Fix [unknown project] messages in error output (#11324)

Resolves issue #11292 where Maven shows '[unknown project]' in error
messages when using -e -X flags, particularly in CI environments.

The issue occurred because DefaultProjectBuilder was creating
DefaultProjectBuildingResult with null project information when
ModelBuilderResult.getEffectiveModel() returned null, resulting in
empty projectId and causing ProjectBuildingException.createMessage()
to display '[unknown project]' as a fallback.

This fix extracts project identification from available model data
(rawModel or fileModel) when effectiveModel is null, following the
same pattern used in ModelBuilderException.getModelId().

Changes:
- Added extractProjectId() helper method that falls back to rawModel
  or fileModel when effectiveModel is null
- Modified project building result creation to use extracted projectId
  and POM file information instead of null values
- Maintains backward compatibility: when all models are null, still
  returns empty string to preserve '[unknown project]' fallback for
  truly unknown projects

This provides better error messages showing meaningful project
identification like 'com.example:my-project:jar:1.0.0' even when
project building fails, while maintaining existing error handling
patterns.

Author: gnodet

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

@@ -581,7 +581,13 @@ private List<ProjectBuildingResult> build(File pomFile, boolean recursive) {
                     results.add(new DefaultProjectBuildingResult(
                             project, convert(r.getProblemCollector()), resolutionResult));
                 } else {
-                    results.add(new DefaultProjectBuildingResult(null, convert(r.getProblemCollector()), null));
+                    // Extract project identification even when effective model is null
+                    String projectId = extractProjectId(r);
+                    File sourcePomFile = r.getSource() != null && r.getSource().getPath() != null
+                            ? r.getSource().getPath().toFile()
+                            : null;
+                    results.add(new DefaultProjectBuildingResult(
+                            projectId, sourcePomFile, convert(r.getProblemCollector())));
                 }
             }
             return results;
@@ -1013,6 +1019,27 @@ private static ModelSource createStubModelSource(Artifact artifact) {
         return new StubModelSource(xml, artifact);
     }
 
+    /**
+     * Extracts project identification from ModelBuilderResult, falling back to rawModel or fileModel
+     * when effectiveModel is null, similar to ModelBuilderException.getModelId().
+     */
+    private static String extractProjectId(ModelBuilderResult result) {
+        Model model = null;
+        if (result.getEffectiveModel() != null) {
+            model = result.getEffectiveModel();
+        } else if (result.getRawModel() != null) {
+            model = result.getRawModel();
+        } else if (result.getFileModel() != null) {
+            model = result.getFileModel();
+        }
+
+        if (model != null) {
+            return model.getId();
+        }
+
+        return "";
+    }
+
     static String getGroupId(Model model) {
         String groupId = model.getGroupId();
         if (groupId == null && model.getParent() != null) {

impl/maven-core/src/test/java/org/apache/maven/project/DefaultProjectBuilderTest.java

