From ce7be0ef4955119c06fd7c621a6d12897bdd9656 Mon Sep 17 00:00:00 2001
From: Stepan Hrbacek <stepan.hrbacek@solarwinds.com>
Date: Sun, 5 Jan 2020 20:16:01 +0100
Subject: [PATCH] Clone projects in MavenSession.clone()

Each build session will then have its own copy of MavenProject objects
and cannot be influenced, for example, get determining compile classpath
by other running build threads.
---
 .../apache/maven/execution/MavenSession.java  | 35 +++++++++++++++++--
 1 file changed, 32 insertions(+), 3 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 5b56df36d003..cc361ec79505 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
@@ -21,6 +21,8 @@
 
 import java.io.File;
 import java.util.Arrays;
+import java.util.ArrayList;
+import java.util.Collections;
 import java.util.Date;
 import java.util.List;
 import java.util.Map;
@@ -79,7 +81,7 @@ public class MavenSession
         new ConcurrentHashMap<>();
 
 
-    public void setProjects( List<MavenProject> projects )
+    public synchronized void setProjects( List<MavenProject> projects )
     {
         if ( !projects.isEmpty() )
         {
@@ -239,7 +241,10 @@ public MavenSession clone()
     {
         try
         {
-            return (MavenSession) super.clone();
+            MavenSession thisClone = (MavenSession) super.clone();
+            thisClone.setProjects( getProjectsClone() );
+
+            return thisClone;
         }
         catch ( CloneNotSupportedException e )
         {
@@ -247,6 +252,30 @@ public MavenSession clone()
         }
     }
 
+    private synchronized List<MavenProject> getProjectsClone()
+    {
+        if ( projects == null )
+        {
+            return null;
+        }
+        else
+        {
+            if ( projects.isEmpty() )
+            {
+                return Collections.emptyList();
+            }
+            else
+            {
+                List<MavenProject> clonedProjects = new ArrayList<>( projects.size() );
+                for ( MavenProject project : projects )
+                {
+                    clonedProjects.add( project.clone() );
+                }
+                return clonedProjects;
+            }
+        }
+    }
+
     public Date getStartTime()
     {
         return request.getStartTime();
@@ -302,7 +331,7 @@ public Map<String, MavenProject> getProjectMap()
     {
         return projectMap;
     }
-    
+
     @Deprecated
     public MavenSession( PlexusContainer container, RepositorySystemSession repositorySession,
                          MavenExecutionRequest request, MavenExecutionResult result )