The problem seems to be that an entirely new instance of ClassPathProviderImpl is pulled out of the hat (project lookup) in projectClosed(). That in turn creates new bootCp.


my first thought was that https://hg.netbeans.org/core-main/rev/1cfe2b43fe32 could be responsible, but backing up the revision had no visible effect. 

The problem is buried deep in project and general lookup infrastructure? jesse, yarda, any idea?

I think it is a bug in LazyLookupProviders.

I can reproduce the problem. I suspect the fault lies in the multiple service interfaces implemented by ClassPathProviderImpl, and/or the multilevel lookup wrapped used by Maven projects.

Unfortunately I am unable to reproduce in a unit test, even one loading CPPI specifically.

#205533 was resolved to be unresolved - sometimes >1 instance of a service is created and there is no known way to prevent that. (Meaning that GlobalPathRegistry just has to quietly ignore the problem.) However that was supposed to be random, whereas this seems to happen quite consistently.

I can fix this bug, but at the cost of introducing a memory leak:

diff --git a/projectapi/src/org/netbeans/modules/projectapi/LazyLookupProviders.java b/projectapi/src/org/netbeans/modules/projectapi/LazyLookupProviders.java
--- a/projectapi/src/org/netbeans/modules/projectapi/LazyLookupProviders.java
+++ b/projectapi/src/org/netbeans/modules/projectapi/LazyLookupProviders.java
@@ -82,8 +82,11 @@
      */
     public static LookupProvider forProjectServiceProvider(final Map<String,Object> attrs) throws ClassNotFoundException {
         return new LookupProvider() {
-            public Lookup createAdditionalLookup(final Lookup lkp) {
-                return new ProxyLookup() {
+            final Map<Lookup,Lookup> added = new WeakHashMap<Lookup,Lookup>();
+            @Override public synchronized Lookup createAdditionalLookup(final Lookup lkp) {
+                Lookup result = added.get(lkp);
+                if (result == null) {
+                    result = new ProxyLookup() {
                     Collection<String> serviceNames = Arrays.asList(((String) attrs.get("service")).split(",")); // NOI18N
                     @Override protected void beforeLookup(Template<?> template) {
                         safeToLoad();
@@ -128,6 +131,9 @@
                         }
                     }
                 };
+                added.put(lkp, result);
+                }
+                return result;
             }
         };
     }

core-main #1ef82eb26a3b

Integrated into 'main-golden', will be available in build *201204040400* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
Changeset: http://hg.netbeans.org/main-golden/rev/1ef82eb26a3b
User: Jesse Glick <jglick@netbeans.org>
Log: #209815: IAE from GlobalPathRegistry.unregister; multiple ClassPathProviderImpl's created for one project
Not fixing root problem - multiple CPPIs per Project - but working around symptom in GPR.

Integrated into 'main-golden', will be available in build *201204060400* on http://bits.netbeans.org/dev/nightly/ (upload may still be in progress)
Changeset: http://hg.netbeans.org/main-golden/rev/631a163bf56e
User: Jesse Glick <jglick@netbeans.org>
Log: A bit more logging related to #209815.