Fix #12646: project-local-repo clean race condition when root pom has parent

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

@@ -352,6 +352,12 @@ private File findInProjectLocalRepository(Artifact artifact) {
      * The mojo started event is also captured to determine the lifecycle
      * phases the project has been through.
      *
+     * <p>When a project enters its clean phase, its artifacts are cleaned from the
+     * project-local-repo (per-GAV scope). Since the project-local-repo is located
+     * under {@code .mvn/} (not under {@code target/}), it is not affected by
+     * maven-clean-plugin's deletion of {@code target/}, eliminating the race
+     * condition between clean and install operations in parallel builds.</p>
+     *
      * @param event the execution event
      */
     private void processEvent(ExecutionEvent event) {
@@ -364,9 +370,7 @@ private void processEvent(ExecutionEvent event) {
                     if (!Objects.equals(phase, phases.peekLast())) {
                         phases.addLast(phase);
                         if ("clean".equals(phase)) {
-                            synchronized (project) {
-                                cleanProjectLocalRepository(project);
-                            }
+                            cleanProjectLocalRepository(project);
                         }
                     }
                 }
@@ -402,6 +406,12 @@ private void installIntoProjectLocalRepository(MavenProject project) {
         }
     }
 
+    /**
+     * Cleans the project-local-repo artifacts for the given project's GAV coordinates.
+     * Since the project-local-repo is under {@code .mvn/} and not {@code target/},
+     * it is not affected by maven-clean-plugin's deletion of {@code target/},
+     * so there is no race between clean and install operations in parallel builds.
+     */
     private void cleanProjectLocalRepository(MavenProject project) {
         try {
             Path artifactPath = getProjectLocalRepo()
@@ -505,18 +515,7 @@ private Path getArtifactPath(
     private Path getProjectLocalRepo() {
         if (projectLocalRepository == null) {
             Path root = session.getRequest().getRootDirectory();
-            List<MavenProject> projects = session.getProjects();
-            if (projects != null) {
-                projectLocalRepository = projects.stream()
-                        .filter(project -> Objects.equals(root.toFile(), project.getBasedir()))
-                        .findFirst()
-                        .map(project -> project.getBuild().getDirectory())
-                        .map(Paths::get)
-                        .orElseGet(() -> root.resolve("target"))
-                        .resolve(PROJECT_LOCAL_REPO);
-            } else {
-                return root.resolve("target").resolve(PROJECT_LOCAL_REPO);
-            }
+            projectLocalRepository = root.resolve(".mvn").resolve(PROJECT_LOCAL_REPO);
         }
         return projectLocalRepository;
     }

its/core-it-suite/src/test/java/org/apache/maven/it/MavenITgh12646ProjectLocalRepoCleanRaceTest.java

@@ -0,0 +1,59 @@
+/*
+ * 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.it;
+
+import java.nio.file.Path;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * This is a test set for <a href="https://github.com/apache/maven/issues/12646">GH-12646</a>.
+ *
+ * Verifies that parallel builds with {@code clean install} do not fail with a race condition
+ * when the root pom has a parent (super-pom) and other modules write to
+ * {@code target/project-local-repo} while the root project's clean phase is running.
+ *
+ * @since 4.0.0-rc-6
+ */
+class MavenITgh12646ProjectLocalRepoCleanRaceTest extends AbstractMavenIntegrationTestCase {
+
+    /**
+     * Verify that a parallel {@code clean install} succeeds when the root pom has a parent
+     * that is also part of the reactor. In this scenario:
+     * <ol>
+     *   <li>super-pom builds first (no dependencies)</li>
+     *   <li>root pom and module-a..d start in parallel (all depend on super-pom)</li>
+     *   <li>root pom's clean phase runs maven-clean-plugin which deletes target/</li>
+     *   <li>modules complete and install artifacts into target/project-local-repo</li>
+     * </ol>
+     * Without the fix, step 3 and 4 race, causing maven-clean-plugin to fail because
+     * target/project-local-repo is being written to while it tries to delete target/.
+     */
+    @Test
+    void testParallelCleanInstallWithParentPom() throws Exception {
+        Path testDir = extractResources("gh-12646-project-local-repo-clean-race");
+
+        Verifier verifier = newVerifier(testDir);
+        verifier.addCliArgument("-T");
+        verifier.addCliArgument("4");
+        verifier.addCliArguments("clean", "install");
+        verifier.execute();
+        verifier.verifyErrorFreeLog();
+    }
+}

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/pom.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+    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.
+-->
+<project xmlns="http://maven.apache.org/POM/4.1.0">
+  <parent>
+    <groupId>org.apache.maven.its.gh12646</groupId>
+    <artifactId>super-pom</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <relativePath>../super-pom</relativePath>
+  </parent>
+
+  <artifactId>module-a</artifactId>
+</project>

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-a/src/main/java/a/A.java

@@ -0,0 +1,7 @@
+package a;
+
+public class A {
+    public String greet() {
+        return "Hello from A";
+    }
+}

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/pom.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+    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.
+-->
+<project xmlns="http://maven.apache.org/POM/4.1.0">
+  <parent>
+    <groupId>org.apache.maven.its.gh12646</groupId>
+    <artifactId>super-pom</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <relativePath>../super-pom</relativePath>
+  </parent>
+
+  <artifactId>module-b</artifactId>
+</project>

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-b/src/main/java/b/B.java

@@ -0,0 +1,7 @@
+package b;
+
+public class B {
+    public String greet() {
+        return "Hello from B";
+    }
+}

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/pom.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+    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.
+-->
+<project xmlns="http://maven.apache.org/POM/4.1.0">
+  <parent>
+    <groupId>org.apache.maven.its.gh12646</groupId>
+    <artifactId>super-pom</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <relativePath>../super-pom</relativePath>
+  </parent>
+
+  <artifactId>module-c</artifactId>
+</project>

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-c/src/main/java/c/C.java

@@ -0,0 +1,7 @@
+package c;
+
+public class C {
+    public String greet() {
+        return "Hello from C";
+    }
+}

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/pom.xml

@@ -0,0 +1,29 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+    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.
+-->
+<project xmlns="http://maven.apache.org/POM/4.1.0">
+  <parent>
+    <groupId>org.apache.maven.its.gh12646</groupId>
+    <artifactId>super-pom</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <relativePath>../super-pom</relativePath>
+  </parent>
+
+  <artifactId>module-d</artifactId>
+</project>

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/module-d/src/main/java/d/D.java

@@ -0,0 +1,7 @@
+package d;
+
+public class D {
+    public String greet() {
+        return "Hello from D";
+    }
+}

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/pom.xml

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+    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.
+-->
+<project xmlns="http://maven.apache.org/POM/4.1.0" root="true">
+  <parent>
+    <groupId>org.apache.maven.its.gh12646</groupId>
+    <artifactId>super-pom</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <relativePath>super-pom</relativePath>
+  </parent>
+
+  <artifactId>root</artifactId>
+  <packaging>pom</packaging>
+
+  <modules>
+    <module>super-pom</module>
+    <module>module-a</module>
+    <module>module-b</module>
+    <module>module-c</module>
+    <module>module-d</module>
+  </modules>
+</project>

its/core-it-suite/src/test/resources/gh-12646-project-local-repo-clean-race/super-pom/pom.xml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+    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.
+-->
+<project xmlns="http://maven.apache.org/POM/4.1.0">
+  <groupId>org.apache.maven.its.gh12646</groupId>
+  <artifactId>super-pom</artifactId>
+  <version>1.0-SNAPSHOT</version>
+  <packaging>pom</packaging>
+</project>