[MNG-7836] Support alternative syntaxes for POMs

# Conflicts:
#	maven-model-builder/src/main/java/org/apache/maven/model/building/DefaultModelProcessor.java

Author: gnodet

.github/workflows/maven.yml

@@ -106,19 +106,21 @@ jobs:
           ref: ${{ env.REPO_BRANCH }}
           persist-credentials: false
 
-      - name: Download built Maven
-        uses: actions/download-artifact@v3
-        with:
-          name: built-maven
-          path: built-maven/
-
       - name: Set up JDK
         uses: actions/setup-java@v3
         with:
           java-version: ${{ matrix.java }}
           distribution: 'temurin'
 #          cache: 'maven' - don't use cache for integration tests
 
+      - uses: actions/checkout@v3
+        with:
+          path: maven/
+          persist-credentials: false
+
+      - name: Build Maven
+        run: mvn install -e -B -V -DdistributionFileName=apache-maven -DskipTests -f maven/pom.xml
+
       - name: Running integration tests
         shell: bash
-        run: mvn install -e -B -V -Prun-its,embedded -DmavenDistro="$GITHUB_WORKSPACE/built-maven/apache-maven-bin.zip" -f maven-integration-testing/pom.xml
+        run: mvn install -e -B -V -Prun-its,embedded -DmavenDistro="$GITHUB_WORKSPACE/maven/apache-maven/target/apache-maven-bin.zip" -f maven-integration-testing/pom.xml

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

@@ -0,0 +1,54 @@
+/*
+ * 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.api.services;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Objects;
+
+import org.apache.maven.api.annotations.Nonnull;
+
+public class PathSource implements Source {
+
+    private final Path path;
+
+    public PathSource(@Nonnull Path path) {
+        this.path = Objects.requireNonNull(path);
+    }
+
+    @Nonnull
+    @Override
+    public Path getPath() {
+        return path;
+    }
+
+    @Nonnull
+    @Override
+    public InputStream openStream() throws IOException {
+        return Files.newInputStream(path);
+    }
+
+    @Nonnull
+    @Override
+    public String getLocation() {
+        return path.toString();
+    }
+}

api/maven-api-model/pom.xml

@@ -76,6 +76,26 @@ under the License.
           </excludes>
         </configuration>
       </plugin>
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>build-helper-maven-plugin</artifactId>
+        <version>3.4.0</version>
+        <executions>
+          <execution>
+            <goals>
+              <goal>attach-artifact</goal>
+            </goals>
+            <configuration>
+              <artifacts>
+                <artifact>
+                  <file>${basedir}/src/main/mdo/maven.mdo</file>
+                  <type>mdo</type>
+                </artifact>
+              </artifacts>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
     </plugins>
   </build>
 

api/maven-api-spi/src/main/java/org/apache/maven/api/spi/ModelParser.java

@@ -0,0 +1,71 @@
+/*
+ * 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.api.spi;
+
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.Optional;
+
+import org.apache.maven.api.annotations.Experimental;
+import org.apache.maven.api.annotations.Nonnull;
+import org.apache.maven.api.annotations.Nullable;
+import org.apache.maven.api.model.Model;
+import org.apache.maven.api.services.Source;
+
+/**
+ * The {@code ModelParser} interface is used to locate and read {@link Model}s from the file system.
+ * This allows plugging in additional syntaxes for the main model read by Maven when building a project.
+ */
+@Experimental
+public interface ModelParser {
+
+    /**
+     * Locates the pom in the given directory.
+     *
+     * @param dir the directory to locate the pom for, never {@code null}
+     * @return a {@code Source} pointing to the located pom or an empty {@code Optional} if none was found by this parser
+     */
+    @Nonnull
+    Optional<Source> locate(@Nonnull Path dir);
+
+    /**
+     * Parse the model obtained previously by a previous call to {@link #locate(Path)}.
+     *
+     * @param source the source to parse, never {@code null}
+     * @param options possible parsing options, may be {@code null}
+     * @return the parsed {@link Model}, never {@code null}
+     * @throws ModelParserException if the model cannot be parsed
+     */
+    @Nonnull
+    Model parse(@Nonnull Source source, @Nullable Map<String, ?> options) throws ModelParserException;
+
+    /**
+     * Locate and parse the model in the specified directory.
+     * This is equivalent to {@code locate(dir).map(s -> parse(s, options))}.
+     *
+     * @param dir the directory to locate the pom for, never {@code null}
+     * @param options possible parsing options, may be {@code null}
+     * @return an optional parsed {@link Model} or {@code null} if none could be found
+     * @throws ModelParserException if the located model cannot be parsed
+     */
+    default Optional<Model> locateAndParse(@Nonnull Path dir, @Nullable Map<String, ?> options)
+            throws ModelParserException {
+        return locate(dir).map(s -> parse(s, options));
+    }
+}

