feat: flatten non-BOM artifacts
This change introduces a new execution of the Flatten Maven Plugin for non-BOM modules, aimed at simplifying their published POMs while preserving important metadata and build integrity.
### Key changes
* Applies `clean` mode, removing most optional POM elements.
* Retains key elements:
* `<name>`, `<description>`, and `<url>` are expanded to preserve meaningful metadata and prevent undesirable URL inheritance (i.e., appending `artifactId` to the parent URL).
* `<license>` is preserved in each module for clarity and utility.
* Keeps the `<parent>` element so modules continue to inherit metadata and `dependencyManagement` from `log4j-bom` and their direct ancestors.
* `<properties>` are removed, but `<dependencies>` and `<dependencyManagement>` are retained with interpolated values to avoid unresolved variables in the flattened POMs.
### Differences from the `clean` mode
* Keeps `name` and `description` per module to aid discoverability.
* Delegates all contact and project metadata (organization, developers, mailing lists, SCM, issue tracker, CI config, etc.) to the centralized `log4j-bom` POM.
* Preserves `dependencyManagement` sections by interpolating versions, rather than removing them.
* Retains non-transitive scopes (`provided`, `test`) to expose compile/test-time dependencies, even if consumers don't require them.
This flattening strategy reduces noise in published POMs while maintaining enough structure for clarity and downstream tool compatibility.
diff --git a/log4j-mongodb/pom.xml b/log4j-mongodb/pom.xml
index 452ac0a..7ccc14f 100644
--- a/log4j-mongodb/pom.xml
+++ b/log4j-mongodb/pom.xml
@@ -128,13 +128,6 @@
<configuration>
<skip>true</skip>
</configuration>
- <dependencies>
- <dependency>
- <groupId>org.junit.jupiter</groupId>
- <artifactId>junit-jupiter-engine</artifactId>
- <version>${junit-jupiter.version}</version>
- </dependency>
- </dependencies>
</plugin>
</plugins>
diff --git a/log4j-parent/pom.xml b/log4j-parent/pom.xml
index 22802a5..48027a3 100644
--- a/log4j-parent/pom.xml
+++ b/log4j-parent/pom.xml
@@ -1140,6 +1140,52 @@
</executions>
</plugin>
+ <!--
+ ~ Drop the <build> section from flattened POMs.
+ ~ Keeps the consumer POM minimal and prevents flattened build-only properties
+ ~ (e.g., `error-prone.version`) from causing resolution problems to users.
+ ~
+ ~ Ref: https://github.com/apache/logging-log4j2/issues/3779
+ -->
+ <plugin>
+ <groupId>org.codehaus.mojo</groupId>
+ <artifactId>flatten-maven-plugin</artifactId>
+ <executions>
+ <!-- First use the special `resolveCiFriendliesOnly` mode to replace the special `${revision}` property with the actual version.
+ This is necessary because `flatten` mode does not support `ci-friendly` versions. -->
+ <execution>
+ <id>flatten-revision</id>
+ </execution>
+ <execution>
+ <id>flatten</id>
+ <goals>
+ <goal>flatten</goal>
+ </goals>
+ <phase>process-resources</phase>
+ <configuration>
+ <!-- Use 'clean' as a base, then selectively retain key elements -->
+ <flattenMode>clean</flattenMode>
+ <pomElements>
+ <!-- Keep parent to maintain inheritance from log4j-bom and ancestors -->
+ <parent>keep</parent>
+
+ <!-- Retain meaningful module metadata -->
+ <name>expand</name>
+ <description>expand</description>
+
+ <!-- Expand URL to prevent default behavior of appending artifactId -->
+ <url>expand</url>
+
+ <!-- Keep dependencyManagement and dependencies, interpolating property-based versions -->
+ <dependencyManagement>interpolate</dependencyManagement>
+ <dependencies>interpolate</dependencies>
+ </pomElements>
+ </configuration>
+ </execution>
+
+ </executions>
+ </plugin>
+
</plugins>
</build>
diff --git a/pom.xml b/pom.xml
index df51f7d..80ab710 100644
--- a/pom.xml
+++ b/pom.xml
@@ -630,6 +630,37 @@
</configuration>
</plugin>
+ <!--
+ ~ Memento rules to remove overrides from child modules, whenever the changes are moved to `logging-parent`.
+ ~
+ ~ When empty, please comment this execution out, but do not delete it!
+ -->
+ <plugin>
+ <groupId>org.apache.maven.plugins</groupId>
+ <artifactId>maven-enforcer-plugin</artifactId>
+ <executions>
+ <execution>
+ <id>remove-overrides</id>
+ <goals>
+ <goal>enforce</goal>
+ </goals>
+ <!-- Wait until we retrieve `parent.version` property in `build-helper-maven-plugin` below -->
+ <phase>initialize</phase>
+ <inherited>false</inherited>
+ <configuration>
+ <rules>
+ <requireProperty>
+ <property>parent.version</property>
+ <regex>12\.1\.1</regex>
+ <regexMessage>Remember to remove overrides from child modules, whenever the changes are moved to `logging-parent`:
+ * Remove the override `flatten-maven-plugin` configuration from `log4j-parent/pom.xml`.</regexMessage>
+ </requireProperty>
+ </rules>
+ </configuration>
+ </execution>
+ </executions>
+ </plugin>
+
<!-- ███████ ████████ █████ ██████ ████████ ███████ ██ ████████ ███████
██ ██ ██ ██ ██ ██ ██ ██ ██ ██ ██ ██
███████ ██ ███████ ██████ ██ ███████ ██ ██ █████
@@ -657,6 +688,21 @@
<locale>en_US</locale>
</configuration>
</execution>
+ <!-- Used by `maven-enforcer-plugin` above -->
+ <execution>
+ <id>capture-parent-version</id>
+ <goals>
+ <goal>regex-property</goal>
+ </goals>
+ <phase>validate</phase>
+ <inherited>false</inherited>
+ <configuration>
+ <name>parent.version</name>
+ <value>${project.parent.version}</value>
+ <regex>^(.+)$</regex>
+ <replacement>$1</replacement>
+ </configuration>
+ </execution>
</executions>
</plugin>
