Prevent IllegalStateException setting visible region with collapsed

projection region

Author: danthe1st

bundles/org.eclipse.text/projection/org/eclipse/jface/text/projection/ProjectionDocument.java

@@ -15,6 +15,8 @@
 package org.eclipse.jface.text.projection;
 
 import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
 import java.util.List;
 
 import org.eclipse.jface.text.AbstractDocument;
@@ -438,6 +440,11 @@ private void internalRemoveMasterDocumentRange(int offsetInMaster, int lengthInM
 				segment= new Segment(offset, fragment.segment.getOffset() + fragment.segment.getLength() - offset);
 				newFragment.segment= segment;
 				segment.fragment= newFragment;
+				if (newFragment.getLength() != 0 && fMasterDocument.containsPosition(fFragmentsCategory, newFragment.getOffset(), 0)) {
+					// prevent inserting position with non-zero length after position with 0-length by removing zero-length position
+					removePositionAt(fMasterDocument, fFragmentsCategory, new Position(newFragment.getOffset(), 0));
+					removePositionAt(this, fSegmentsCategory, new Position(fMapping.toImageOffset(newFragment.getOffset()), 0));
+				}
 				fMasterDocument.addPosition(fFragmentsCategory, newFragment);
 				addPosition(fSegmentsCategory, segment);
 
@@ -454,6 +461,14 @@ private void internalRemoveMasterDocumentRange(int offsetInMaster, int lengthInM
 		}
 	}
 
+	private void removePositionAt(IDocument document, String category, Position toRemove) throws BadPositionCategoryException {
+		Position[] positions= document.getPositions(category);
+		int index= Arrays.binarySearch(positions, toRemove, Comparator.comparingInt(Position::getOffset));
+		if (index != -1) {
+			document.removePosition(category, positions[index]);
+		}
+	}
+
 	/**
 	 * Returns the sequence of all master document regions which are contained
 	 * in the given master document range and which are not yet part of this

tests/org.eclipse.jface.text.tests/src/org/eclipse/jface/text/tests/ProjectionViewerTest.java

@@ -28,11 +28,13 @@
 import org.eclipse.jface.text.BadLocationException;
 import org.eclipse.jface.text.Document;
 import org.eclipse.jface.text.IDocument;
+import org.eclipse.jface.text.IDocumentInformationMapping;
 import org.eclipse.jface.text.IRegion;
 import org.eclipse.jface.text.ITextOperationTarget;
 import org.eclipse.jface.text.ITextSelection;
 import org.eclipse.jface.text.Position;
 import org.eclipse.jface.text.Region;
+import org.eclipse.jface.text.projection.ProjectionDocument;
 import org.eclipse.jface.text.source.AnnotationModel;
 import org.eclipse.jface.text.source.IOverviewRuler;
 import org.eclipse.jface.text.source.IVerticalRuler;
@@ -433,6 +435,72 @@ public void testSetVisibleRegionExpandsBorderingProjectionRegions() {
 		}
 	}
 
+	@Test
+	public void testImageLineStateAfterSettingVisibleRegionsWithProjections() throws BadLocationException {
+		// https://github.com/eclipse-platform/eclipse.platform.ui/pull/3456
+		Shell shell= new Shell();
+		shell.setLayout(new FillLayout());
+		TestProjectionViewer viewer= new TestProjectionViewer(shell, null, null, false, SWT.NONE);
+		String documentContent= """
+				public class TM {
+					void a() {
+						// ...
+					}
+
+					void b() {
+						// ...
+					}
+
+					void c() {
+						// ...
+					}
+				}
+				""";
+		Document document= new Document(documentContent);
+		viewer.setDocument(document, new AnnotationModel());
+		viewer.enableProjection();
+		addAnnotationBetween(viewer, new ProjectionAnnotation(false), "\tvoid a()", "\t}");
+		ProjectionAnnotation annotationToCollapse= new ProjectionAnnotation(false);
+		addAnnotationBetween(viewer, annotationToCollapse, "\tvoid b()", "\t}");
+		addAnnotationBetween(viewer, new ProjectionAnnotation(false), "\tvoid c()", "\t}");
+
+		shell.setVisible(true);
+		try {
+			viewer.getProjectionAnnotationModel().collapse(annotationToCollapse);
+
+			Position firstMethod= findPositionFromStartAndEndText(viewer, "\tvoid a()", "}");
+			viewer.setVisibleRegion(firstMethod.getOffset(), firstMethod.getLength() + 1);
+			viewer.setVisibleRegion(documentContent.indexOf("class"), documentContent.length() - documentContent.indexOf("class"));
+
+			IDocumentInformationMapping mapping= ((ProjectionDocument) viewer.getVisibleDocument()).getDocumentInformationMapping();
+			// toImageLine should not throw exceptions
+			for (int i= 0; i < 5; i++) {
+				int imageLine= mapping.toImageLine(i);// should not throw exception
+				assertEquals(i, imageLine);
+			}
+			assertEquals(-1, mapping.toImageLine(6), "should still be collapsed");
+			for (int i= 7; i < documentContent.split("\n").length; i++) {
+				int imageLine= mapping.toImageLine(i);// should not throw exception
+				assertEquals(i - 1, imageLine);
+			}
+		} finally {
+			shell.dispose();
+		}
+	}
+
+	private void addAnnotationBetween(TestProjectionViewer viewer, ProjectionAnnotation annotationToCollapse, String startText, String endText) {
+		Position position= findPositionFromStartAndEndText(viewer, startText, endText);
+		viewer.getProjectionAnnotationModel().addAnnotation(annotationToCollapse, position);
+	}
+
+	private Position findPositionFromStartAndEndText(TestProjectionViewer viewer, String startText, String endText) {
+		String documentContent= viewer.getDocument().get();
+		int startIndex= documentContent.indexOf(startText);
+		int endIndex= documentContent.indexOf(endText, startIndex + 1);
+		Position position= new Position(startIndex, endIndex - startIndex);
+		return position;
+	}
+
 	@Test
 	public void testProjectionRegionsShownOnlyInVisibleRegion() {
 		Shell shell= new Shell(Display.getCurrent());