Revert "Merge pull request #979 from ascopes/task/flatten-poms"

This reverts commit aeecace, reversing
changes made to 4aa32ed.

This is reverted due to the following error when deploying artifacts:

[INFO] 1/17 prepare:check-poms
[INFO] 2/17 prepare:scm-check-modifications
[INFO] Verifying that there are no local modifications...
[INFO]   ignoring changes on: **/pom.xml.releaseBackup, **/pom.xml.next, **/pom.xml.tag, **/pom.xml.branch, **/release.properties, **/pom.xml.backup
[WARNING] Ignoring unrecognized line: ?? release.properties
[INFO] 3/17 prepare:check-dependency-snapshots
[INFO] Checking dependencies and plugins for snapshots ...
[INFO] 4/17 prepare:create-backup-poms
[INFO] Creating pom.xml backup with .releaseBackup suffix
[INFO] 5/17 prepare:map-release-versions
[INFO] 6/17 prepare:input-variables
[INFO] 7/17 prepare:map-development-versions
[INFO] 8/17 prepare:rewrite-poms-for-release
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary for Protobuf Maven Plugin Parent 5.1.3-SNAPSHOT:
[INFO]
[INFO] Protobuf Maven Plugin Parent ....................... FAILURE [  1.537 s]
[INFO] Protobuf Maven Plugin .............................. SUCCESS [07:29 min]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  07:39 min (Wall Clock)
[INFO] Finished at: 2026-04-10T12:09:34Z
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-release-plugin:3.3.1:prepare (default-cli) on project protobuf-maven-plugin-parent: Execution default-cli of goal org.apache.maven.plugins:maven-release-plugin:3.3.1:prepare failed: Cannot invoke "org.apache.maven.model.Parent.getVersion()" because the return value of "org.apache.maven.model.Model.getParent()" is null -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-release-plugin:3.3.1:prepare (default-cli) on project protobuf-maven-plugin-parent: Execution default-cli of goal org.apache.maven.plugins:maven-release-plugin:3.3.1:prepare failed: Cannot invoke "org.apache.maven.model.Parent.getVersion()" because the return value of "org.apache.maven.model.Model.getParent()" is null
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2 (MojoExecutor.java:333)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute (MojoExecutor.java:316)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:212)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:174)
    at org.apache.maven.lifecycle.internal.MojoExecutor.access$000 (MojoExecutor.java:75)
    at org.apache.maven.lifecycle.internal.MojoExecutor$1.run (MojoExecutor.java:162)
    at org.apache.maven.plugin.DefaultMojosExecutionStrategy.execute (DefaultMojosExecutionStrategy.java:39)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:159)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:105)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:193)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:180)
    at java.util.concurrent.FutureTask.run (FutureTask.java:328)
    at java.util.concurrent.Executors$RunnableAdapter.call (Executors.java:545)
    at java.util.concurrent.FutureTask.run (FutureTask.java:328)
    at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1090)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:614)
    at java.lang.Thread.run (Thread.java:1474)
Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default-cli of goal org.apache.maven.plugins:maven-release-plugin:3.3.1:prepare failed: Cannot invoke "org.apache.maven.model.Parent.getVersion()" because the return value of "org.apache.maven.model.Model.getParent()" is null
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:133)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2 (MojoExecutor.java:328)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute (MojoExecutor.java:316)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:212)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:174)
    at org.apache.maven.lifecycle.internal.MojoExecutor.access$000 (MojoExecutor.java:75)
    at org.apache.maven.lifecycle.internal.MojoExecutor$1.run (MojoExecutor.java:162)
    at org.apache.maven.plugin.DefaultMojosExecutionStrategy.execute (DefaultMojosExecutionStrategy.java:39)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:159)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:105)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:193)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:180)
    at java.util.concurrent.FutureTask.run (FutureTask.java:328)
    at java.util.concurrent.Executors$RunnableAdapter.call (Executors.java:545)
    at java.util.concurrent.FutureTask.run (FutureTask.java:328)
    at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1090)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:614)
    at java.lang.Thread.run (Thread.java:1474)
Caused by: java.lang.NullPointerException: Cannot invoke "org.apache.maven.model.Parent.getVersion()" because the return value of "org.apache.maven.model.Model.getParent()" is null
    at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.rewriteParent (AbstractRewritePomsPhase.java:480)
    at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.transformDocument (AbstractRewritePomsPhase.java:284)
    at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.transformProject (AbstractRewritePomsPhase.java:260)
    at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.transform (AbstractRewritePomsPhase.java:222)
    at org.apache.maven.shared.release.phase.AbstractRewritePomsPhase.execute (AbstractRewritePomsPhase.java:158)
    at org.apache.maven.shared.release.DefaultReleaseManager.prepare (DefaultReleaseManager.java:193)
    at org.apache.maven.shared.release.DefaultReleaseManager.prepare (DefaultReleaseManager.java:110)
    at org.apache.maven.plugins.release.PrepareReleaseMojo.prepareRelease (PrepareReleaseMojo.java:439)
    at org.apache.maven.plugins.release.PrepareReleaseMojo.execute (PrepareReleaseMojo.java:376)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:126)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2 (MojoExecutor.java:328)
    at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute (MojoExecutor.java:316)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:212)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:174)
    at org.apache.maven.lifecycle.internal.MojoExecutor.access$000 (MojoExecutor.java:75)
    at org.apache.maven.lifecycle.internal.MojoExecutor$1.run (MojoExecutor.java:162)
    at org.apache.maven.plugin.DefaultMojosExecutionStrategy.execute (DefaultMojosExecutionStrategy.java:39)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:159)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:105)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:193)
    at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:180)
    at java.util.concurrent.FutureTask.run (FutureTask.java:328)
    at java.util.concurrent.Executors$RunnableAdapter.call (Executors.java:545)
    at java.util.concurrent.FutureTask.run (FutureTask.java:328)
    at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1090)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:614)
    at java.lang.Thread.run (Thread.java:1474)

