Restore original type from class file input in background

If ClassFileEditor is restored, underlined class file might be moved in
the meantime (e.g. library on classpath changed version so the type is
still there but the absolute class file path changed).

To check if the type is still on the classpath of the project might
freeze UI for some time, so move this check to a job.

If the job is running very early on startup, project classpath might be
not yet updated (see RequiredPluginsInitializer and UpdateClasspathsJob
in PDE which initialize classpath container lazily). In the case the
type is not found, listen to JDT model changes and refresh the input in
case the project classpath is updated.

Fixes #2245

Author: laeubi

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/ClassFileDocumentProvider.java

@@ -209,7 +209,7 @@ public ClassFileDocumentProvider() {
 	protected boolean setDocumentContent(IDocument document, IEditorInput editorInput, String encoding) throws CoreException {
 		if (editorInput instanceof IClassFileEditorInput) {
 			IClassFile classFile= ((IClassFileEditorInput) editorInput).getClassFile();
-			String source= classFile.getSource();
+			String source= getSourceIfPresent(classFile);
 			if (source == null)
 				source= ""; //$NON-NLS-1$
 			document.set(source);
@@ -218,6 +218,15 @@ protected boolean setDocumentContent(IDocument document, IEditorInput editorInpu
 		return super.setDocumentContent(document, editorInput, encoding);
 	}
 
+	private String getSourceIfPresent(IClassFile classFile) {
+		try {
+			return classFile.getSource();
+		} catch (JavaModelException e) {
+			//Assume no source...
+			return null;
+		}
+	}
+
 	/**
 	 * Creates an annotation model derived from the given class file editor input.
 	 *

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/ClassFileEditor.java

@@ -73,15 +73,18 @@
 import org.eclipse.ui.texteditor.ITextEditorActionConstants;
 
