Make rootDirectory really 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/RootLocator.java

@@ -26,7 +26,7 @@ import org.apache.maven.api.annotations.Nonnull;
 /**
  * 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.

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.PluginManagementInjector;
 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 @@ public class DefaultModelBuilder implements ModelBuilder {
             top = top.toAbsolutePath().normalize();
 
             // Obtain the root directory, resolving it if necessary
-            Path rootDirectory;
+            Path rootDirectory = session.getRootDirectory();
-            try {
-                rootDirectory = session.getRootDirectory();
-            } catch (IllegalStateException e) {
-                rootDirectory = session.getService(RootLocator.class).findMandatoryRoot(top);
-            }
 
             // Locate and normalize the root POM if it exists, fallback to top otherwise
             Path root = modelProcessor.locateExistingPom(rootDirectory);
@@ -1177,19 +1171,11 @@ public class DefaultModelBuilder implements ModelBuilder {
         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 @@ public class DefaultModelBuilder implements ModelBuilder {
                 return null;
             }
 
-            Path rootDirectory;
+            Path rootDirectory = request.getSession().getRootDirectory();
-            try {
-                rootDirectory = request.getSession().getRootDirectory();
-            } catch (IllegalStateException e) {
-                rootDirectory = null;
-            }
             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

@@ -53,10 +53,10 @@ public class DefaultRootLocator implements RootLocator {
         while (rootDirectory != null && !isRootDirectory(rootDirectory)) {
             rootDirectory = rootDirectory.getParent();
         }
-        Optional<Path> rdf = getRootDirectoryFallback();
+        Optional<Path> rdf = getMultiModuleProjectDirectory();
         if (rootDirectory == null) {
-            rootDirectory = rdf.orElseThrow(() -> new IllegalStateException(getNoRootMessage()));
             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");
@@ -75,7 +75,7 @@ public class DefaultRootLocator implements RootLocator {
         return false;
     }
 
-    protected Optional<Path> getRootDirectoryFallback() {
+    protected Optional<Path> getMultiModuleProjectDirectory() {
         String mmpd = System.getProperty("maven.multiModuleProjectDirectory");
         if (mmpd != null) {
             return Optional.of(Paths.get(mmpd));

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

@@ -52,6 +52,7 @@ import org.apache.maven.api.services.PackagingRegistry;
 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 class ApiRunner {
 
         @Override
         public Path getTopDirectory() {
-            return null;
+            return Paths.get("");
         }
 
         @Override
         public Path getRootDirectory() {
-            throw new IllegalStateException();
+            return getService(RootLocator.class).findMandatoryRoot(getTopDirectory());
         }
 
         @Override

maven-compat/src/test/java/org/apache/maven/AbstractCoreMavenComponentTestCase.java

@@ -90,7 +90,7 @@ public abstract class AbstractCoreMavenComponentTestCase {
     }
 
     protected MavenExecutionRequest createMavenExecutionRequest(File pom) throws Exception {
-        MavenExecutionRequest request = new DefaultMavenExecutionRequest()
+        MavenExecutionRequest request = new DefaultMavenExecutionRequest(true)
                 .setPom(pom)
                 .setProjectPresent(true)
                 .setShowErrors(true)
@@ -102,6 +102,7 @@ public abstract class AbstractCoreMavenComponentTestCase {
 
         if (pom != null) {
             request.setMultiModuleProjectDirectory(pom.getParentFile());
+            request.setRootDirectory(pom.getParentFile().toPath());
         }
 
         return request;

maven-compat/src/test/java/org/apache/maven/project/AbstractMavenProjectTestCase.java

@@ -161,7 +161,7 @@ public abstract class AbstractMavenProjectTestCase {
         session.setLocalRepositoryManager(new LegacyLocalRepositoryManager(localRepo));
         request.setRepositorySession(session);
 
-        DefaultMavenExecutionRequest mavenExecutionRequest = new DefaultMavenExecutionRequest();
+        DefaultMavenExecutionRequest mavenExecutionRequest = new DefaultMavenExecutionRequest(true);
         MavenSession msession =
                 new MavenSession(getContainer(), session, mavenExecutionRequest, new DefaultMavenExecutionResult());
         DefaultSession iSession = new DefaultSession(

maven-compat/src/test/java/org/apache/maven/repository/LegacyRepositorySystemTest.java

