirectory)) {
-            rootDirectory = rootDirectory.getParent();
-        }
-        return rootDirectory;
-    }
+    Path findMandatoryRoot(@Nonnull Path basedir);
 
     @Nonnull
     default String getNoRootMessage() {
         return UNABLE_TO_FIND_ROOT_PROJECT_MESSAGE;
     }
-
-    boolean isRootDirectory(Path dir);
 }

maven-api-impl/src/main/java/org/apache/maven/internal/impl/model/DefaultModelBuilder.java

@@ -106,7 +106,6 @@
 import org.apache.maven.api.services.model.ProfileActivationContext;
 import org.apache.maven.api.services.model.ProfileInjector;
 import org.apache.maven.api.services.model.ProfileSelector;
-import org.apache.maven.api.services.model.RootLocator;
 import org.apache.maven.api.services.xml.XmlReaderException;
 import org.apache.maven.api.services.xml.XmlReaderRequest;
 import org.apache.maven.api.spi.ModelParserException;
@@ -633,12 +632,7 @@ private void buildBuildPom() throws ModelBuilderException {
             top = top.toAbsolutePath().normalize();
 
             // Obtain the root directory, resolving it if necessary
-            Path rootDirectory;
-            try {
-                rootDirectory = session.getRootDirectory();
-            } catch (IllegalStateException e) {
-                rootDirectory = session.getService(RootLocator.class).findRoot(top);
-            }
+            Path rootDirectory = session.getRootDirectory();
 
             // Locate and normalize the root POM if it exists, fallback to top otherwise
             Path root = modelProcessor.locateExistingPom(rootDirectory);
@@ -1177,19 +1171,11 @@ Model readFileModel() throws ModelBuilderException {
         Model doReadFileModel() throws ModelBuilderException {
             ModelSource modelSource = request.getSource();
             Model model;
-            Path rootDirectory;
+            Path rootDirectory = request.getSession().getRootDirectory();
             setSource(modelSource.getLocation());
             logger.debug("Reading file model from " + modelSource.getLocation());
             try {
                 boolean strict = request.getRequestType() == ModelBuilderRequest.RequestType.BUILD_POM;
-                try {
-                    rootDirectory = request.getSession().getRootDirectory();
-                } catch (IllegalStateException ignore) {
-                    rootDirectory = modelSource.getPath();
-                    while (rootDirectory != null && !Files.isDirectory(rootDirectory)) {
-                        rootDirectory = rootDirectory.getParent();
-                    }
-                }
                 try (InputStream is = modelSource.openStream()) {
                     model = modelProcessor.read(XmlReaderRequest.builder()
                             .strict(strict)
@@ -1592,12 +1578,7 @@ private Model doLoadDependencyManagement(
                 return null;
             }
 
-            Path rootDirectory;
-            try {
-                rootDirectory = request.getSession().getRootDirectory();
-            } catch (IllegalStateException e) {
-                rootDirectory = null;
-            }
+            Path rootDirectory = request.getSession().getRootDirectory();
             if (request.getRequestType() == ModelBuilderRequest.RequestType.BUILD_POM && rootDirectory != null) {
                 Path sourcePath = importSource.getPath();
                 if (sourcePath != null && sourcePath.startsWith(rootDirectory)) {

maven-api-impl/src/main/java/org/apache/maven/internal/impl/model/rootlocator/DefaultRootLocator.java

