From 1dd329b23e51f69b4c3fa04d03dd57e0099dd72f Mon Sep 17 00:00:00 2001
From: Guillaume Nodet <gnodet@gmail.com>
Date: Thu, 16 Oct 2025 10:58:34 +0200
Subject: [PATCH 1/2] Maven model 4.1.0 should not allow non-pom packaging for
 aggregators

The check is working when using `modules`, but has been forgotten when introducing `subprojects`.
Fixes #11160
---
 .../impl/model/DefaultModelValidator.java     | 26 ++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/impl/maven-impl/src/main/java/org/apache/maven/impl/model/DefaultModelValidator.java b/impl/maven-impl/src/main/java/org/apache/maven/impl/model/DefaultModelValidator.java
index b97064f3117f..27b29148e90e 100644
--- a/impl/maven-impl/src/main/java/org/apache/maven/impl/model/DefaultModelValidator.java
+++ b/impl/maven-impl/src/main/java/org/apache/maven/impl/model/DefaultModelValidator.java
@@ -910,7 +910,7 @@ public void validateEffectiveModel(
 
         validateStringNotEmpty("packaging", problems, Severity.ERROR, Version.BASE, model.getPackaging(), model);
 
-        if (!model.getModules().isEmpty()) {
+        if (!model.getModules().isEmpty() || !model.getSubprojects().isEmpty()) {
             if (!"pom".equals(model.getPackaging())) {
                 addViolation(
                         problems,
@@ -946,6 +946,30 @@ public void validateEffectiveModel(
                             model.getLocation("modules"));
                 }
             }
+
+            for (int index = 0, size = model.getSubprojects().size(); index < size; index++) {
+                String subproject = model.getSubprojects().get(index);
+
+                boolean isBlankSubproject = true;
+                if (subproject != null) {
+                    for (int charIndex = 0; charIndex < subproject.length(); charIndex++) {
+                        if (!Character.isWhitespace(subproject.charAt(charIndex))) {
+                            isBlankSubproject = false;
+                        }
+                    }
+                }
+
+                if (isBlankSubproject) {
+                    addViolation(
+                            problems,
+                            Severity.ERROR,
+                            Version.BASE,
+                            "subprojects.subproject[" + index + "]",
+                            null,
+                            "has been specified without a path to the project directory.",
+                            model.getLocation("subprojects"));
+                }
+            }
         }
 
         validateStringNotEmpty("version", problems, Severity.ERROR, Version.BASE, model.getVersion(), model);

From a83cd29982b743d99209092b3fd26cbfb59c7f6f Mon Sep 17 00:00:00 2001
From: Guillaume Nodet <gnodet@gmail.com>
Date: Thu, 16 Oct 2025 14:41:58 +0200
Subject: [PATCH 2/2] Add unit tests

---
 .../impl/model/DefaultModelValidatorTest.java | 18 +++++++++++
 .../poms/validation/empty-subproject.xml      | 30 +++++++++++++++++++
 ...d-aggregator-packaging-subprojects-pom.xml | 30 +++++++++++++++++++
 3 files changed, 78 insertions(+)
 create mode 100644 impl/maven-impl/src/test/resources/poms/validation/empty-subproject.xml
 create mode 100644 impl/maven-impl/src/test/resources/poms/validation/invalid-aggregator-packaging-subprojects-pom.xml

diff --git a/impl/maven-impl/src/test/java/org/apache/maven/impl/model/DefaultModelValidatorTest.java b/impl/maven-impl/src/test/java/org/apache/maven/impl/model/DefaultModelValidatorTest.java
index 6e8397d708da..6ed648334089 100644
--- a/impl/maven-impl/src/test/java/org/apache/maven/impl/model/DefaultModelValidatorTest.java
+++ b/impl/maven-impl/src/test/java/org/apache/maven/impl/model/DefaultModelValidatorTest.java
@@ -543,6 +543,24 @@ void testEmptyModule() throws Exception {
         assertTrue(result.getErrors().get(0).contains("'modules.module[0]' has been specified without a path"));
     }
 
+    @Test
+    void testInvalidAggregatorPackagingSubprojects() throws Exception {
+        SimpleProblemCollector result = validate("invalid-aggregator-packaging-subprojects-pom.xml");
+
+        assertViolations(result, 0, 1, 0);
+
+        assertTrue(result.getErrors().get(0).contains("Aggregator projects require 'pom' as packaging."));
+    }
+
+    @Test
+    void testEmptySubproject() throws Exception {
+        SimpleProblemCollector result = validate("empty-subproject.xml");
+
+        assertViolations(result, 0, 1, 0);
+
+        assertTrue(result.getErrors().get(0).contains("'subprojects.subproject[0]' has been specified without a path"));
+    }
+
     @Test
     void testDuplicatePlugin() throws Exception {
         SimpleProblemCollector result = validateFile("duplicate-plugin.xml");
diff --git a/impl/maven-impl/src/test/resources/poms/validation/empty-subproject.xml b/impl/maven-impl/src/test/resources/poms/validation/empty-subproject.xml
new file mode 100644
index 000000000000..03e039f3e833
--- /dev/null
+++ b/impl/maven-impl/src/test/resources/poms/validation/empty-subproject.xml
@@ -0,0 +1,30 @@
+<!--
+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>
+  <modelVersion>4.1.0</modelVersion>
+  <artifactId>aid</artifactId>
+  <groupId>gid</groupId>
+  <version>0.1</version>
+  <packaging>pom</packaging>
+
+  <subprojects>
+    <subproject> </subproject>
+  </subprojects>
+</project>
diff --git a/impl/maven-impl/src/test/resources/poms/validation/invalid-aggregator-packaging-subprojects-pom.xml b/impl/maven-impl/src/test/resources/poms/validation/invalid-aggregator-packaging-subprojects-pom.xml
new file mode 100644
index 000000000000..c4121ded842f
--- /dev/null
+++ b/impl/maven-impl/src/test/resources/poms/validation/invalid-aggregator-packaging-subprojects-pom.xml
@@ -0,0 +1,30 @@
+<!--
+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>
+  <modelVersion>4.1.0</modelVersion>
+  <artifactId>foo</artifactId>
+  <groupId>foo</groupId>
+  <version>99.44</version>
+  <packaging>jar</packaging>
+
+  <subprojects>
+    <subproject>test-subproject</subproject>
+  </subprojects>
+</project>