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The following commit(s) were added to refs/heads/master by this push:
new 8f63dcca21 Add validation for mixins in consumer POM without
flattening (fixes #11456) (#11463)
8f63dcca21 is described below
commit 8f63dcca21d0f91dc092312b701142e7fbe455c7
Author: Guillaume Nodet <[email protected]>
AuthorDate: Thu Nov 27 08:40:26 2025 +0100
Add validation for mixins in consumer POM without flattening (fixes #11456)
(#11463)
Maven now fails with a clear error message when a POM contains mixins
but consumer POM flattening is disabled. Mixins require model version 4.2.0
and cannot be part of the consumer POM, so they must be removed during
transformation through flattening.
Changes:
- Added validation in DefaultConsumerPomBuilder to check for mixins when
flattening is disabled and throw MavenException with helpful message
- Added integration test MavenITgh11456MixinsConsumerPomTest with three
scenarios
The error message guides users to either enable flattening by setting
maven.consumer.pom.flatten=true, using preserve.model.version=true, or
remove mixins from their POM.
Fixes https://github.com/apache/maven/issues/11456
---
.../impl/DefaultConsumerPomBuilder.java | 54 +++++++++
.../it/MavenITgh11456MixinsConsumerPomTest.java | 125 +++++++++++++++++++++
.../apache/maven/it/MavenITmng5102MixinsTest.java | 4 +-
.../flattened/.mvn/.gitkeep | 0
.../flattened/.mvn/maven-user.properties | 1 +
.../gh-11456-mixins-consumer-pom/flattened/pom.xml | 38 +++++++
.../1.0/test-mixin-flattened-1.0.pom | 13 +++
.../flattened/src/main/java/Test.java | 20 ++++
.../non-flattened/.mvn/.gitkeep | 0
.../non-flattened/pom.xml | 38 +++++++
.../its/gh11456/test-mixin/1.0/test-mixin-1.0.pom | 13 +++
.../non-flattened/src/main/java/Test.java | 20 ++++
.../preserve-model-version/.mvn/.gitkeep | 0
.../preserve-model-version/.mvn/maven.properties | 1 +
.../preserve-model-version/pom.xml | 38 +++++++
.../1.0/test-mixin-flattened-1.0.pom | 13 +++
.../preserve-model-version/src/main/java/Test.java | 20 ++++
17 files changed, 396 insertions(+), 2 deletions(-)
diff --git
a/impl/maven-core/src/main/java/org/apache/maven/internal/transformation/impl/DefaultConsumerPomBuilder.java
b/impl/maven-core/src/main/java/org/apache/maven/internal/transformation/impl/DefaultConsumerPomBuilder.java
index 6f6ff80abe..c46d3d5b6d 100644
---
a/impl/maven-core/src/main/java/org/apache/maven/internal/transformation/impl/DefaultConsumerPomBuilder.java
+++
b/impl/maven-core/src/main/java/org/apache/maven/internal/transformation/impl/DefaultConsumerPomBuilder.java
@@ -40,6 +40,7 @@
import org.apache.maven.api.model.Profile;
import org.apache.maven.api.model.Repository;
import org.apache.maven.api.model.Scm;
+import org.apache.maven.api.services.MavenException;
import org.apache.maven.api.services.ModelBuilder;
import org.apache.maven.api.services.ModelBuilderException;
import org.apache.maven.api.services.ModelBuilderRequest;
@@ -53,6 +54,45 @@
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
+/**
+ * Builds consumer POMs from project models, transforming them into a format
suitable for downstream consumers.
+ * <p>
+ * A consumer POM is a simplified version of a project's POM that is published
for consumption by other projects.
+ * It removes build-specific information and internal details while preserving
essential information like
+ * dependencies, repositories, and distribution management.
