Fix partitioner leak and add null guard in

SourceViewer#computeStyleRanges()

Author: tobias-melcher

bundles/org.eclipse.jface.text/src/org/eclipse/jface/text/source/SourceViewer.java

@@ -1437,6 +1437,8 @@ private void uninstallTextViewer() {
 	 */
 	public List<StyleRange> computeStyleRanges(IDocument document, IRegion region) throws BadLocationException {
 		Assert.isTrue(Display.getCurrent() != null, "computeStyleRanges must be called from SWT UI thread"); //$NON-NLS-1$
+		IDocument originalDocument= getDocument();
+		Assert.isNotNull(originalDocument, "viewer must have a document before calling computeStyleRanges"); //$NON-NLS-1$
 		String partition= IDocumentExtension3.DEFAULT_PARTITIONING;
 		IPresentationReconciler reconciler= fPresentationReconciler;
 		if (reconciler instanceof IPresentationReconcilerExtension ext) {
@@ -1445,21 +1447,25 @@ public List<StyleRange> computeStyleRanges(IDocument document, IRegion region) t
 				partition= extPartition;
 			}
 		}
-		IDocument originalDocument= getDocument();
 		IDocumentPartitioner originalDocumentPartitioner= null;
-		if (document instanceof IDocumentExtension3
+		IDocumentExtension3 documentExt= null;
+		if (document instanceof IDocumentExtension3 docExt
 				&& originalDocument instanceof IDocumentExtension3 originalExt) {
+			documentExt= docExt;
 			originalDocumentPartitioner= originalExt.getDocumentPartitioner(partition);
 		}
+		IDocumentPartitioner externalDocPartitioner= null;
 		try {
-			if (originalDocumentPartitioner != null) {
+			if (originalDocumentPartitioner != null && documentExt != null) {
 				// Temporarily reconnect the partitioner to the external document so that
 				// presentation repairers compute highlighting against the right content.
-				// The finally block always restores it to the original document.
+				// The finally block always restores both documents to their original state.
+				externalDocPartitioner= documentExt.getDocumentPartitioner(partition);
 				originalDocumentPartitioner.disconnect();
 				originalDocumentPartitioner.connect(document);
-				((IDocumentExtension3) document).setDocumentPartitioner(partition, originalDocumentPartitioner);
+				documentExt.setDocumentPartitioner(partition, originalDocumentPartitioner);
 			} else {
+				externalDocPartitioner= document.getDocumentPartitioner();
 				document.setDocumentPartitioner(originalDocument.getDocumentPartitioner());
 			}
 			TextPresentation presentation= new TextPresentation(region, 1000);
@@ -1480,8 +1486,12 @@ public List<StyleRange> computeStyleRanges(IDocument document, IRegion region) t
 			}
 			return result;
 		} finally {
-			if (originalDocumentPartitioner != null) {
+			if (originalDocumentPartitioner != null && documentExt != null) {
+				originalDocumentPartitioner.disconnect();
 				originalDocumentPartitioner.connect(originalDocument);
+				documentExt.setDocumentPartitioner(partition, externalDocPartitioner);
+			} else {
+				document.setDocumentPartitioner(externalDocPartitioner);
 			}
 		}
 	}

tests/org.eclipse.jface.text.tests/src/org/eclipse/jface/text/tests/source/SourceViewerComputeStyleRangesTest.java

@@ -129,15 +129,20 @@ public void testOriginalDocumentNotAffected() throws Exception {
 		SourceViewer viewer= createConfiguredViewer();
 		String originalContent= "original content";
 		Document originalDoc= new Document(originalContent);
+		IDocumentPartitioner originalPartitioner= setupPartitioning(originalDoc);
+		assertNotNull(originalPartitioner);
 		viewer.setDocument(originalDoc);
-		IDocumentPartitioner originalPartitioner= originalDoc.getDocumentPartitioner();
 
 		Document externalDoc= new Document("some 'highlighted' text");
+		IDocumentPartitioner externalPartitioner= setupPartitioning(externalDoc);
+		assertNotNull(externalPartitioner);
 		viewer.computeStyleRanges(externalDoc, new Region(0, externalDoc.getLength()));
 
 		assertEquals(originalContent, originalDoc.get(), "Original document content must not change");
 		assertEquals(originalPartitioner, originalDoc.getDocumentPartitioner(),
 				"Original document partitioner must be restored");
+		assertEquals(externalPartitioner, externalDoc.getDocumentPartitioner(),
+				"External document partitioner must be restored");
 	}
 