Author: ascopes

.gitignore

@@ -11,9 +11,6 @@ target/
 # JVM agent descriptors
 .attach*
 
-# Flattened POMs
-.flattened-pom.xml
-
 # Version backups after running ./mvnw versions:set
 pom.xml.versionsBackup
 

pom.xml

@@ -113,7 +113,6 @@
 
     <!-- Plugins -->
     <central-publishing-maven-plugin.version>0.10.0</central-publishing-maven-plugin.version>
-    <flatten-maven-plugin.version>1.7.3</flatten-maven-plugin.version>
     <jacoco-maven-plugin.version>0.8.14</jacoco-maven-plugin.version>
     <license-maven-plugin.version>5.0.0</license-maven-plugin.version>
     <maven-assembly-plugin.version>3.8.0</maven-assembly-plugin.version>
@@ -759,38 +758,6 @@
         <artifactId>maven-release-plugin</artifactId>
       </plugin>
 
-      <plugin>
-        <!-- Produces a simplified POM for deployments. -->
-        <groupId>org.codehaus.mojo</groupId>
-        <artifactId>flatten-maven-plugin</artifactId>
-        <version>${flatten-maven-plugin.version}</version>
-
-        <configuration>
-          <!-- Keep everything that is required for publishing to Maven Central
-               successfully. This includes the required POM metadata we should be keeping
-               for validation to succeed. -->
-          <flattenMode>ossrh</flattenMode>
-        </configuration>
-
-        <executions>
-          <execution>
-            <id>clean-flattened-pom</id>
-            <phase>clean</phase>
-            <goals>
-              <goal>clean</goal>
-            </goals>
-          </execution>
-
-          <execution>
-            <id>flatten-pom</id>
-            <phase>prepare-package</phase>
-            <goals>
-              <goal>flatten</goal>
-            </goals>
-          </execution>
-        </executions>
-      </plugin>
-
       <plugin>
         <!--
             Intercepts the default deploy phase and replaces it with goals that