Resolve classified POM artifacts from the reactor in Maven 3.x

maven-core/src/main/java/org/apache/maven/ReactorReader.java

@@ -129,7 +129,8 @@ public Model findModel(Artifact artifact) {
     //
 
     private File find(MavenProject project, Artifact artifact) {
-        if ("pom".equals(artifact.getExtension())) {
+        if ("pom".equals(artifact.getExtension())
+                && (artifact.getClassifier() == null || artifact.getClassifier().isEmpty())) {
             return project.getFile();
         }
 

maven-core/src/test/java/org/apache/maven/ReactorReaderTest.java

@@ -0,0 +1,79 @@
+/*
+ * 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;
+
+import java.io.File;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collections;
+
+import org.apache.maven.artifact.Artifact;
+import org.apache.maven.artifact.DefaultArtifact;
+import org.apache.maven.artifact.handler.DefaultArtifactHandler;
+import org.apache.maven.execution.MavenSession;
+import org.apache.maven.project.MavenProject;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+class ReactorReaderTest {
+
+    @TempDir
+    Path tempDir;
+
+    @Test
+    void classifiedPomShouldResolveToAttachedArtifact() throws Exception {
+        File projectPom = Files.createFile(tempDir.resolve("pom.xml")).toFile();
+        File attachedPom = Files.createFile(tempDir.resolve("custom.pom")).toFile();
+
+        MavenProject project = new MavenProject();
+        project.setGroupId("org.apache.maven.its.mdep590");
+        project.setArtifactId("producer");
+        project.setVersion("1.0-SNAPSHOT");
+        project.setFile(projectPom);
+        project.setArtifact(newArtifact(null, projectPom));
+        project.addAttachedArtifact(newArtifact("custom", attachedPom));
+
+        MavenSession session = mock(MavenSession.class);
+        when(session.getProjects()).thenReturn(Collections.singletonList(project));
+
+        ReactorReader reader = new ReactorReader(session);
+
+        assertEquals(
+                attachedPom,
+                reader.findArtifact(new org.eclipse.aether.artifact.DefaultArtifact(
+                        "org.apache.maven.its.mdep590:producer:pom:custom:1.0-SNAPSHOT")));
+    }
+
+    private static Artifact newArtifact(String classifier, File file) {
+        Artifact artifact = new DefaultArtifact(
+                "org.apache.maven.its.mdep590",
+                "producer",
+                "1.0-SNAPSHOT",
+                Artifact.SCOPE_COMPILE,
+                "pom",
+                classifier,
+                new DefaultArtifactHandler("pom"));
+        artifact.setFile(file);
+        return artifact;
+    }
+}