@@ -0,0 +1,85 @@
+/*
+ * 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.
+ */
+package org.apache.maven.internal.impl.model.rootlocator;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+import java.util.ServiceLoader;
+
+import org.apache.maven.api.annotations.Nonnull;
+import org.apache.maven.api.di.Named;
+import org.apache.maven.api.services.model.RootDetector;
+import org.apache.maven.api.services.model.RootLocator;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import static java.util.Objects.requireNonNull;
+
+@Named
+public class DefaultRootLocator implements RootLocator {
+    private final Logger logger = LoggerFactory.getLogger(getClass());
+
+    private final List<RootDetector> rootDetectors;
+
+    public DefaultRootLocator() {
+        this.rootDetectors = ServiceLoader.load(RootDetector.class).stream()
+                .map(ServiceLoader.Provider::get)
+                .toList();
+    }
+
+    @Nonnull
+    public Path findMandatoryRoot(@Nonnull Path basedir) {
+        requireNonNull(basedir, "basedir is null");
+        Path rootDirectory = basedir;
+        while (rootDirectory != null && !isRootDirectory(rootDirectory)) {
+            rootDirectory = rootDirectory.getParent();
+        }
+        Optional<Path> rdf = getMultiModuleProjectDirectory();
+        if (rootDirectory == null) {
+            logger.warn(getNoRootMessage());
+            rootDirectory = rdf.orElseGet(() -> Paths.get("").toAbsolutePath());
+        } else {
+            if (rdf.isPresent() && !Objects.equals(rootDirectory, rdf.get())) {
+                logger.warn("Project root directory and multiModuleProjectDirectory are not aligned");
+            }
+        }
+        return rootDirectory;
+    }
+
+    protected boolean isRootDirectory(Path dir) {
+        requireNonNull(dir, "dir is null");
+        for (RootDetector rootDetector : rootDetectors) {
+            if (rootDetector.isRootDirectory(dir)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    protected Optional<Path> getMultiModuleProjectDirectory() {
+        String mmpd = System.getProperty("maven.multiModuleProjectDirectory");
+        if (mmpd != null) {
+            return Optional.of(Paths.get(mmpd));
+        }
+        return Optional.empty();
+    }
+}

maven-api-impl/src/main/java/org/apache/maven/internal/impl/model/rootlocator/DotMvnRootDetector.java

@@ -0,0 +1,33 @@
+/*
+ * 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.
+ */
+package org.apache.maven.internal.impl.model.rootlocator;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import org.apache.maven.api.di.Named;
+import org.apache.maven.api.services.model.RootDetector;
+
+@Named
+public class DotMvnRootDetector implements RootDetector {
+    @Override
+    public boolean isRootDirectory(Path dir) {
+        return Files.isDirectory(dir.resolve(".mvn"));
+    }
+}

maven-api-impl/src/main/java/org/apache/maven/internal/impl/model/DefaultRootLocator.java → maven-api-impl/src/main/java/org/apache/maven/internal/impl/model/rootlocator/PomXmlRootDetector.java

@@ -16,7 +16,7 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-package org.apache.maven.internal.impl.model;
+package org.apache.maven.internal.impl.model.rootlocator;
 
 import javax.xml.stream.XMLInputFactory;
 import javax.xml.stream.XMLStreamException;
@@ -27,28 +27,13 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 
-import org.apache.maven.api.annotations.Nullable;
 import org.apache.maven.api.di.Named;
-import org.apache.maven.api.services.model.RootLocator;
+import org.apache.maven.api.services.model.RootDetector;
 
 @Named
-public class DefaultRootLocator implements RootLocator {
-
-    @Override
-    @Nullable
-    public Path findRoot(Path basedir) {
-        Path rootDirectory = basedir;
-        while (rootDirectory != null && !isRootDirectory(rootDirectory)) {
-            rootDirectory = rootDirectory.getParent();
-        }
-        return rootDirectory;
-    }
-
+public class PomXmlRootDetector implements RootDetector {
     @Override
     public boolean isRootDirectory(Path dir) {
-        if (Files.isDirectory(dir.resolve(".mvn"))) {
-            return true;
-        }
         // we're too early to use the modelProcessor ...
         Path pom = dir.resolve("pom.xml");
         try (InputStream is = Files.newInputStream(pom)) {

maven-api-impl/src/main/resources/META-INF/services/org.apache.maven.api.services.model.RootDetector

@@ -0,0 +1,2 @@
+org.apache.maven.internal.impl.model.rootlocator.DotMvnRootDetector
+org.apache.maven.internal.impl.model.rootlocator.PomXmlRootDetector

maven-api-impl/src/main/resources/META-INF/services/org.apache.maven.api.services.model.RootLocator

@@ -0,0 +1 @@
+org.apache.maven.internal.impl.model.rootlocator.DefaultRootLocator

maven-api-impl/src/test/java/org/apache/maven/internal/impl/standalone/ApiRunner.java