api/maven-api-spi/src/main/java/org/apache/maven/api/spi/ModelParserException.java

@@ -0,0 +1,66 @@
+/*
+ * 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.api.spi;
+
+import org.apache.maven.api.annotations.Experimental;
+import org.apache.maven.api.services.MavenException;
+
+@Experimental
+public class ModelParserException extends MavenException {
+
+    /**
+     * The one-based index of the line containing the error.
+     */
+    private final int lineNumber;
+
+    /**
+     * The one-based index of the column containing the error.
+     */
+    private final int columnNumber;
+
+    public ModelParserException() {
+        this(null, null);
+    }
+
+    public ModelParserException(String message) {
+        this(message, null);
+    }
+
+    public ModelParserException(String message, Throwable cause) {
+        this(message, -1, -1, cause);
+    }
+
+    public ModelParserException(String message, int lineNumber, int columnNumber, Throwable cause) {
+        super(message, cause);
+        this.lineNumber = lineNumber;
+        this.columnNumber = columnNumber;
+    }
+
+    public ModelParserException(Throwable cause) {
+        this(null, cause);
+    }
+
+    public int getLineNumber() {
+        return lineNumber;
+    }
+
+    public int getColumnNumber() {
+        return columnNumber;
+    }
+}

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

@@ -19,28 +19,34 @@
 package org.apache.maven.internal.transformation;
 
 import javax.annotation.PreDestroy;
+import javax.inject.Inject;
 import javax.inject.Named;
 import javax.inject.Singleton;
 import javax.xml.stream.XMLStreamException;
 import javax.xml.stream.XMLStreamReader;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.io.OutputStream;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
-import java.nio.file.StandardCopyOption;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.CopyOnWriteArraySet;
 import java.util.function.BiConsumer;
 
 import org.apache.maven.api.feature.Features;
+import org.apache.maven.api.model.Model;
+import org.apache.maven.api.services.Source;
+import org.apache.maven.api.spi.ModelParser;
 import org.apache.maven.model.building.DefaultBuildPomXMLFilterFactory;
 import org.apache.maven.model.building.TransformerContext;
 import org.apache.maven.model.transform.RawToConsumerPomXMLFilterFactory;
 import org.apache.maven.model.transform.stax.XmlUtils;
+import org.apache.maven.model.v4.MavenStaxWriter;
 import org.apache.maven.project.MavenProject;
 import org.apache.maven.project.artifact.ProjectArtifact;
 import org.codehaus.stax2.XMLInputFactory2;
@@ -63,6 +69,13 @@ public final class ConsumerPomArtifactTransformer {
 
     private final Set<Path> toDelete = new CopyOnWriteArraySet<>();
 