+ * <p>
+ * This builder applies two orthogonal transformations:
+ * <ul>
+ * <li><b>Dependency Flattening</b>: When enabled via {@code
maven.consumer.pom.flatten=true}, dependency management
+ * is flattened into direct dependencies for non-POM projects, and
mixins are removed.</li>
+ * <li><b>Model Version Handling</b>: When {@code
preserve.model.version=true} is set, the consumer POM
+ * maintains the original model version (4.2.0) instead of downgrading
to 4.0.0 for Maven 3 compatibility.
+ * This allows modern features like mixins to be preserved in the
consumer POM.</li>
+ * </ul>
+ * <p>
+ * <b>Mixin Handling</b>: Mixins are only supported in model version 4.2.0 or
later. If a POM contains mixins:
+ * <ul>
+ * <li>Setting {@code preserve.model.version=true} preserves them in the
consumer POM with model version 4.2.0</li>
+ * <li>Setting {@code maven.consumer.pom.flatten=true} removes them during
transformation</li>
+ * <li>Otherwise, an exception is thrown requiring one of the above options
or manual mixin removal</li>
+ * </ul>
+ * <p>
+ * <b>Dependency Filtering</b>: For non-POM projects with dependency
management, the builder:
+ * <ul>
+ * <li>Filters dependencies to include only those with transitive scopes
(compile/runtime)</li>
+ * <li>Applies managed dependency metadata (version, scope, optional flag,
exclusions) to direct dependencies</li>
+ * <li>Removes managed dependencies that are not used by direct
dependencies</li>
+ * <li>Retains only managed dependencies that appear in the resolved
dependency tree</li>
+ * </ul>
+ * <p>
+ * <b>Repository and Profile Pruning</b>: The consumer POM removal strategy:
+ * <ul>
+ * <li>Removes the central repository (only non-central repositories are
kept)</li>
+ * <li>Removes build, mailing lists, issue management, and other
build-specific information</li>
+ * <li>Removes profiles that have no activation, build, dependencies, or
properties</li>
+ * <li>Preserves relocation information in distribution management</li>
+ * </ul>
+ */
@Named
class DefaultConsumerPomBuilder implements PomBuilder {
private static final String BOM_PACKAGING = "bom";
@@ -80,6 +120,20 @@ public Model build(RepositorySystemSession session,
MavenProject project, ModelS
// Check if this is a BOM (original packaging is "bom")
boolean isBom = BOM_PACKAGING.equals(originalPackaging);
+ // Check if mixins are present without flattening enabled
+ if (!model.getMixins().isEmpty() && !flattenEnabled &&
!model.isPreserveModelVersion()) {
+ throw new MavenException("The consumer POM for "
+ + project.getId()
+ + " cannot be created because the POM contains mixins. "
+ + "Mixins are not supported in the default consumer POM
format. "
+ + "You have the following options to resolve this:" +
System.lineSeparator()
+ + " 1. Preserve the model version by setting
'preserve.model.version=true' to generate a consumer POM with
<modelVersion>4.2.0</modelVersion>, which supports mixins"
+ + System.lineSeparator()
+ + " 2. Enable flattening by setting the property
'maven.consumer.pom.flatten=true' to remove mixins during transformation"
+ + System.lineSeparator()
+ + " 3. Remove the mixins from your POM");
+ }
+
// Check if consumer POM flattening is disabled
if (!flattenEnabled) {
// When flattening is disabled, treat non-POM projects like parent
POMs
diff --git
a/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITgh11456MixinsConsumerPomTest.java
b/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITgh11456MixinsConsumerPomTest.java
new file mode 100644
index 0000000000..1d70146ced
--- /dev/null
+++
b/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITgh11456MixinsConsumerPomTest.java
@@ -0,0 +1,125 @@
+/*
+ * 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.io.Reader;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+import org.apache.maven.api.model.Model;
+import org.apache.maven.model.v4.MavenStaxReader;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * This is a test set for <a
href="https://github.com/apache/maven/issues/11456";>GH-11456</a>.
