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Users of Geppetto have reported the NPE below. (The geppetto issue is at https://github.com/cloudsmith/geppetto/issues/238). Have asked for more information about if it is possible to recreate this problem. Also found that the same (or similar issues) have been reported here https://github.com/romainr/PigEditor/issues/7). Could it be a startup problem? java.lang.NullPointerException at org.eclipse.xtext.ui.editor.folding.DefaultFoldingStructureProvider.handleProjectionEnabled(DefaultFoldingStructureProvider.java:100) at org.eclipse.xtext.ui.editor.folding.DefaultFoldingStructureProvider$ProjectionChangeListener.projectionEnabled(DefaultFoldingStructureProvider.java:186) at org.eclipse.jface.text.source.projection.ProjectionViewer.fireProjectionEnabled(ProjectionViewer.java:489) at org.eclipse.jface.text.source.projection.ProjectionViewer.enableProjection(ProjectionViewer.java:537) at org.eclipse.jface.text.source.projection.ProjectionViewer.doOperation(ProjectionViewer.java:1441) at org.eclipse.xtext.ui.editor.XtextEditor.installFoldingSupport(XtextEditor.java:439) at org.eclipse.xtext.ui.editor.XtextEditor.createPartControl(XtextEditor.java:421) at org.eclipse.ui.internal.EditorReference.createPartHelper(EditorReference.java:670) at org.eclipse.ui.internal.EditorReference.createPart(EditorReference.java:465) at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:595) at org.eclipse.ui.internal.EditorReference.getEditor(EditorReference.java:289) at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditorBatched(WorkbenchPage.java:2945) at org.eclipse.ui.internal.WorkbenchPage.busyOpenEditor(WorkbenchPage.java:2850) at org.eclipse.ui.internal.WorkbenchPage.access$11(WorkbenchPage.java:2842) at org.eclipse.ui.internal.WorkbenchPage$10.run(WorkbenchPage.java:2793) at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70) at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2789) at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2773) at org.eclipse.ui.internal.WorkbenchPage.openEditor(WorkbenchPage.java:2756) at org.eclipse.ui.ide.IDE.openEditorOnFileStore(IDE.java:1155) at org.eclipse.ui.internal.ide.actions.OpenLocalFileAction.run(OpenLocalFileAction.java:107) at org.eclipse.ui.internal.ide.actions.OpenLocalFileAction.run(OpenLocalFileAction.java:76) at org.eclipse.ui.internal.PluginAction.runWithEvent(PluginAction.java:251) at org.eclipse.ui.internal.WWinPluginAction.runWithEvent(WWinPluginAction.java:229) at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584) at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:501) at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:411) at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84) at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4128) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1457) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1480) at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1465) at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1270) at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3974) at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3613) at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2696) at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2660) at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2494) at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:674) at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332) at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:667) at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149) at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:123) at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110) at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79) at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:344) at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:622) at org.eclipse.equinox.launcher.Main.basicRun(Main.java:577) at org.eclipse.equinox.launcher.Main.run(Main.java:1410)
Further investigation revealed that this was caused by using "open file" and opening a file that was not in the workspace. Rather than crashing, I would like to intervene and pop a dialog "opening files external to the workspace is not supported, please use linked files" (or some such). Where is a good place to do that?
The exception is from: protected void handleProjectionEnabled() { handleProjectionDisabled(); if (isInstalled()) { initialize(); editor.getDocument().addModelListener(this); // <--- NULL DOCUMENT } } where editor.getDocument() returns null, because XtextDocumentUtil.get(Object) receives a context for an XtextSourceViewer that returns null on getDocument(). Also See https://bugs.eclipse.org/bugs/show_bug.cgi?id=289212 (support opening external files). I do however just a way to *not open editor with NPE*.
I experimented, and protecting the DefaultFoldingStructureProvider.handleProjectionEnabled from the NPE, just moves the problem elsewhere. The next place is HighlightingReconciler.refresh:243 where editor.getDocument() is called without a check for null. If that is also fixed, the problem moves to StyledCellLabelProvider, where an assert is made like so: Assert.isTrue(this.viewer == null && this.column == null, "Label provider instance already in use"); Result is that editor opens up with an ugly "An error has occurred - see log for more details" with the message from the assert being logged. Trying to protect against the null document seems to be the wrong approach.
I'm facing a similar problem when trying to open a file outside the workspace (using an implementation of LanguageSpecificURIEditorOpener). The exceptions raised are those descriped in http://stackoverflow.com/questions/8239458/cannot-open-workspace-external-file-in-xtext-based-plugin.
fixed in 2.8.4 *** This bug has been marked as a duplicate of bug 470557 ***