@@ -52,6 +52,7 @@
 import org.apache.maven.api.services.RepositoryFactory;
 import org.apache.maven.api.services.SettingsBuilder;
 import org.apache.maven.api.services.TypeRegistry;
+import org.apache.maven.api.services.model.RootLocator;
 import org.apache.maven.api.settings.Settings;
 import org.apache.maven.api.spi.TypeProvider;
 import org.apache.maven.di.Injector;
@@ -153,12 +154,12 @@ public Instant getStartTime() {
 
         @Override
         public Path getTopDirectory() {
-            return null;
+            return Paths.get("");
         }
 
         @Override
         public Path getRootDirectory() {
-            throw new IllegalStateException();
+            return getService(RootLocator.class).findMandatoryRoot(getTopDirectory());
         }
 
         @Override

maven-api-impl/src/test/java/org/apache/maven/internal/impl/standalone/RepositorySystemSupplier.java

@@ -47,8 +47,8 @@
 import org.apache.maven.internal.impl.model.DefaultPluginManagementInjector;
 import org.apache.maven.internal.impl.model.DefaultProfileInjector;
 import org.apache.maven.internal.impl.model.DefaultProfileSelector;
-import org.apache.maven.internal.impl.model.DefaultRootLocator;
 import org.apache.maven.internal.impl.model.ProfileActivationFilePathInterpolator;
+import org.apache.maven.internal.impl.model.rootlocator.DefaultRootLocator;
 import org.apache.maven.internal.impl.resolver.DefaultArtifactDescriptorReader;
 import org.apache.maven.internal.impl.resolver.DefaultModelResolver;
 import org.apache.maven.internal.impl.resolver.DefaultVersionRangeResolver;

maven-cli/src/main/java/org/apache/maven/cling/invoker/BaseParser.java

@@ -31,7 +31,6 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Objects;
 import java.util.Properties;
 import java.util.ServiceLoader;
 import java.util.function.Function;
@@ -43,10 +42,10 @@
 import org.apache.maven.api.cli.ParserException;
 import org.apache.maven.api.cli.ParserRequest;
 import org.apache.maven.api.cli.extensions.CoreExtension;
+import org.apache.maven.api.services.model.RootLocator;
 import org.apache.maven.cli.CLIReportingUtils;
 import org.apache.maven.cli.internal.extension.io.CoreExtensionsStaxReader;
 import org.apache.maven.cli.props.MavenPropertiesLoader;
-import org.apache.maven.model.root.RootLocator;
 import org.apache.maven.properties.internal.EnvironmentUtils;
 import org.apache.maven.properties.internal.SystemProperties;
 
@@ -196,30 +195,10 @@ protected Path getTopDirectory(LocalContext context) throws ParserException {
     }
 
     protected Path getRootDirectory(LocalContext context) throws ParserException {
-        RootLocator rootLocator =
-                ServiceLoader.load(RootLocator.class).iterator().next();
-        Path rootDirectory = rootLocator.findRoot(requireNonNull(context.topDirectory));
-
-        // TODO: multiModuleProjectDirectory vs rootDirectory?
-        // fallback if no root? otherwise make sure they are same?
-        Path mmpd = System.getProperty("maven.multiModuleProjectDirectory") == null
-                ? null
-                : getCanonicalPath(context.cwd.resolve(requireNonNull(
-                        System.getProperty("maven.multiModuleProjectDirectory"),
-                        "maven.multiModuleProjectDirectory is not set")));
-        if (rootDirectory == null) {
-            context.parserRequest.logger().warn(rootLocator.getNoRootMessage());
-            rootDirectory = requireNonNull(
-                    mmpd, "maven.multiModuleProjectDirectory is not set and rootDirectory was not discovered");
-        } else {
-            rootDirectory = getCanonicalPath(rootDirectory);
-            if (mmpd != null && !Objects.equals(rootDirectory, mmpd)) {
-                context.parserRequest
-                        .logger()
-                        .warn("Project root directory and multiModuleProjectDirectory are not aligned");
-            }
-        }
-        return getCanonicalPath(rootDirectory);
+        return getCanonicalPath(ServiceLoader.load(RootLocator.class)
+                .iterator()
+                .next()
+                .findMandatoryRoot(requireNonNull(context.topDirectory)));
     }
 
     protected Map<String, String> populateSystemProperties(LocalContext context) throws ParserException {