 	@Test
@@ -193,6 +198,10 @@ public void testExceptionSafetyPartitionerRestored() throws Exception {
 
 		Document externalDoc= new Document("short");
 		setupNamedPartitioning(externalDoc);
+		IDocumentPartitioner externalPartitioner= externalDoc
+				.getDocumentPartitioner(NAMED_PARTITIONING);
+		assertNotNull(externalPartitioner, "External document should have a named partitioner");
+
 		try {
 			viewer.computeStyleRanges(externalDoc, new Region(0, 100));
 		} catch (BadLocationException expected) {
@@ -203,17 +212,25 @@ public void testExceptionSafetyPartitionerRestored() throws Exception {
 		IDocumentPartitioner restoredPartitioner= originalDoc
 				.getDocumentPartitioner(NAMED_PARTITIONING);
 		assertNotNull(restoredPartitioner, "Partitioner must be restored to original document after exception");
+		assertEquals(originalPartitioner, restoredPartitioner);
+
+		IDocumentPartitioner restoredExternalPartitioner= externalDoc
+				.getDocumentPartitioner(NAMED_PARTITIONING);
+		assertNotNull(restoredExternalPartitioner, "External partitioner must be restored to original document after exception");
+		assertEquals(externalPartitioner, restoredExternalPartitioner);
 	}
 
 	@Test
 	public void testNamedPartitioning() throws Exception {
 		SourceViewer viewer= createConfiguredViewerWithNamedPartitioning();
 		Document originalDoc= new Document("original 'content' here");
-		setupNamedPartitioning(originalDoc);
+		IDocumentPartitioner originalPartitioner= setupNamedPartitioning(originalDoc);
+		assertNotNull(originalPartitioner);
 		viewer.setDocument(originalDoc);
 
 		Document externalDoc= new Document("external 'styled' text");
-		setupNamedPartitioning(externalDoc);
+		IDocumentPartitioner externalPartitioner= setupNamedPartitioning(externalDoc);
+		assertNotNull(externalPartitioner);
 		List<StyleRange> styles= viewer.computeStyleRanges(externalDoc, new Region(0, externalDoc.getLength()));
 
 		assertNotNull(styles);
@@ -223,6 +240,12 @@ public void testNamedPartitioning() throws Exception {
 		IDocumentPartitioner restoredPartitioner= originalDoc
 				.getDocumentPartitioner(NAMED_PARTITIONING);
 		assertNotNull(restoredPartitioner, "Partitioner must be restored to original document");
+		assertEquals(originalPartitioner, restoredPartitioner);
+
+		IDocumentPartitioner restoredExternalPartitioner= externalDoc
+				.getDocumentPartitioner(NAMED_PARTITIONING);
+		assertNotNull(restoredExternalPartitioner, "External partitioner must be restored to external document");
+		assertEquals(externalPartitioner, restoredExternalPartitioner);
 	}
 
 	private SourceViewer createConfiguredViewer() {
@@ -266,10 +289,19 @@ private RuleBasedScanner createScanner() {
 		return scanner;
 	}
 
-	private void setupNamedPartitioning(Document document) {
+	private IDocumentPartitioner setupNamedPartitioning(Document document) {
 		IPartitionTokenScanner partitionScanner= new RuleBasedPartitionScanner();
 		IDocumentPartitioner partitioner= new FastPartitioner(partitionScanner, new String[] {});
 		document.setDocumentPartitioner(NAMED_PARTITIONING, partitioner);
 		partitioner.connect(document);
+		return partitioner;
+	}
+
+	private IDocumentPartitioner setupPartitioning(Document document) {
+		IPartitionTokenScanner partitionScanner= new RuleBasedPartitionScanner();
+		IDocumentPartitioner partitioner= new FastPartitioner(partitionScanner, new String[] {});
+		document.setDocumentPartitioner(partitioner);
+		partitioner.connect(document);
+		return partitioner;
 	}
 }