Bounds check delete regions in rope buffer

ui/buffer/rope.go

@@ -114,7 +114,17 @@ func (b *RopeBuffer) Insert(line, col int, value []byte) {
 // Remove deletes any characters between startLine, startCol, and endLine,
 // endCol, inclusive bounds.
 func (b *RopeBuffer) Remove(startLine, startCol, endLine, endCol int) {
-	(*rope.Node)(b).Remove(b.pos(startLine, startCol), b.pos(endLine, endCol)+1)
+	start := b.pos(startLine, startCol)
+	end := b.pos(endLine, endCol) + 1
+
+	if len := (*rope.Node)(b).Len(); end >= len {
+		end = len
+		if start > end {
+			start = end
+		}
+	}
+
+	(*rope.Node)(b).Remove(start, end)
 }
 
 // Returns the number of occurrences of 'sequence' in the buffer, within the range

ui/buffer/rope_test.go

@@ -4,16 +4,29 @@ import "testing"
 
 func TestRopeInserting(t *testing.T) {
 	var buf Buffer = NewRopeBuffer([]byte("some"))
-	buf.Insert(0, 4, []byte(" text")) // Insert " text" after "some"
+	buf.Insert(0, 4, []byte(" text\n")) // Insert " text" after "some"
 	buf.Insert(0, 0, []byte("with\n\t"))
-	// "with\n\tsome text"
+	//with
+	//	some text
+	//
 
 	buf.Remove(0, 4, 1, 5) // Delete from line 0, col 4, to line 1, col 6 "\n\tsome "
 
-	if str := string(buf.Bytes()); str != "withtext" {
+	if str := string(buf.Bytes()); str != "withtext\n" {
 		t.Errorf("string does not match \"withtext\", got %#v", str)
 		t.Fail()
 	}
+
+	//withtext
+	//
+
+	// Note the inclusive bounds and pointing to last line, first column.
+	buf.Remove(0, 0, 1, 0) // Delete all of the buffer
+
+	if str := string(buf.Bytes()); str != "" {
+		t.Errorf("string does not math \"\", got %#v", str)
+		t.Fail()
+	}
 }
 
 func TestRopeBounds(t *testing.T) {