From 9e65a7a761cd064e274931197533326c48594f4b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christoph=20L=C3=A4ubrich?= <christoph@laeubi-soft.de>
Date: Sat, 29 Jan 2022 12:08:50 +0100
Subject: [PATCH 1/2] MNG-7401 - Make MavenSession#getCurrentProject() using a
 thread local

This allows multiple threads to set/get the current project on the same
session object while still having clones maintain there own state.
---
 .../apache/maven/execution/MavenSession.java  | 22 ++++++++++++-------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/maven-core/src/main/java/org/apache/maven/execution/MavenSession.java b/maven-core/src/main/java/org/apache/maven/execution/MavenSession.java
index c2f0c89e862e..cc6d0ece92bb 100644
--- a/maven-core/src/main/java/org/apache/maven/execution/MavenSession.java
+++ b/maven-core/src/main/java/org/apache/maven/execution/MavenSession.java
@@ -55,7 +55,7 @@ public class MavenSession
 
     private Properties executionProperties;
 
-    private MavenProject currentProject;
+    private ThreadLocal<MavenProject> currentProject = new ThreadLocal<>();
 
     /**
      * These projects have already been topologically sorted in the {@link org.apache.maven.Maven} component before
@@ -90,20 +90,21 @@ public void setProjects( List<MavenProject> projects )
     {
         if ( !projects.isEmpty() )
         {
-            this.currentProject = projects.get( 0 );
-            this.topLevelProject = currentProject;
+            MavenProject first = projects.get( 0 );
+            this.topLevelProject = first;
+            this.currentProject = ThreadLocal.withInitial( () -> first );
             for ( MavenProject project : projects )
             {
                 if ( project.isExecutionRoot() )
                 {
-                    topLevelProject = project;
+                    this.topLevelProject = project;
                     break;
                 }
             }
         }
         else
         {
-            this.currentProject = null;
+            this.currentProject = new ThreadLocal<>();
             this.topLevelProject = null;
         }
         this.projects = projects;
@@ -164,12 +165,12 @@ public MavenExecutionRequest getRequest()
 
     public void setCurrentProject( MavenProject currentProject )
     {
-        this.currentProject = currentProject;
+        this.currentProject.set( currentProject );
     }
 
     public MavenProject getCurrentProject()
     {
-        return currentProject;
+        return currentProject.get();
     }
 
     public ProjectBuildingRequest getProjectBuildingRequest()
@@ -240,7 +241,12 @@ public MavenSession clone()
     {
         try
         {
-            return (MavenSession) super.clone();
+            MavenSession clone = (MavenSession) super.clone();
+            // the default must become the current project of the thread that clones this
+            MavenProject current = getCurrentProject();
+            // we replace the thread local of the clone to prevent write through and enforce the new default value
+            clone.currentProject = ThreadLocal.withInitial( () -> current );
+            return clone;
         }
         catch ( CloneNotSupportedException e )
         {

From 49365a657c6e926c53e58e95d0786c1d30c59570 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christoph=20L=C3=A4ubrich?= <christoph@laeubi-soft.de>
Date: Sat, 29 Jan 2022 12:50:51 +0100
Subject: [PATCH 2/2] No more need to clone the session

---
 .../lifecycle/internal/BuildListCalculator.java     | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/maven-core/src/main/java/org/apache/maven/lifecycle/internal/BuildListCalculator.java b/maven-core/src/main/java/org/apache/maven/lifecycle/internal/BuildListCalculator.java
index 9000c9301eae..d61279d7f969 100644
--- a/maven-core/src/main/java/org/apache/maven/lifecycle/internal/BuildListCalculator.java
+++ b/maven-core/src/main/java/org/apache/maven/lifecycle/internal/BuildListCalculator.java
@@ -61,9 +61,16 @@ public ProjectBuildList calculateProjectBuilds( MavenSession session, List<TaskS
             for ( MavenProject project : projects )
             {
                 BuilderCommon.attachToThread( project ); // Not totally sure if this is needed for anything
-                MavenSession copiedSession = session.clone();
-                copiedSession.setCurrentProject( project );
-                projectBuilds.add( new ProjectSegment( project, taskSegment, copiedSession ) );
+                MavenProject currentProject = session.getCurrentProject();
+                try
+                {
+                    session.setCurrentProject( project );
+                    projectBuilds.add( new ProjectSegment( project, taskSegment, session ) );
+                }
+                finally
+                {
+                    session.setCurrentProject( currentProject );
+                }
             }
         }
         return new ProjectBuildList( projectBuilds );