[MNG-8210] Replace Maven "module" term by "subproject"

api/maven-api-core/src/main/java/org/apache/maven/api/plugin/annotations/Mojo.java

@@ -76,8 +76,8 @@
     boolean projectRequired() default true;
 
     /**
-     * if the Mojo uses the Maven project and its child modules.
-     * @return uses the Maven project and its child modules
+     * if the Mojo uses the Maven project and its subprojects.
+     * @return uses the Maven project and its subprojectss
      */
     boolean aggregator() default false;
 

api/maven-api-core/src/main/java/org/apache/maven/api/services/ModelBuilder.java

@@ -25,7 +25,11 @@
 
 public interface ModelBuilder extends Service {
 
-    List<String> VALID_MODEL_VERSIONS = List.of("4.0.0", "4.1.0");
+    String MODEL_VERSION_4_0_0 = "4.0.0";
+
+    String MODEL_VERSION_4_1_0 = "4.0.0";
+
+    List<String> VALID_MODEL_VERSIONS = List.of(MODEL_VERSION_4_0_0, MODEL_VERSION_4_1_0);
 
     ModelBuilderResult build(ModelBuilderRequest request) throws ModelBuilderException;
 

api/maven-api-core/src/main/java/org/apache/maven/api/services/ModelProblem.java

@@ -35,7 +35,8 @@ enum Version {
         V20,
         V30,
         V31,
-        V40
+        V40,
+        V41
     }
 
     /**

api/maven-api-core/src/main/java/org/apache/maven/api/services/ModelSource.java

@@ -27,7 +27,7 @@
 
 /**
  * A Source specific to load POMs.  The {@link #resolve(ModelLocator, String)} method
- * will be used to find POMs for children modules.
+ * will be used to find POMs for subprojects.
  *
  * @since 4.0.0
  */

api/maven-api-model/src/main/mdo/maven.mdo

@@ -527,11 +527,22 @@
       <fields>
         <field xdoc.separator="blank">
           <name>modules</name>
-          <version>4.0.0+</version>
-          <description>The modules (sometimes called subprojects) to build as a part of this
-            project. Each module listed is a relative path to the directory containing the module.
-            To be consistent with the way default urls are calculated from parent, it is recommended
-            to have module names match artifact ids.</description>
+          <version>4.0.0/4.1.0</version>
+          <description>
+            @deprecated Use {@link #subprojects} instead.
+          </description>
+          <association>
+            <type>String</type>
+            <multiplicity>*</multiplicity>
+          </association>
+        </field>
+        <field xdoc.separator="blank">
+          <name>subprojects</name>
+          <version>4.1.0</version>
+          <description>The subprojects (formerly called modules) to build as a part of this
+            project. Each subproject listed is a relative path to the directory containing the subproject.
+            To be consistent with the way default URLs are calculated from parent, it is recommended
+            to have subproject names match artifact ids.</description>
           <association>
             <type>String</type>
             <multiplicity>*</multiplicity>
@@ -755,8 +766,8 @@
           <name>defaultGoal</name>
           <version>3.0.0+</version>
           <description>The default goal (or phase in Maven 2) to execute when none is specified for
-            the project. Note that in case of a multi-module build, only the default goal of the top-level
-            project is relevant, i.e. the default goals of child modules are ignored. Since Maven 3,
+            the project. Note that in case of a build with subprojects, only the default goal of the top-level
+            project is relevant, i.e. the default goals of subprojects are ignored. Since Maven 3,
             multiple goals/phases can be separated by whitespace.</description>
           <type>String</type>
         </field>

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

@@ -21,6 +21,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.lang.reflect.Field;
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -40,6 +41,7 @@
 import java.util.stream.Stream;
 
 import org.apache.maven.api.Session;
+import org.apache.maven.api.Type;
 import org.apache.maven.api.VersionRange;
 import org.apache.maven.api.annotations.Nullable;
 import org.apache.maven.api.di.Inject;
@@ -305,7 +307,7 @@ private Model readEffectiveModel(
             // Maven 3.x is always using 4.0.0 version to load the supermodel, so
             // do the same when loading a dependency.  The model validator will also
             // check that field later.
-            superModelVersion = "4.0.0";
+            superModelVersion = MODEL_VERSION_4_0_0;
         }
         ModelData superData = new ModelData(null, getSuperModel(superModelVersion));
 
