Keep leading and trailing blanks of template values visible in Excel (#295)

FillTemplate wrote inline strings without xml:space="preserve", so Excel
dropped leading and trailing blanks from filled values. Mark a <t> that
starts or ends with white space, or that still holds a list placeholder
whose value is filled in later, the way the exporter already does (#294).

Author: ybai08

src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.Impl.cs

@@ -54,6 +54,7 @@ private async Task GenerateSheetByUpdateModeAsync(ZipArchiveEntry sheetZipEntry,
         InjectSharedStrings(sharedStrings, rows);
         GetMergeCells(worksheet);
         UpdateDimensionAndGetRowsInfo(inputMaps, worksheet, rows, !mergeCells);
+        PreserveInlineStringSpaces(rows);
 
 #if NET
         var writer = XmlWriter.Create(stream, DocXmlWriterSettings);
@@ -90,6 +91,7 @@ private async Task GenerateSheetByCreateModeAsync(ZipArchiveEntry templateSheetZ
         InjectSharedStrings(sharedStrings, rows);
         GetMergeCells(worksheet);
         UpdateDimensionAndGetRowsInfo(inputMaps, worksheet, rows, !mergeCells);
+        PreserveInlineStringSpaces(rows);
 
 #if NET
         var writer = XmlWriter.Create(outputZipSheetEntryStream, DocXmlWriterSettings);
@@ -1068,6 +1070,23 @@ private static void InjectSharedStrings(IDictionary<int, string> sharedStrings,
         }
     }
 
+    // Excel drops leading and trailing blanks from a <t> without xml:space="preserve" (https://github.com/mini-software/MiniExcel/issues/295).
+    // Runs after the single values are filled in; a <t> still holding a placeholder gets its value later, so it is kept as well.
+    private static void PreserveInlineStringSpaces(IEnumerable<XElement> rows)
+    {
+        foreach (var row in rows)
+        {
+            foreach (var cell in row.Elements(SpreadsheetNs + "c"))
+            {
+                if (cell.Element(SpreadsheetNs + "is")?.Element(SpreadsheetNs + "t") is not { Value: { Length: > 0 } text } t)
+                    continue;
+
+                if (char.IsWhiteSpace(text[0]) || char.IsWhiteSpace(text[text.Length - 1]) || text.Contains("{{"))
+                    t.SetAttributeValue(XNamespace.Xml + "space", "preserve");
+            }
+        }
+    }
+
     private static void SetCellType(XElement cell, string type)
     {
         // Force inlineStr for strings

tests/MiniExcel.OpenXml.Tests/Issues/MiniExcelGiteeIssuesTests.cs

@@ -150,7 +150,7 @@ public void TestIssueI4DQUN()
         var sheetXml = SheetHelper.GetZipFileContent(path.ToString(), "xl/worksheets/sheet1.xml");
         // Template now uses inlineStr format (<is><t>...</t></is>) instead of SharedStrings (<v>...</v>)
         Assert.Contains("<t>Hello &amp; World &lt; , &gt; , \" , '</t>", sheetXml);
-        Assert.Contains("<t>Hello &amp; Value &lt; , &gt; , \" , '</t>", sheetXml);
+        Assert.Contains("<t xml:space=\"preserve\">Hello &amp; Value &lt; , &gt; , \" , '</t>", sheetXml);
     }
 
     [Fact]

tests/MiniExcel.OpenXml.Tests/Issues/MiniExcelGithubIssuesTests.cs

@@ -1,4 +1,5 @@
 using System.Text.RegularExpressions;
+using System.Xml.Linq;
 using MiniExcelLib.Core.Enums;
 using MiniExcelLib.Core.Exceptions;
 using MiniExcelLib.Core.Helpers;
@@ -1537,6 +1538,68 @@ public void TestIssue294()
         }
     }
 
+    /// Prefix and suffix blank space are hidden by Excel after FillTemplate - https://github.com/mini-software/MiniExcel/issues/295
+    [Fact]
+    public void TestIssue295()
+    {
+        static XElement GetInlineText(string sheetXml, string cellReference)
+        {
+            XNamespace ns = "http://schemas.openxmlformats.org/spreadsheetml/2006/main";
+            var cell = XDocument.Parse(sheetXml)
+                .Descendants(ns + "c")
+                .Single(c => c.Attribute("r")?.Value == cellReference);
+
+            return cell.Element(ns + "is")!.Element(ns + "t")!;
+        }
+
+        {
+            using var path = AutoDeletingPath.Create();
+            var templatePath = PathHelper.GetFile("xlsx/TestTemplateEasyFill.xlsx");
+            var value = new
+            {
+                Name = "  Jack",
+                CreateDate = new DateTime(2021, 01, 01),
+                VIP = true,
+                Points = 123
+            };
+            _excelTemplater.FillTemplate(path.ToString(), templatePath, value);
+
+            var sheetXml = SheetHelper.GetZipFileContent(path.ToString(), "xl/worksheets/sheet1.xml");
+            var a2 = GetInlineText(sheetXml, "A2");
+            Assert.Equal("  Jack", a2.Value);
+            Assert.Equal("preserve", a2.Attribute(XNamespace.Xml + "space")?.Value);
+
+            var e2 = GetInlineText(sheetXml, "E2");
+            Assert.Equal("  Jack has 123 points", e2.Value);
+            Assert.Equal("preserve", e2.Attribute(XNamespace.Xml + "space")?.Value);
+        }
+        {
+            using var path = AutoDeletingPath.Create();
+            var templatePath = PathHelper.GetFile("xlsx/TestTemplateBasicIEmumerableFill.xlsx");
+            var value = new
+            {
+                employees = new[]
+                {
+                    new { name = "  Jack", department = "HR  " },
+                    new { name = "Lisa", department = " IT " }
+                }
+            };
+            _excelTemplater.FillTemplate(path.ToString(), templatePath, value);
+
+            var sheetXml = SheetHelper.GetZipFileContent(path.ToString(), "xl/worksheets/sheet1.xml");
+            foreach (var (cellReference, expected) in new[] { ("A2", "  Jack"), ("B2", "HR  "), ("A3", "Lisa"), ("B3", " IT ") })
+            {
+                var t = GetInlineText(sheetXml, cellReference);
+                Assert.Equal(expected, t.Value);
+                Assert.Equal("preserve", t.Attribute(XNamespace.Xml + "space")?.Value);
+            }
+
+            var rows = _excelImporter.Query(path.ToString()).ToList();
+            Assert.Equal("  Jack", rows[1].A);
+            Assert.Equal(" IT ", rows[2].B);
+        }
+    }
+
     // SaveAs support Image type - https://github.com/mini-software/MiniExcel/issues/304
     [Fact]
     public void TestIssue304()