 import org.eclipse.jdt.core.ClasspathContainerInitializer;
+import org.eclipse.jdt.core.ElementChangedEvent;
 import org.eclipse.jdt.core.IClassFile;
 import org.eclipse.jdt.core.IClasspathAttribute;
 import org.eclipse.jdt.core.IClasspathContainer;
 import org.eclipse.jdt.core.IClasspathEntry;
+import org.eclipse.jdt.core.IElementChangedListener;
 import org.eclipse.jdt.core.IJavaElement;
 import org.eclipse.jdt.core.IJavaModelStatusConstants;
 import org.eclipse.jdt.core.IJavaProject;
 import org.eclipse.jdt.core.IOrdinaryClassFile;
 import org.eclipse.jdt.core.IPackageFragmentRoot;
+import org.eclipse.jdt.core.ISourceReference;
 import org.eclipse.jdt.core.IType;
 import org.eclipse.jdt.core.JavaCore;
 import org.eclipse.jdt.core.JavaModelException;
@@ -111,6 +114,75 @@
  * Java specific text editor.
  */
 public class ClassFileEditor extends JavaEditor implements ClassFileDocumentProvider.InputChangeListener {
+
+	private final class LoadJob extends Job implements IElementChangedListener {
+		private final IJavaElement fElement;
+		private volatile boolean continueListening;
+
+		private LoadJob(IJavaElement element) {
+			super("Restoring editor input for " + element.getElementName()); //$NON-NLS-1$
+			fElement= element;
+		}
+
+		@Override
+		protected IStatus run(IProgressMonitor monitor) {
+			try {
+				if(monitor.isCanceled() || disposed) {
+					continueListening = false;
+					return Status.CANCEL_STATUS;
+				}
+				if (!(fElement instanceof IOrdinaryClassFile) || fElement.exists()) {
+					return Status.OK_STATUS;
+				}
+				/*
+				 * Let's try to find the class file,
+				 * see https://bugs.eclipse.org/bugs/show_bug.cgi?id=83221
+				 */
+				IOrdinaryClassFile cf= (IOrdinaryClassFile)fElement;
+				IType type= cf.getType();
+				IJavaProject project= fElement.getJavaProject();
+				if (project != null) {
+					type= project.findType(type.getFullyQualifiedName());
+					if (type != null) {
+						continueListening = false;
+						IJavaElement javaElement= type.getParent();
+						IEditorInput editorInput= EditorUtility.getEditorInput(javaElement);
+						PlatformUI.getWorkbench().getDisplay().asyncExec(() -> {
+							if (!disposed) {
+								setInput(editorInput);
+								if(javaElement instanceof ISourceReference ref) {
+									setBreadcrumbInput(ref);
+								}
+							}
+						});
+					} else {
+						if (!continueListening) {
+							continueListening= true;
+							JavaCore.addElementChangedListener(this);
+						}
+					}
+				}
+			} catch (CoreException e) {
+				return e.getStatus();
+			} finally {
+				if (!continueListening) {
+					JavaCore.removeElementChangedListener(this);
+				}
+			}
+			return Status.OK_STATUS;
+		}
+
+		@Override
+		public boolean belongsTo(Object family) {
+			return family == ClassFileEditor.class;
+		}
+
+		@Override
+		public void elementChanged(ElementChangedEvent event) {
+			schedule(100);
+		}
+	}
+
 	/**
 	 * A form to attach source to a class file.
 	 */
@@ -409,7 +481,9 @@ private void updateCodeView(StyledText styledText, IClassFile classFile) {
 			try {
 				content= disassembler.disassemble(classFile.getBytes(), "\n", ClassFileBytesDisassembler.DETAILED); //$NON-NLS-1$
 			} catch (JavaModelException ex) {
-				JavaPlugin.log(ex.getStatus());
+				if (!ex.isDoesNotExist()) {
+					JavaPlugin.log(ex.getStatus());
+				}
 			} catch (ClassFormatException ex) {
 				JavaPlugin.log(ex);
 			}
@@ -511,6 +585,7 @@ private boolean isEqualInput(IEditorInput input1, IEditorInput input2) {
 	 * @since 3.3
 	 */
 	private StyledText fNoSourceTextWidget;
+	private volatile boolean disposed;
 
 	/**
 	 * Default constructor.
@@ -644,21 +719,8 @@ public boolean isEditorInputReadOnly() {
 	protected IEditorInput transformEditorInput(IEditorInput input) throws CoreException{
 		if (input instanceof HandleEditorInput handle) {
 			IJavaElement element= handle.getElement();
-			if (!element.exists() && element instanceof IOrdinaryClassFile) {
-				/*
-				 * Let's try to find the class file,
-				 * see https://bugs.eclipse.org/bugs/show_bug.cgi?id=83221
-				 */
-				IOrdinaryClassFile cf= (IOrdinaryClassFile)element;
-				IType type= cf.getType();
-				IJavaProject project= element.getJavaProject();
-				if (project != null) {
-					type= project.findType(type.getFullyQualifiedName());
-					if (type == null)
-						return null;
-					element= type.getParent();
-				}
-			}
+			LoadJob job= new LoadJob(element);
+			job.schedule();
 			input= EditorUtility.getEditorInput(element);
 		}
 		if (input instanceof IFileEditorInput) {
@@ -694,21 +756,6 @@ private void doSetInputCached(IEditorInput input) throws CoreException {
 					message,
 					null));
 		}
-
-		JavaModelException e= probeInputForSource(input);
-		if (e != null) {
-			IClassFileEditorInput classFileEditorInput= (IClassFileEditorInput) input;
-			IClassFile file= classFileEditorInput.getClassFile();
-			IJavaProject javaProject= file.getJavaProject();
-			if (!javaProject.exists() || !javaProject.isOnClasspath(file)) {
-				throw new CoreException(JavaUIStatus.createError(
-						IJavaModelStatusConstants.INVALID_RESOURCE,
-						JavaEditorMessages.ClassFileEditor_error_classfile_not_on_classpath,
-						null));
-			}
-			throw e;
-		}
-
 		IDocumentProvider documentProvider= getDocumentProvider();
 		if (documentProvider instanceof ClassFileDocumentProvider) {
 			((ClassFileDocumentProvider) documentProvider).removeInputChangeListener(this);
@@ -799,23 +846,6 @@ private void createPartControlCached(Composite parent) {
 		}
 	}
 