@@ -0,0 +1,214 @@
+/*
+ * 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.project;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.lang.reflect.Method;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.List;
+
+import org.apache.maven.api.model.Model;
+import org.apache.maven.api.model.Profile;
+import org.apache.maven.api.services.ModelBuilderRequest;
+import org.apache.maven.api.services.ModelBuilderResult;
+import org.apache.maven.api.services.ModelProblem;
+import org.apache.maven.api.services.ModelSource;
+import org.apache.maven.api.services.ProblemCollector;
+import org.apache.maven.api.services.Source;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+/**
+ * Test for {@link DefaultProjectBuilder} extractProjectId method.
+ */
+@SuppressWarnings("deprecation")
+class DefaultProjectBuilderTest {
+
+    /**
+     * Test the extractProjectId method to ensure it properly falls back to rawModel or fileModel
+     * when effectiveModel is null, addressing issue #11292.
+     */
+    @Test
+    void testExtractProjectIdFallback() throws Exception {
+        // Use reflection to access the private extractProjectId method
+        Method extractProjectIdMethod =
+                DefaultProjectBuilder.class.getDeclaredMethod("extractProjectId", ModelBuilderResult.class);
+        extractProjectIdMethod.setAccessible(true);
+
+        // Create a mock ModelBuilderResult with null effectiveModel but available rawModel
+        ModelBuilderResult mockResult = new MockModelBuilderResult(
+                null, // effectiveModel is null
+                createMockModel("com.example", "test-project", "1.0.0"), // rawModel is available
+                null // fileModel is null
+                );
+
+        String projectId = (String) extractProjectIdMethod.invoke(null, mockResult);
+
+        assertNotNull(projectId, "Project ID should not be null");
+        assertEquals(
+                "com.example:test-project:jar:1.0.0",
+                projectId,
+                "Should extract project ID from rawModel when effectiveModel is null");
+    }
+
+    /**
+     * Test extractProjectId with fileModel fallback when both effectiveModel and rawModel are null.
+     */
+    @Test
+    void testExtractProjectIdFileModelFallback() throws Exception {
+        Method extractProjectIdMethod =
+                DefaultProjectBuilder.class.getDeclaredMethod("extractProjectId", ModelBuilderResult.class);
+        extractProjectIdMethod.setAccessible(true);
+
+        ModelBuilderResult mockResult = new MockModelBuilderResult(
+                null, // effectiveModel is null
+                null, // rawModel is null
+                createMockModel("com.example", "test-project", "1.0.0") // fileModel is available
+                );
+
+        String projectId = (String) extractProjectIdMethod.invoke(null, mockResult);
+
+        assertNotNull(projectId, "Project ID should not be null");
+        assertEquals(
+                "com.example:test-project:jar:1.0.0",
+                projectId,
+                "Should extract project ID from fileModel when effectiveModel and rawModel are null");
+    }
+
+    /**
+     * Test extractProjectId returns empty string when all models are null.
+     */
+    @Test
+    void testExtractProjectIdAllModelsNull() throws Exception {
+        Method extractProjectIdMethod =
+                DefaultProjectBuilder.class.getDeclaredMethod("extractProjectId", ModelBuilderResult.class);
+        extractProjectIdMethod.setAccessible(true);
+
+        ModelBuilderResult mockResult = new MockModelBuilderResult(null, null, null);
+
+        String projectId = (String) extractProjectIdMethod.invoke(null, mockResult);
+
+        assertNotNull(projectId, "Project ID should not be null");
+        assertEquals("", projectId, "Should return empty string when all models are null");
+    }
+
+    private Model createMockModel(String groupId, String artifactId, String version) {
+        return Model.newBuilder()
+                .groupId(groupId)
+                .artifactId(artifactId)
+                .version(version)
+                .packaging("jar")
+                .build();
+    }
+
+    /**
+     * Mock implementation of ModelBuilderResult for testing.
+     */
+    private static class MockModelBuilderResult implements ModelBuilderResult {
+        private final Model effectiveModel;
+        private final Model rawModel;
+        private final Model fileModel;
+
+        MockModelBuilderResult(Model effectiveModel, Model rawModel, Model fileModel) {
+            this.effectiveModel = effectiveModel;
+            this.rawModel = rawModel;
+            this.fileModel = fileModel;
+        }
+
+        @Override
+        public Model getEffectiveModel() {
+            return effectiveModel;
+        }
+
+        @Override
+        public Model getRawModel() {
+            return rawModel;
+        }
+
+        @Override
+        public Model getFileModel() {
+            return fileModel;
+        }
+
+        @Override
+        public ModelBuilderRequest getRequest() {
+            return null;
+        }
+
+        // Other required methods with minimal implementations
+        @Override
+        public ModelSource getSource() {
+            return new ModelSource() {
+                @Override
+                public Path getPath() {
+                    return Paths.get("test-pom.xml");
+                }
+
+                @Override
+                public String getLocation() {
+                    return "test-pom.xml";
+                }
+
+                @Override
+                public InputStream openStream() throws IOException {
+                    return null;
+                }
+
+                @Override
+                public Source resolve(String relative) {
+                    return null;
+                }
+
+                @Override
+                public ModelSource resolve(ModelSource.ModelLocator modelLocator, String relative) {
+                    return null;
+                }
+            };
+        }
+
+        @Override
+        public Model getParentModel() {
+            return null;
+        }
+
+        @Override
+        public List<Profile> getActivePomProfiles() {
+            return List.of();
+        }
+
+        @Override
+        public List<Profile> getActiveExternalProfiles() {
+            return List.of();
+        }
+
+        @Override
+        public ProblemCollector<ModelProblem> getProblemCollector() {
+            return null;
+        }
+
+        @Override
+        public List<? extends ModelBuilderResult> getChildren() {
+            return List.of();
+        }
+    }
+}