@@ -737,6 +739,32 @@ private Model doReadFileModel(
 
         if (modelSource.getPath() != null) {
             model = model.withPomFile(modelSource.getPath());
+
+            // subprojects discovery
+            if (model.getSubprojects().isEmpty()
+                    && model.getModules().isEmpty()
+                    // only discover subprojects if POM > 4.0.0
+                    && !MODEL_VERSION_4_0_0.equals(model.getModelVersion())
+                    // and if packaging is POM (we check type, but the session is not yet available,
+                    // we would require the project realm if we want to support extensions
+                    && Type.POM.equals(model.getPackaging())) {
+                List<String> subprojects = new ArrayList<>();
+                try (Stream<Path> files = Files.list(model.getProjectDirectory())) {
+                    for (Path f : files.toList()) {
+                        if (Files.isDirectory(f)) {
+                            Path subproject = modelProcessor.locateExistingPom(f);
+                            if (subproject != null) {
+                                subprojects.add(f.getFileName().toString());
+                            }
+                        }
+                    }
+                    if (!subprojects.isEmpty()) {
+                        model = model.withSubprojects(subprojects);
+                    }
+                } catch (IOException e) {
+                    problems.add(Severity.FATAL, ModelProblem.Version.V41, "Error discovering subprojects", e);
+                }
+            }
         }
 
         problems.setSource(model);

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

@@ -644,6 +644,10 @@ public void validateEffectiveModel(Model m, ModelBuilderRequest request, ModelPr
 
         validateStringNotEmpty("packaging", problems, Severity.ERROR, Version.BASE, m.getPackaging(), m);
 
+        // TODO: if the model is a 4.1.0:
+        //   * modules should be empty, else issue a warning
+        //   * validate subprojects
+
         if (!m.getModules().isEmpty()) {
             if (!"pom".equals(m.getPackaging())) {
                 addViolation(

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

@@ -294,6 +294,7 @@ private static boolean isEmpty(Profile profile) {
                         || profile.getDependencyManagement().getDependencies().isEmpty())
                 && profile.getDistributionManagement() == null
                 && profile.getModules().isEmpty()
+                && profile.getSubprojects().isEmpty()
                 && profile.getProperties().isEmpty()
                 && profile.getRepositories().isEmpty()
                 && profile.getPluginRepositories().isEmpty()

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

@@ -121,6 +121,7 @@
 public class DefaultProjectBuilder implements ProjectBuilder {
     public static final String BUILDER_PARALLELISM = "maven.projectBuilder.parallelism";
     public static final int DEFAULT_BUILDER_PARALLELISM = Runtime.getRuntime().availableProcessors() / 2 + 1;
+    private static final String POM_4_0_0 = "4.0.0";
 
     private final Logger logger = LoggerFactory.getLogger(getClass());
     private final ModelBuilder modelBuilder;
@@ -275,7 +276,7 @@ static class InterimResult {
 
         boolean root;
 
-        List<InterimResult> modules = Collections.emptyList();
+        List<InterimResult> subprojects = Collections.emptyList();
 
         ProjectBuildingResult projectBuildingResult;
 
@@ -629,20 +630,24 @@ private InterimResult build(
 
             if (recursive) {
                 File basedir = pomFile.getParentFile();
-                List<File> moduleFiles = new ArrayList<>();
-                for (String module : model.getModules()) {
-                    if (module == null || module.isEmpty()) {
+                List<String> subprojects = model.getSubprojects();
+                if (subprojects.isEmpty()) {
+                    subprojects = model.getModules();
+                }
+                List<File> subprojectFiles = new ArrayList<>();
+                for (String subproject : subprojects) {
+                    if (subproject == null || subproject.isEmpty()) {
                         continue;
                     }
 
-                    module = module.replace('\\', File.separatorChar).replace('/', File.separatorChar);
+                    subproject = subproject.replace('\\', File.separatorChar).replace('/', File.separatorChar);
 
-                    Path modulePath = modelProcessor.locateExistingPom(new File(basedir, module).toPath());
-                    File moduleFile = modulePath != null ? modulePath.toFile() : null;
+                    Path subprojectPath = modelProcessor.locateExistingPom(new File(basedir, subproject).toPath());
+                    File subprojectFile = subprojectPath != null ? subprojectPath.toFile() : null;
 
