Align code for MavenSession top/root directory with Maven 4

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

@@ -31,6 +31,7 @@
 import org.apache.maven.artifact.repository.ArtifactRepository;
 import org.apache.maven.eventspy.internal.EventSpyDispatcher;
 import org.apache.maven.model.Profile;
+import org.apache.maven.model.root.RootLocator;
 import org.apache.maven.project.DefaultProjectBuildingRequest;
 import org.apache.maven.project.ProjectBuildingRequest;
 import org.apache.maven.properties.internal.SystemProperties;
@@ -211,7 +212,11 @@ public static MavenExecutionRequest copy(MavenExecutionRequest original) {
         copy.setBuilderId(original.getBuilderId());
 
         copy.setTopDirectory(original.getTopDirectory());
-        copy.setRootDirectory(original.getRootDirectory());
+        try {
+            copy.setRootDirectory(original.getRootDirectory());
+        } catch (IllegalStateException e) {
+            // ignore during copy
+        }
 
         return copy;
     }
@@ -1120,6 +1125,9 @@ public MavenExecutionRequest setTopDirectory(Path topDirectory) {
 
     @Override
     public Path getRootDirectory() {
+        if (rootDirectory == null) {
+            throw new IllegalStateException(RootLocator.UNABLE_TO_FIND_ROOT_PROJECT_MESSAGE);
+        }
         return rootDirectory;
     }
 

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

@@ -19,6 +19,7 @@
 package org.apache.maven.execution;
 
 import java.io.File;
+import java.nio.file.Path;
 import java.util.Arrays;
 import java.util.Date;
 import java.util.List;
@@ -170,20 +171,22 @@ public MavenExecutionResult getResult() {
      *
      * @since 3.10.0
      */
-    public File getTopDirectory() {
-        return request.getTopDirectory() != null ? request.getTopDirectory().toFile() : null;
+    public Path getTopDirectory() {
+        return request.getTopDirectory();
     }
 
     /**
-     * Returns root directory if discovered or {@code null}.
+     * Returns root directory if discovered or throws {@link IllegalStateException} if it could not be found.
      * Root directory is detected, usually by the presence of {@code .mvn} directory, and is used to discover
      * extensions and other configuration files. It usually represents the "project root" or "checkout root".
      * Root directory may be equal to top directory or some parent of it (first directory where {@code .mvn} is found).
      *
+     *  @throws IllegalStateException if the root directory could not be found
+     *
      * @since 3.10.0
      */
-    public File getRootDirectory() {
-        return request.getRootDirectory() != null ? request.getRootDirectory().toFile() : null;
+    public Path getRootDirectory() {
+        return request.getRootDirectory();
     }
 
     // Backward compat

maven-embedder/src/main/java/org/apache/maven/cli/MavenCli.java

@@ -625,7 +625,9 @@ void properties(CliRequest cliRequest) throws ExitException {
         } catch (IllegalUseOfUndefinedProperty e) {
             String message = "ERROR: Illegal use of undefined property: " + e.property;
             System.err.println(message);
-            if (cliRequest.request.getRootDirectory() == null) {
+            try {
+                cliRequest.request.getRootDirectory();
+            } catch (IllegalStateException ex) {
                 System.err.println();
                 System.err.println(RootLocator.UNABLE_TO_FIND_ROOT_PROJECT_MESSAGE);
             }
@@ -1652,10 +1654,9 @@ public Object getValue(String expression) {
                         throw new IllegalUseOfUndefinedProperty(expression);
                     }
                 } else if ("session.rootDirectory".equals(expression)) {
-                    Path rootDirectory = cliRequest.request.getRootDirectory();
-                    if (rootDirectory != null) {
-                        return rootDirectory.toString();
-                    } else {
+                    try {
+                        return cliRequest.request.getRootDirectory();
+                    } catch (IllegalStateException e) {
                         throw new IllegalUseOfUndefinedProperty(expression);
                     }
                 }