-	private JavaModelException probeInputForSource(IEditorInput input) {
-		if (input == null) {
-			return null;
-		}
-
-		IClassFileEditorInput classFileEditorInput= (IClassFileEditorInput) input;
-		IClassFile file= classFileEditorInput.getClassFile();
-
-		try {
-			file.getSourceRange();
-		} catch (JavaModelException e) {
-			return e;
-		}
-
-		return null;
-	}
-
 	/**
 	 * Checks if the class file input has no source attached. If so, a source attachment form is shown.
 	 *
@@ -836,7 +866,7 @@ private void verifyInput(IEditorInput input) throws JavaModelException {
 		boolean wasUsingSourceCopyAction= fSourceCopyAction == getAction(ITextEditorActionConstants.COPY);
 
 		// show source attachment form if no source found
-		if (file.getSourceRange() == null) {
+		if (!hasSource(file)) {
 			// dispose old source attachment form
 			if (fSourceAttachmentForm != null) {
 				fSourceAttachmentForm.dispose();
@@ -925,6 +955,15 @@ public void run() {
 		}
 	}
 
+	private static boolean hasSource(IClassFile file) {
+		try {
+			return file.getSourceRange() != null;
+		} catch (JavaModelException e) {
+			//assume no source then...
+			return false;
+		}
+	}
+
 	/*
 	 * @see ClassFileDocumentProvider.InputChangeListener#inputChanged(IClassFileEditorInput)
 	 */
@@ -973,6 +1012,7 @@ public void doOperation(int operation) {
 	 */
 	@Override
 	public void dispose() {
+		disposed = true;
 		// http://bugs.eclipse.org/bugs/show_bug.cgi?id=18510
 		IDocumentProvider documentProvider= getDocumentProvider();
 		if (documentProvider instanceof ClassFileDocumentProvider) {

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/InternalClassFileEditorInput.java

@@ -18,7 +18,6 @@
 import java.io.IOException;
 import java.nio.file.Files;
 
-import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IPath;
 import org.eclipse.core.runtime.Path;
 
@@ -45,7 +44,7 @@ public class InternalClassFileEditorInput implements IClassFileEditorInput, IPer
 
 	private IClassFile fClassFile;
 
-	private IPath fPath;
+	private volatile IPath fPath;
 
 	public InternalClassFileEditorInput(IClassFile classFile) {
 		fClassFile= classFile;
@@ -182,10 +181,12 @@ private static IPath writeToTempFile(IClassFile classFile) {
 			return new Path(file.toString());
 		} catch (IOException e) {
 			JavaPlugin.log(e);
-		} catch (CoreException e) {
-			JavaPlugin.log(e.getStatus());
+		} catch (JavaModelException ex) {
+			if (!ex.isDoesNotExist()) {
+				JavaPlugin.log(ex.getStatus());
+			}
 		}
-		throw new IllegalArgumentException("Could not create temporary file."); //$NON-NLS-1$
+		return IPath.EMPTY;
 	}
 
 }

org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java

@@ -1999,9 +1999,8 @@ private void hideBreadcrumb() {
 	/**
 	 * Sets the breadcrumb input to the given element.
 	 * @param element the element to use as input for the breadcrumb
-	 * @since 3.4
 	 */
-	private void setBreadcrumbInput(ISourceReference element) {
+	protected void setBreadcrumbInput(ISourceReference element) {
 		if (fBreadcrumb == null)
 			return;