Cannot invoke "org.eclipse.swt.browser.Browser.setRedraw(boolean)" because "this.fBrowser" is null

[laeubi]

!ENTRY org.eclipse.ui 4 0 2024-10-27 18:52:37.949
!MESSAGE Unhandled event loop exception
!STACK 0
java.lang.NullPointerException: Cannot invoke "org.eclipse.swt.browser.Browser.setRedraw(boolean)" because "this.fBrowser" is null
	at org.eclipse.jface.internal.text.html.BrowserInformationControl.setSize(BrowserInformationControl.java:378)
	at org.eclipse.lsp4e.operations.hover.FocusableBrowserInformationControl.lambda$0(FocusableBrowserInformationControl.java:121)
	at org.eclipse.swt.browser.ProgressListener$2.completed(ProgressListener.java:98)
	at org.eclipse.swt.browser.WebKit.lambda$7(WebKit.java:1765)
	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:5040)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:4520)
	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:639)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:546)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:173)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:152)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:208)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:143)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:109)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:439)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:271)
	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:668)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:605)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1481)
	at org.eclipse.equinox.launcher.Main.main(Main.java:1454)

Happens on

Version: 2024-12 M2 (4.34.0 M2)
Build id: 20241024-0621

[jukzi]

The error seems to be in org.eclipse.lsp4e.operations.hover.FocusableBrowserInformationControl
Closing at not platform. Please report to https://github.com/eclipse/lsp4e, would also help if you add information how to reproduce and which OS.

[laeubi]

The error seems to be in org.eclipse.lsp4e.operations.hover.FocusableBrowserInformationControl

Why does it seem to? The last stackframe is

org.eclipse.jface.internal.text.html.BrowserInformationControl.setSize(BrowserInformationControl.java:378)

what has nothing to do with lsp4e.

As I have never seen such error before updating Eclipse from M1 > M2 I highly doubt it has something to do with lsp4e.

[Phillipus]

Looking at FocusableBrowserInformationControl and BrowserInformationControl it seems that fBrowser will be null when BrowserInformationControl is disposed:

eclipse.platform.ui/bundles/org.eclipse.jface.text/src/org/eclipse/jface/internal/text/html/BrowserInformationControl.java

Line 416 in 9e0cb2a

fBrowser= null;

Perhaps it is being disposed of somewhere in the lsp4e code but their ProgressListener is still active. I would say that it would be more fruitful to investigate on lsp4e first rather than platform.

[laeubi]

I would say that it would be more fruitful to investigate on lsp4e first rather than platform.

So you mean why fix it one better fix it on multiple places ;-)

In general I think it would be legal to throw an exception but

1. the API does not claim to throw any (an especially not a NPE)
2. looking at the code it looks like disposing might be time based in an async fashion so why not account for this