+ * @since 4.1.0
+ */
+class MavenITgh11456MixinsConsumerPomTest extends
AbstractMavenIntegrationTestCase {
+
+ /**
+ * Verify that Maven fails when a POM has non-empty mixins without
flattening being enabled.
+ */
+ @Test
+ void testMixinsWithoutFlattening() throws Exception {
+ Path basedir =
extractResources("/gh-11456-mixins-consumer-pom/non-flattened").toPath();
+
+ Verifier verifier = newVerifier(basedir.toString());
+ verifier.addCliArgument("-Dmaven.repo.local=" +
basedir.resolve("repo"));
+ verifier.addCliArgument("package");
+ try {
+ verifier.execute();
+ } catch (VerificationException e) {
+ // Expected to fail due to mixins without flattening
+ }
+
+ verifier.verifyTextInLog("cannot be created because the POM contains
mixins");
+ verifier.verifyTextInLog("maven.consumer.pom.flatten=true");
+ }
+
+ /**
+ * Verify that Maven succeeds when mixins are used with flattening enabled.
+ */
+ @Test
+ void testMixinsWithFlattening() throws Exception {
+ Path basedir =
extractResources("/gh-11456-mixins-consumer-pom/flattened").toPath();
+
+ Verifier verifier = newVerifier(basedir.toString());
+ verifier.addCliArgument("-Dmaven.repo.local=" +
basedir.resolve("repo").toString());
+ verifier.addCliArgument("package");
+ verifier.execute();
+ verifier.verifyErrorFreeLog();
+
+ // Verify consumer POM was created
+ Path consumerPom = basedir.resolve(Paths.get(
+ "target",
+ "project-local-repo",
+ "org.apache.maven.its.gh11456",
+ "flattened",
+ "1.0",
+ "flattened-1.0-consumer.pom"));
+ assertTrue(Files.exists(consumerPom), "consumer pom not found at " +
consumerPom);
+
+ // Verify mixins are removed from consumer POM
+ Model consumerPomModel;
+ try (Reader r = Files.newBufferedReader(consumerPom)) {
+ consumerPomModel = new MavenStaxReader().read(r);
+ }
+ assertTrue(
+ consumerPomModel.getMixins().isEmpty(),
+ "Mixins should be removed from consumer POM when flattening is
enabled");
+ }
+
+ /**
+ * Verify that Maven succeeds when mixins are used with flattening enabled.
+ */
+ @Test
+ void testMixinsWithPreserveModelVersion() throws Exception {
+ Path basedir =
extractResources("/gh-11456-mixins-consumer-pom/preserve-model-version").toPath();
+
+ Verifier verifier = newVerifier(basedir.toString());
+ verifier.addCliArgument("-Dmaven.repo.local=" +
basedir.resolve("repo").toString());
+ verifier.addCliArgument("package");
+ verifier.execute();
+ verifier.verifyErrorFreeLog();
+
+ // Verify consumer POM was created
+ Path consumerPom = basedir.resolve(Paths.get(
+ "target",
+ "project-local-repo",
+ "org.apache.maven.its.gh11456",
+ "preserve-model-version",
+ "1.0",
+ "preserve-model-version-1.0-consumer.pom"));
+ assertTrue(Files.exists(consumerPom), "consumer pom not found at " +
consumerPom);
+
+ // Verify mixins are removed from consumer POM
+ Model consumerPomModel;
+ try (Reader r = Files.newBufferedReader(consumerPom)) {
+ consumerPomModel = new MavenStaxReader().read(r);
+ }
+ assertFalse(
+ consumerPomModel.getMixins().isEmpty(),
+ "Mixins should be kept in consumer POM when
preserveModelVersion is enabled");
+ }
+}
+
diff --git
a/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITmng5102MixinsTest.java
b/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITmng5102MixinsTest.java
index 0200c5d828..2ccc8d4e36 100644
---
a/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITmng5102MixinsTest.java
+++
b/its/core-it-suite/src/test/java/org/apache/maven/it/MavenITmng5102MixinsTest.java