+    private final Map<String, ModelParser> modelParsers;
+
+    @Inject
+    ConsumerPomArtifactTransformer(Map<String, ModelParser> modelParsers) {
+        this.modelParsers = modelParsers;
+    }
+
     public void injectTransformedArtifacts(MavenProject project, RepositorySystemSession session) throws IOException {
         if (project.getFile() == null) {
             // If there is no build POM there is no reason to inject artifacts for the consumer POM.
@@ -150,7 +163,7 @@ private Collection<Artifact> replacePom(Collection<Artifact> artifacts) {
     /**
      * Consumer POM is transformed from original POM.
      */
-    private static class ConsumerPomArtifact extends TransformedArtifact {
+    private class ConsumerPomArtifact extends TransformedArtifact {
 
         private ConsumerPomArtifact(MavenProject mavenProject, Path target, RepositorySystemSession session) {
             super(
@@ -161,31 +174,56 @@ private ConsumerPomArtifact(MavenProject mavenProject, Path target, RepositorySy
                     target,
                     transformer(session));
         }
+    }
 
-        private static BiConsumer<Path, Path> transformer(RepositorySystemSession session) {
-            TransformerContext context = (TransformerContext) session.getData().get(TransformerContext.KEY);
-            return (src, dest) -> {
-                try (InputStream inputStream = transform(src, context)) {
-                    Files.createDirectories(dest.getParent());
-                    Files.copy(inputStream, dest, StandardCopyOption.REPLACE_EXISTING);
-                } catch (XMLStreamException | IOException e) {
-                    throw new RuntimeException(e);
-                }
-            };
-        }
+    BiConsumer<Path, Path> transformer(RepositorySystemSession session) {
+        TransformerContext context = (TransformerContext) session.getData().get(TransformerContext.KEY);
+        return (src, dest) -> {
+            try {
+                Files.createDirectories(dest.getParent());
+                transform(src, dest, context);
+            } catch (XMLStreamException | IOException e) {
+                throw new RuntimeException(e);
+            }
+        };
     }
 
     /**
      * The actual transformation: visible for testing.
      */
-    static InputStream transform(Path pomFile, TransformerContext context) throws IOException, XMLStreamException {
-        try (InputStream input = Files.newInputStream(pomFile)) {
-            XMLInputFactory2 factory = new com.ctc.wstx.stax.WstxInputFactory();
-            factory.configureForRoundTripping();
-            XMLStreamReader reader = factory.createXMLStreamReader(input);
-            reader = new RawToConsumerPomXMLFilterFactory(new DefaultBuildPomXMLFilterFactory(context, true))
-                    .get(reader, pomFile);
-            return XmlUtils.writeDocument(reader);
+    void transform(Path pomFile, Path destPomFile, TransformerContext context) throws IOException, XMLStreamException {
+        ModelParser parser = null;
+        Source source = null;
+        for (ModelParser p : modelParsers.values()) {
+            source = p.locate(pomFile).orElse(null);
+            if (source != null) {
+                parser = p;
+                break;
+            }
+        }
+
+        if (source != null) {
+            try (OutputStream output = Files.newOutputStream(destPomFile)) {
+                Model model = parser.parse(source, null);
+                // transform
+                model = model.withRoot(false).withModules(null);
+                if (model.getParent() != null) {
+                    model = model.withParent(model.getParent().withRelativePath(null));
+                }
+                MavenStaxWriter w = new MavenStaxWriter();
+                w.write(output, model);
+            }
+        } else {
+            try (OutputStream output = Files.newOutputStream(destPomFile)) {
+                try (InputStream input = Files.newInputStream(pomFile)) {
+                    XMLInputFactory2 factory = new com.ctc.wstx.stax.WstxInputFactory();
+                    factory.configureForRoundTripping();
+                    XMLStreamReader reader = factory.createXMLStreamReader(input);
+                    reader = new RawToConsumerPomXMLFilterFactory(new DefaultBuildPomXMLFilterFactory(context, true))
+                            .get(reader, pomFile);
+                    XmlUtils.writeDocument(reader, output);
+                }
+            }
         }
     }
 }