Make POM and basedire required on the project

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

@@ -124,26 +124,28 @@ default Build getBuild() {
 
     /**
      * Returns the path to the pom file for this project.
-     * A project is usually read from the file system and this will point to
-     * the file.  In some cases, a transient project can be created which
-     * will not point to an actual pom file.
+     * A project is usually read from a file named {@code pom.xml},
+     * which contains the {@linkplain #getModel() model} in an XML form.
+     * When a custom {@link org.apache.maven.api.spi.ModelParser} is used,
+     * the path may point to a non XML file.
+     * <p>
+     * The POM path is also used to define the {@linkplain #getBasedir() base directory}
+     * of the project.
+     *
      * @return the path of the pom
+     * @see #getBasedir()
      */
     @Nonnull
-    Optional<Path> getPomPath();
+    Path getPomPath();
 
     /**
-     * Returns the project base directory.
-     */
-    @Nonnull
-    Optional<Path> getBasedir();
-
-    /**
-     * Enforces presence of the project base directory and returns it.
+     * Returns the project's base directory.
+     *
+     * @see #getPomPath()
      */
     @Nonnull
-    default Path requireBasedir() {
-        return getBasedir().orElseThrow(() -> new IllegalStateException("Project basedir not given"));
+    default Path getBasedir() {
+        return getPomPath().getParent();
     }
 
     /**

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

@@ -97,18 +97,9 @@ public Model getModel() {
 
     @Nonnull
     @Override
-    public Optional<Path> getPomPath() {
+    public Path getPomPath() {
         File file = project.getFile();
-        return Optional.ofNullable(file).map(File::toPath);
-    }
-
-    @Override
-    public Optional<Path> getBasedir() {
-        File basedir = project.getBasedir();
-        if (basedir == null) {
-            return Optional.empty();
-        }
-        return Optional.of(basedir.toPath());
+        return file.toPath();
     }
 
     @Nonnull
@@ -134,13 +125,12 @@ public boolean isExecutionRoot() {
 
     @Override
     public boolean isTopProject() {
-        return getBasedir().isPresent()
-                && getBasedir().get().equals(getSession().getTopDirectory());
+        return getBasedir().equals(getSession().getTopDirectory());
     }
 
     @Override
     public boolean isRootProject() {
-        return getBasedir().isPresent() && getBasedir().get().equals(getRootDirectory());
+        return getBasedir().equals(getRootDirectory());
     }
 
     @Override

maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluatorV4.java

@@ -23,7 +23,6 @@
 import java.nio.file.Paths;
 import java.util.HashMap;
 import java.util.Map;
-import java.util.Optional;
 
 import org.apache.maven.api.MojoExecution;
 import org.apache.maven.api.Project;
@@ -76,12 +75,8 @@ public PluginParameterExpressionEvaluatorV4(Session session, Project project, Mo
         Path basedir = null;
 
         if (project != null) {
-            Optional<Path> projectFile = project.getBasedir();
-
-            // this should always be the case for non-super POM instances...
-            if (projectFile.isPresent()) {
-                basedir = projectFile.get().toAbsolutePath();
-            }
+            Path projectFile = project.getBasedir();
+            basedir = projectFile.toAbsolutePath();
         }
 
         if (basedir == null) {

maven-core/src/test/java/org/apache/maven/plugin/PluginParameterExpressionEvaluatorV4Test.java

@@ -186,10 +186,8 @@ public void testValueExtractionWithAPomValueContainingAPath() throws Exception {
     public void testEscapedVariablePassthrough() throws Exception {
         String var = "${var}";
 
-        Model model = new Model();
-        model.setVersion("1");
-
-        MavenProject project = new MavenProject(model);
+        MavenProject project = createDefaultProject();
+        project.setVersion("1");
 
         ExpressionEvaluator ee = createExpressionEvaluator(project, new Properties());
 
@@ -203,10 +201,8 @@ public void testEscapedVariablePassthroughInLargerExpression() throws Exception
         String var = "${var}";
         String key = var + " with version: ${project.version}";
 
-        Model model = new Model();
-        model.setVersion("1");
-
-        MavenProject project = new MavenProject(model);
+        MavenProject project = createDefaultProject();
+        project.setVersion("1");
 
         ExpressionEvaluator ee = createExpressionEvaluator(project, new Properties());
 
@@ -219,11 +215,9 @@ public void testEscapedVariablePassthroughInLargerExpression() throws Exception
     public void testMultipleSubExpressionsInLargerExpression() throws Exception {
         String key = "${project.artifactId} with version: ${project.version}";
 
-        Model model = new Model();
-        model.setArtifactId("test");
-        model.setVersion("1");
-
-        MavenProject project = new MavenProject(model);
+        MavenProject project = createDefaultProject();
+        project.setArtifactId("test");
+        project.setVersion("1");
 
         ExpressionEvaluator ee = createExpressionEvaluator(project, new Properties());
 
@@ -236,7 +230,7 @@ public void testMultipleSubExpressionsInLargerExpression() throws Exception {
     public void testMissingPOMPropertyRefInLargerExpression() throws Exception {
         String expr = "/path/to/someproject-${baseVersion}";
 
-        MavenProject project = new MavenProject(new Model());
+        MavenProject project = createDefaultProject();
 
         ExpressionEvaluator ee = createExpressionEvaluator(project, new Properties());
 
@@ -250,13 +244,8 @@ public void testPOMPropertyExtractionWithMissingProject_WithDotNotation() throws
         String key = "m2.name";
         String checkValue = "value";
 
-        Properties properties = new Properties();
-        properties.setProperty(key, checkValue);
-
-        Model model = new Model();
-        model.setProperties(properties);
-
-        MavenProject project = new MavenProject(model);
+        MavenProject project = createDefaultProject();
+        project.getModel().getProperties().setProperty(key, checkValue);
 
         ExpressionEvaluator ee = createExpressionEvaluator(project, new Properties());
 
@@ -320,14 +309,12 @@ private static MavenSession createSession(PlexusContainer container, ArtifactRep
 
     @Test
     public void testTwoExpressions() throws Exception {
-        Build build = new Build();
+        MavenProject project = createDefaultProject();
+        Build build = project.getBuild();
         build.setDirectory("expected-directory");
         build.setFinalName("expected-finalName");
 
-        Model model = new Model();
-        model.setBuild(build);
-
-        ExpressionEvaluator expressionEvaluator = createExpressionEvaluator(new MavenProject(model), new Properties());
+        ExpressionEvaluator expressionEvaluator = createExpressionEvaluator(project, new Properties());
 
         Object value = expressionEvaluator.evaluate("${project.build.directory}" + FS + "${project.build.finalName}");
 
@@ -375,7 +362,9 @@ void testRootDirectory() throws Exception {
     }
 
     private MavenProject createDefaultProject() {
-        return new MavenProject(new Model());
+        MavenProject project = new MavenProject(new Model());
+        project.setFile(new File("pom.xml").getAbsoluteFile());
+        return project;
     }
 
     private ExpressionEvaluator createExpressionEvaluator(MavenProject project, Properties executionProperties)