@@ -90,7 +90,7 @@ public void testWithGav() throws Exception {
verifier = newVerifier(new File(testDir, "project").getAbsolutePath());
verifier.setAutoclean(false);
verifier.deleteDirectory("target");
- verifier.addCliArgument("install");
+ verifier.addCliArguments("install", "-Dmaven.consumer.pom.flatten");
verifier.execute();
verifier.verifyErrorFreeLog();
@@ -126,7 +126,7 @@ public void testWithClassifier() throws Exception {
verifier = newVerifier(new File(testDir, "project").getAbsolutePath());
verifier.setAutoclean(false);
verifier.deleteDirectory("target");
- verifier.addCliArgument("install");
+ verifier.addCliArguments("install", "-Dmaven.consumer.pom.flatten");
verifier.execute();
verifier.verifyErrorFreeLog();
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/.mvn/.gitkeep
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/.mvn/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/.mvn/maven-user.properties
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/.mvn/maven-user.properties
new file mode 100644
index 0000000000..c90ca4d2f0
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/.mvn/maven-user.properties
@@ -0,0 +1 @@
+maven.consumer.pom.flatten=true
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/pom.xml
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/pom.xml
new file mode 100644
index 0000000000..20bb8dcffd
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/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/4.2.0";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; root="true"
xsi:schemaLocation="http://maven.apache.org/POM/4.2.0
http://maven.apache.org/xsd/maven-4.2.0.xsd";>
+ <modelVersion>4.2.0</modelVersion>
+ <groupId>org.apache.maven.its.gh11456</groupId>
+ <artifactId>flattened</artifactId>
+ <version>1.0</version>
+ <packaging>jar</packaging>
+
+ <name>Maven Integration Test :: GH-11456 :: Mixins with Consumer POM
Flattened</name>
+ <description>Test that Maven succeeds when mixins are used with flattening
enabled.</description>
+
+ <mixins>
+ <mixin>
+ <groupId>org.apache.maven.its.gh11456</groupId>
+ <artifactId>test-mixin-flattened</artifactId>
+ <version>1.0</version>
+ </mixin>
+ </mixins>
+</project>
+
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/repo/org/apache/maven/its/gh11456/test-mixin-flattened/1.0/test-mixin-flattened-1.0.pom
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/repo/org/apache/maven/its/gh11456/test-mixin-flattened/1.0/test-mixin-flattened-1.0.pom
new file mode 100644
index 0000000000..10f66e8383
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/repo/org/apache/maven/its/gh11456/test-mixin-flattened/1.0/test-mixin-flattened-1.0.pom
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.2.0";>
+ <modelVersion>4.2.0</modelVersion>
+ <groupId>org.apache.maven.its.gh11456</groupId>
+ <artifactId>test-mixin-flattened</artifactId>
+ <version>1.0</version>
+ <packaging>pom</packaging>
+
+ <properties>
+ <test.property>from-mixin-flattened</test.property>
+ </properties>
+</project>
+
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/src/main/java/Test.java
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/src/main/java/Test.java
new file mode 100644
index 0000000000..fccbf31fcd
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/flattened/src/main/java/Test.java
@@ -0,0 +1,20 @@
+/*
+ * 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.