@@ -123,7 +123,7 @@ class LegacyRepositorySystemTest {
                 new LocalRepository(request.getLocalRepository().getBasedir());
         session.setLocalRepositoryManager(new SimpleLocalRepositoryManagerFactory().newInstance(session, localRepo));
         LegacySupport legacySupport = container.lookup(LegacySupport.class);
-        DefaultMavenExecutionRequest mavenExecutionRequest = new DefaultMavenExecutionRequest();
+        DefaultMavenExecutionRequest mavenExecutionRequest = new DefaultMavenExecutionRequest(true);
         MavenSession mavenSession =
                 new MavenSession(container, session, mavenExecutionRequest, new DefaultMavenExecutionResult());
         legacySupport.setSession(mavenSession);

maven-core/src/main/java/org/apache/maven/execution/DefaultMavenExecutionRequest.java

@@ -20,6 +20,7 @@ package org.apache.maven.execution;
 
 import java.io.File;
 import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.HashMap;
@@ -172,6 +173,12 @@ public class DefaultMavenExecutionRequest implements MavenExecutionRequest {
 
     public DefaultMavenExecutionRequest() {}
 
+    public DefaultMavenExecutionRequest(boolean withDefaultRoot) {
+        if (withDefaultRoot) {
+            setRootDirectory(Paths.get("").toAbsolutePath());
+        }
+    }
+
     public static MavenExecutionRequest copy(MavenExecutionRequest original) {
         DefaultMavenExecutionRequest copy = new DefaultMavenExecutionRequest();
         copy.setLocalRepository(original.getLocalRepository());

maven-core/src/test/java/org/apache/maven/AbstractCoreMavenComponentTestCase.java

@@ -21,6 +21,7 @@ package org.apache.maven;
 import javax.inject.Inject;
 
 import java.io.File;
+import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
@@ -90,7 +91,8 @@ public abstract class AbstractCoreMavenComponentTestCase {
 
     protected MavenExecutionRequest createMavenExecutionRequest(File pom) throws Exception {
         MavenExecutionRequest request = new DefaultMavenExecutionRequest()
-                .setRootDirectory(pom != null ? pom.toPath().getParent() : null)
+                .setRootDirectory(
+                        pom != null ? pom.toPath().getParent() : Paths.get("").toAbsolutePath())
                 .setPom(pom)
                 .setProjectPresent(true)
                 .setShowErrors(true)

maven-core/src/test/java/org/apache/maven/MavenTestHelper.java

@@ -32,7 +32,7 @@ public class MavenTestHelper {
     public static DefaultRepositorySystemSession createSession(
             MavenRepositorySystem repositorySystem, PlexusContainer container) {
         DefaultRepositorySystemSession repoSession = new DefaultRepositorySystemSession(h -> false);
-        DefaultMavenExecutionRequest request = new DefaultMavenExecutionRequest();
+        DefaultMavenExecutionRequest request = new DefaultMavenExecutionRequest(true);
         MavenSession mavenSession = new MavenSession(repoSession, request, new DefaultMavenExecutionResult());
         DefaultSession session =
                 new DefaultSession(mavenSession, null, null, repositorySystem, new DefaultLookup(container), null);

maven-core/src/test/java/org/apache/maven/internal/impl/TestApi.java

@@ -119,7 +119,7 @@ class TestApi {
                 .get()
                 .withLocalRepositoryBaseDirectories(new File("target").toPath())
                 .build();
-        DefaultMavenExecutionRequest mer = new DefaultMavenExecutionRequest();
+        DefaultMavenExecutionRequest mer = new DefaultMavenExecutionRequest(true);
         DefaultMavenExecutionResult meres = new DefaultMavenExecutionResult();
         MavenSession ms = new MavenSession(rss, mer, meres);
         DefaultSession session = new DefaultSession(

maven-core/src/test/java/org/apache/maven/project/AbstractMavenProjectTestCase.java

@@ -164,7 +164,7 @@ public abstract class AbstractMavenProjectTestCase {
                 new DefaultSessionFactory(repoSystem, repositorySystem, new DefaultLookup(container), null);
 
         MavenSession session = new MavenSession(
-                getContainer(), repoSession, new DefaultMavenExecutionRequest(), new DefaultMavenExecutionResult());
+                getContainer(), repoSession, new DefaultMavenExecutionRequest(true), new DefaultMavenExecutionResult());
         session.setSession(defaultSessionFactory.newSession(session));
 
         DefaultSession s = new DefaultSession(session, null, null, null, null, null);