-                    if (moduleFile == null) {
+                    if (subprojectFile == null) {
                         ModelProblem problem = new org.apache.maven.internal.impl.model.DefaultModelProblem(
-                                "Child module " + moduleFile + " of " + pomFile + " does not exist",
+                                "Child subproject " + subprojectFile + " of " + pomFile + " does not exist",
                                 ModelProblem.Severity.ERROR,
                                 ModelProblem.Version.BASE,
                                 model,
@@ -656,23 +661,24 @@ private InterimResult build(
                     if (Os.IS_WINDOWS) {
                         // we don't canonicalize on unix to avoid interfering with symlinks
                         try {
-                            moduleFile = moduleFile.getCanonicalFile();
+                            subprojectFile = subprojectFile.getCanonicalFile();
                         } catch (IOException e) {
-                            moduleFile = moduleFile.getAbsoluteFile();
+                            subprojectFile = subprojectFile.getAbsoluteFile();
                         }
                     } else {
-                        moduleFile = new File(moduleFile.toURI().normalize());
+                        subprojectFile = new File(subprojectFile.toURI().normalize());
                     }
 
-                    if (aggregatorFiles.contains(moduleFile)) {
+                    if (aggregatorFiles.contains(subprojectFile)) {
                         StringBuilder buffer = new StringBuilder(256);
                         for (File aggregatorFile : aggregatorFiles) {
                             buffer.append(aggregatorFile).append(" -> ");
                         }
-                        buffer.append(moduleFile);
+                        buffer.append(subprojectFile);
 
                         ModelProblem problem = new org.apache.maven.internal.impl.model.DefaultModelProblem(
-                                "Child module " + moduleFile + " of " + pomFile + " forms aggregation cycle " + buffer,
+                                "Child subproject " + subprojectFile + " of " + pomFile + " forms aggregation cycle "
+                                        + buffer,
                                 ModelProblem.Severity.ERROR,
                                 ModelProblem.Version.BASE,
                                 model,
@@ -684,11 +690,11 @@ private InterimResult build(
                         continue;
                     }
 
-                    moduleFiles.add(moduleFile);
+                    subprojectFiles.add(subprojectFile);
                 }
 
-                if (!moduleFiles.isEmpty()) {
-                    interimResult.modules = build(projectIndex, moduleFiles, aggregatorFiles, false, recursive);
+                if (!subprojectFiles.isEmpty()) {
+                    interimResult.subprojects = build(projectIndex, subprojectFiles, aggregatorFiles, false, recursive);
                 }
             }
 
@@ -780,7 +786,7 @@ private List<ProjectBuildingResult> doBuild(Map<File, MavenProject> projectIndex
                             iarte));
                 }
 
-                List<ProjectBuildingResult> results = build(projectIndex, interimResult.modules);
+                List<ProjectBuildingResult> results = build(projectIndex, interimResult.subprojects);
 
                 project.setExecutionRoot(interimResult.root);
                 project.setCollectedProjects(

maven-core/src/main/java/org/apache/maven/project/MavenProject.java

@@ -708,6 +708,9 @@ public List<Plugin> getBuildPlugins() {
     }
 
     public List<String> getModules() {
+        if (!getModel().getDelegate().getSubprojects().isEmpty()) {
+            return getModel().getDelegate().getSubprojects();
+        }
         return getModel().getModules();
     }
 

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

@@ -405,4 +405,18 @@ public void testBuildParentVersionRangeExternallyWithChildRevisionExpression() t
 
         assertEquals("1.0-SNAPSHOT", mp.getVersion());
     }
+
+    @Test
+    public void testSubprojectDiscovery() throws Exception {
+        File pom = getTestFile("src/test/resources/projects/subprojects-discover/pom.xml");
+        ProjectBuildingRequest configuration = newBuildingRequest();
+
+        List<ProjectBuildingResult> results = projectBuilder.build(List.of(pom), true, configuration);
+        assertEquals(2, results.size());
+        MavenProject p1 = results.get(0).getProject();
+        MavenProject p2 = results.get(1).getProject();
+        MavenProject parent = p1.getArtifactId().equals("parent") ? p1 : p2;
+        MavenProject child = p1.getArtifactId().equals("parent") ? p2 : p1;
+        assertEquals(List.of("child"), parent.getModel().getDelegate().getSubprojects());
+    }
 }

maven-core/src/test/resources/projects/subprojects-discover/child/pom.xml

@@ -0,0 +1,8 @@
+<project xmlns="http://maven.apache.org/POM/4.1.0">
+  <parent>
+    <groupId>subprojects-discover</groupId>
+    <artifactId>parent</artifactId>
+  </parent>
+  <artifactId>child</artifactId>
+  <packaging>jar</packaging>
+</project>

maven-core/src/test/resources/projects/subprojects-discover/pom.xml

@@ -0,0 +1,6 @@
+<project xmlns="http://maven.apache.org/POM/4.1.0">
+  <groupId>subprojects-discover</groupId>
+  <artifactId>parent</artifactId>
+  <version>1</version>
+  <packaging>pom</packaging>
+</project>