+ */
+public class Test {}
+
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/.mvn/.gitkeep
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/.mvn/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/pom.xml
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/pom.xml
new file mode 100644
index 0000000000..693c612c72
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/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/4.2.0";
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; root="true"
xsi:schemaLocation="http://maven.apache.org/POM/4.2.0
http://maven.apache.org/xsd/maven-4.2.0.xsd";>
+ <modelVersion>4.2.0</modelVersion>
+ <groupId>org.apache.maven.its.gh11456</groupId>
+ <artifactId>non-flattened</artifactId>
+ <version>1.0</version>
+ <packaging>jar</packaging>
+
+ <name>Maven Integration Test :: GH-11456 :: Mixins with Consumer POM</name>
+ <description>Test that Maven fails when mixins are used without flattening
enabled.</description>
+
+ <mixins>
+ <mixin>
+ <groupId>org.apache.maven.its.gh11456</groupId>
+ <artifactId>test-mixin</artifactId>
+ <version>1.0</version>
+ </mixin>
+ </mixins>
+</project>
+
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/repo/org/apache/maven/its/gh11456/test-mixin/1.0/test-mixin-1.0.pom
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/repo/org/apache/maven/its/gh11456/test-mixin/1.0/test-mixin-1.0.pom
new file mode 100644
index 0000000000..d7d04b702a
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/repo/org/apache/maven/its/gh11456/test-mixin/1.0/test-mixin-1.0.pom
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.2.0";>
+ <modelVersion>4.2.0</modelVersion>
+ <groupId>org.apache.maven.its.gh11456</groupId>
+ <artifactId>test-mixin</artifactId>
+ <version>1.0</version>
+ <packaging>pom</packaging>
+
+ <properties>
+ <test.property>from-mixin</test.property>
+ </properties>
+</project>
+
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/src/main/java/Test.java
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/src/main/java/Test.java
new file mode 100644
index 0000000000..fccbf31fcd
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/non-flattened/src/main/java/Test.java
@@ -0,0 +1,20 @@
+/*
+ * 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.
+ */
+public class Test {}
+
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/.mvn/.gitkeep
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/.mvn/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/.mvn/maven.properties
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/.mvn/maven.properties
new file mode 100644
index 0000000000..c90ca4d2f0
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/.mvn/maven.properties
@@ -0,0 +1 @@
+maven.consumer.pom.flatten=true
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/pom.xml
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/pom.xml
new file mode 100644
index 0000000000..b4f4ef6813
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/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/4.2.0"; root="true"
preserve.model.version="true">
+ <modelVersion>4.2.0</modelVersion>
+ <groupId>org.apache.maven.its.gh11456</groupId>
+ <artifactId>preserve-model-version</artifactId>
+ <version>1.0</version>
+ <packaging>jar</packaging>
+
+ <name>Maven Integration Test :: GH-11456 :: Mixins with Consumer POM
Preserving modelVersion</name>
+ <description>Test that Maven succeeds when mixins are used when
preserveModelVersion is true.</description>
+
+ <mixins>
+ <mixin>
+ <groupId>org.apache.maven.its.gh11456</groupId>
+ <artifactId>test-mixin-flattened</artifactId>
+ <version>1.0</version>
+ </mixin>
+ </mixins>
+</project>
+
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/repo/org/apache/maven/its/gh11456/test-mixin-flattened/1.0/test-mixin-flattened-1.0.pom
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/repo/org/apache/maven/its/gh11456/test-mixin-flattened/1.0/test-mixin-flattened-1.0.pom
new file mode 100644
index 0000000000..10f66e8383
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/repo/org/apache/maven/its/gh11456/test-mixin-flattened/1.0/test-mixin-flattened-1.0.pom
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.2.0";>
+ <modelVersion>4.2.0</modelVersion>
+ <groupId>org.apache.maven.its.gh11456</groupId>
+ <artifactId>test-mixin-flattened</artifactId>
+ <version>1.0</version>
+ <packaging>pom</packaging>
+
+ <properties>
+ <test.property>from-mixin-flattened</test.property>
+ </properties>
+</project>
+
diff --git
a/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/src/main/java/Test.java
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/src/main/java/Test.java
new file mode 100644
index 0000000000..fccbf31fcd
--- /dev/null
+++
b/its/core-it-suite/src/test/resources/gh-11456-mixins-consumer-pom/preserve-model-version/src/main/java/Test.java
@@ -0,0 +1,20 @@
+/*
+ * 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.
+ */
+public class Test {}
+
