Move empty document range at EOF to start of removed range

Fixes #3380

Author: danthe1st

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

@@ -417,6 +417,9 @@ private void internalRemoveMasterDocumentRange(int offsetInMaster, int lengthInM
 			if (fragment.getOffset() == offsetInMaster) {
 				fragment.setOffset(offsetInMaster + lengthInMaster);
 				fragment.setLength(fragment.getLength() - lengthInMaster);
+				if (fragment.getLength() == 0 && offsetInMaster != 0 && offsetInMaster + lengthInMaster == getMasterDocument().getLength()) {
+					fragment.setOffset(offsetInMaster);
+				}
 			} else {
 				// split fragment into three fragments, let position updater remove it
 

tests/org.eclipse.text.tests/projection/org/eclipse/text/tests/ProjectionDocumentTest.java

@@ -27,6 +27,7 @@
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
+import org.junit.jupiter.api.Assertions;
 
 import org.eclipse.jface.text.BadLocationException;
 import org.eclipse.jface.text.DefaultLineTracker;
@@ -2652,4 +2653,39 @@ public void test29_38() {
 			assertTrue(false);
 		}
 	}
+
+	@Test
+	public void testFullDocumentRangeRemovedAtOnce() throws BadLocationException {
+		fSlaveDocument.addMasterDocumentRange(0, fMasterDocument.getLength());
+		fSlaveDocument.removeMasterDocumentRange(0, fMasterDocument.getLength());
+		Assertions.assertEquals("", fSlaveDocument.get());
+		Position[] fragments = fSlaveDocument.getFragments2();
+		Assertions.assertEquals(1, fragments.length);
+		Assertions.assertEquals(new Position(fMasterDocument.getLength(), 0), fragments[0]);
+	}
+
+	@Test
+	public void testFullDocumentRangeRemovedInTwoParts() throws BadLocationException {
+		fSlaveDocument.addMasterDocumentRange(0, fMasterDocument.getLength());
+		fSlaveDocument.removeMasterDocumentRange(0, 10);
+		Assertions.assertEquals(fMasterDocument.getLength() - 10, fSlaveDocument.getLength());
+		fSlaveDocument.removeMasterDocumentRange(10, fMasterDocument.getLength() - 10);
+		Assertions.assertEquals("", fSlaveDocument.get());
+		Position[] fragments = fSlaveDocument.getFragments2();
+		Assertions.assertEquals(1, fragments.length);
+		Assertions.assertEquals(new Position(10, 0), fragments[0]);
+	}
+
+	@Test
+	public void testRemovePartsOfDocument() throws BadLocationException {
+		fSlaveDocument.addMasterDocumentRange(0, fMasterDocument.getLength());
+		fSlaveDocument.removeMasterDocumentRange(0, 10);
+		Assertions.assertEquals(fMasterDocument.getLength() - 10, fSlaveDocument.getLength());
+		fSlaveDocument.removeMasterDocumentRange(10, fMasterDocument.getLength() - 20);
+		Assertions.assertEquals(fMasterDocument.get(fMasterDocument.getLength() - 10, 10),
+				fSlaveDocument.get());
+		Position[] fragments = fSlaveDocument.getFragments2();
+		Assertions.assertEquals(1, fragments.length);
+		Assertions.assertEquals(new Position(fMasterDocument.getLength() - 10, 10), fragments[0]);
+	}
 }