Forcibly remove a range representing a table if its data source is empty (#251) (#323)

Author: Pankraty

ClosedXML.Report/RangeInterpreter.cs

@@ -177,6 +177,20 @@ string EvalString(string str)
                 {
                     var growedRange = rng.GrowToMergedRanges();
                     var items = nr.RangeData as object[] ?? nr.RangeData.Cast<object>().ToArray();
+                    if (!items.Any())
+                    {
+                        if (growedRange.IsOptionsRowEmpty())
+                        {
+                            growedRange.Delete(XLShiftDeletedCells.ShiftCellsUp);
+                        }
+                        else
+                        {
+                            var rangeWithoutOptionsRow = growedRange.Worksheet
+                                .Range(growedRange.FirstCell(), growedRange.LastCell().CellAbove());
+                            rangeWithoutOptionsRow.Delete(XLShiftDeletedCells.ShiftCellsUp);
+                        }
+                        continue;
+                    }
                     var tplt = RangeTemplate.Parse(nr.NamedRange.Name, growedRange, _errors, _variables);
                     using (var buff = tplt.Generate(items))
                     {

tests/ClosedXML.Report.Tests/RangeInterpreterTests.cs

@@ -104,6 +104,37 @@ public void ShouldNotThrowExceptionIfAccessSomeChildrenNullProp()
             ws.Cell("B4").GetString().Should().Be("Material 1");
         }
 
+        [Fact]
+        public void ShouldDestroyEmptyTable()
+        {
+            //See #251
+            var template = CreateOrderTemplate();
+            var ws = template.Workbook.Worksheets.First();
+
+            ws.Cell("B4").SetValue("This list is empty");
+            ws.Cell("B5").SetValue("{{item.Name}}");
+            ws.Range("A5:B6").AddToNamed("Empty");
+
+            ws.Cell("B7").SetValue("This list is populated");
+            ws.Cell("B8").SetValue("{{item.Name}}");
+            ws.Range("A8:B9").AddToNamed("Populated");
+
+            var model = new
+            {
+                Empty = new List<Item>(),
+                Populated = new[]
+                {
+                    new Item("It works", null)
+                }
+            };
+            template.AddVariable(model);
+            template.Generate();
+
+            ws.Cell("B4").GetString().Should().Be("This list is empty");
+            ws.Cell("B5").GetString().Should().Be("This list is populated");
+            ws.Cell("B6").GetString().Should().Be("It works");
+        }
+
         private XLTemplate CreateOrderTemplate()
         {
             var wbTemplate = new XLWorkbook();

tests/ClosedXML.Report.Tests/TempSheetBufferTests.cs

@@ -41,8 +41,8 @@ public void CanRenderRangeForEmptySet()
                 template.AddVariable("List", new List<string>());
                 template.Generate();
 
-                ws.Cell("B3").GetString().Should().Be("Cell below");
-                ws.Cell("B4").GetString().Should().Be("");
+                ws.Cell("B2").GetString().Should().Be("Cell below");
+                ws.Cell("B3").GetString().Should().Be("");
             }
         }