NPE Error when trying to install incubator plug-ins (including workaround)

[jonahgraham]

When trying to install most any Incubator plug-ins into Trace Compass an NPE error is hit that prevents proceeding. The underlying bug is eclipse-equinox/p2#1050. Here I provide a workaround for incubator users.

The Problem

When installing, if Py4J is a required bundle, the trust dialog is shown, but the "Trust Selected" button never gets enabled. Pressing some buttons can generate NPEs too.

NPE stacktrace

!ENTRY org.eclipse.jface 4 2 2026-03-11 14:28:15.411
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.jface".
!STACK 0
java.lang.NullPointerException: Cannot invoke "org.eclipse.jface.viewers.TreeNode.getChildren()" because "treeNode" is null
        at org.eclipse.equinox.internal.p2.ui.dialogs.TrustAuthorityDialog.getAllChildren(TrustAuthorityDialog.java:817)
        at org.eclipse.equinox.internal.p2.ui.dialogs.TrustAuthorityDialog.getAllChildren(TrustAuthorityDialog.java:812)
        at org.eclipse.equinox.internal.p2.ui.dialogs.TrustAuthorityDialog.lambda$3(TrustAuthorityDialog.java:261)
        at org.eclipse.jface.viewers.CheckboxTreeViewer$1.run(CheckboxTreeViewer.java:168)
        at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:47)
        at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:167)
        at org.eclipse.jface.viewers.CheckboxTreeViewer.fireCheckStateChanged(CheckboxTreeViewer.java:165)
        at org.eclipse.jface.viewers.CheckboxTreeViewer.handleSelect(CheckboxTreeViewer.java:295)
        at org.eclipse.jface.viewers.StructuredViewer$4.widgetSelected(StructuredViewer.java:1198)
        at org.eclipse.jface.util.OpenStrategy.fireSelectionEvent(OpenStrategy.java:262)
        at org.eclipse.jface.util.OpenStrategy$1.handleEvent(OpenStrategy.java:420)
        at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:91)
        at org.eclipse.swt.widgets.Display.sendEvent(Display.java:5884)
        at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1656)
        at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:5099)
        at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4540)
        at org.eclipse.jface.window.Window.runEventLoop(Window.java:823)
        at org.eclipse.jface.window.Window.open(Window.java:799)
        at org.eclipse.equinox.internal.p2.ui.ValidationDialogServiceUI.lambda$18(ValidationDialogServiceUI.java:469)
        at org.eclipse.ui.internal.PendingSyncExec.run(PendingSyncExec.java:68)
        at org.eclipse.ui.internal.UILockListener.doPendingWork(UILockListener.java:166)
        at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:40)
        at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:132)
        at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:5074)
        at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4543)
        at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1151)
        at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
        at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1042)
        at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:153)
        at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:678)
        at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
        at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:583)
        at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:173)
        at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:185)
        at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:219)
        at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:149)
        at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:115)
        at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:467)
        at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:298)
        at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
        at java.base/java.lang.reflect.Method.invoke(Method.java:580)
        at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:627)
        at org.eclipse.equinox.launcher.Main.basicRun(Main.java:575)
        at org.eclipse.equinox.launcher.Main.run(Main.java:1431)
        at org.eclipse.equinox.launcher.Main.main(Main.java:1403)

Workaround

The workaround is to manually install Py4J manually first:

1. Add https://eclipse.py4j.org/ (Trailing slash is critical) to Available Software Sites. (If you already have the non / version, delete it and reopen preferences):

2. From Help -> Install new software, choose the py4j site and install Py4J (complete the wizard):

3. After Restart, do Help -> Install new software again and install the incubator components normally.