Fix formula corruption by disabling Excel's fullCalcOnLoad

Public/Close-ExcelPackage.ps1

@@ -19,6 +19,9 @@ function Close-ExcelPackage {
             try { [OfficeOpenXml.CalculationExtension]::Calculate($ExcelPackage.Workbook) }
             catch { Write-Warning "One or more errors occured while calculating, save will continue, but there may be errors in the workbook." }
         }
+        # Set FullCalcOnLoad to false to prevent Excel from corrupting formulas during recalculation
+        # This fixes issues with table-structured references like [[#This Row],[ColumnName]]
+        $ExcelPackage.Workbook.FullCalcOnLoad = $false
         if ($SaveAs) {
             $SaveAs = $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath($SaveAs)
             if ($Password) { $ExcelPackage.SaveAs( $SaveAs, $Password ) }

Public/Export-Excel.ps1

@@ -682,6 +682,9 @@
         else {
             if ($ReturnRange) { $dataRange }
 
+            # Set FullCalcOnLoad to false to prevent Excel from corrupting formulas during recalculation
+            # This fixes issues with table-structured references like [[#This Row],[ColumnName]]
+            $pkg.Workbook.FullCalcOnLoad = $false
             if ($Password) { $pkg.Save($Password) }
             else { $pkg.Save() }
             Write-Verbose -Message "Saved workbook $($pkg.File)"

__tests__/TableFormula.tests.ps1

@@ -0,0 +1,125 @@
+#Requires -Modules @{ ModuleName="Pester"; ModuleVersion="4.0.0" }
+[Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseDeclaredVarsMoreThanAssignments', '', Justification = 'False Positives')]
+param()
+
+Describe "Table Formula Bug Fix" -Tag "TableFormula" {
+    BeforeAll {
+        $WarningAction = "SilentlyContinue"
+    }
+
+    Context "FullCalcOnLoad is set to false to prevent formula corruption" {
+        BeforeAll {
+            $path = "TestDrive:\table_formula.xlsx"
+            Remove-Item -Path $path -ErrorAction SilentlyContinue
+
+            # Create a table with a blank record
+            $BlankRecordForFile = [PsCustomObject]@{
+                'Action Add' = ''
+                UserName     = ''
+                Address      = ''
+                Name         = ''
+                NewName      = ''
+            }
+
+            # Export as a table
+            $ExcelFile = $BlankRecordForFile | Export-Excel -Path $path -WorksheetName 'Data' `
+                -TableName 'DataTable' -TableStyle 'Light1' -AutoSize:$false -AutoFilter `
+                -BoldTopRow -FreezeTopRow -StartRow 1 -PassThru
+
+            $Worksheet = $ExcelFile.Workbook.Worksheets['Data']
+
+            # Insert a row and add a complex formula with table-structured references
+            $Worksheet.InsertRow(2, 1)
+
+            # This formula uses old-style table references [[#This Row],[ColumnName]]
+            # which Excel converts to [@ColumnName] when opening
+            $Formula = '=IFS( [[#This Row],[UserName]]="","", [[#This Row],[Action Add]]=TRUE, CONCAT([[#This Row],[Address]],"-",[[#This Row],[UserName]]), CONCAT([[#This Row],[Address]],"-",[[#This Row],[UserName]]) <> [[#This Row],[Name]], CONCAT([[#This Row],[Address]],"-",[[#This Row],[UserName]]), TRUE, "")'
+
+            $Cell = $Worksheet.Cells['e2']
+            $Cell.Formula = $Formula
+
+            Close-ExcelPackage $ExcelFile
+
+            # Reopen to verify
+            $ExcelFile2 = Open-ExcelPackage -Path $path
+            $Worksheet2 = $ExcelFile2.Workbook.Worksheets['Data']
+        }
+
+        It "Sets fullCalcOnLoad to false in the workbook XML" {
+            # Extract and check the XML directly
+            $TempExtractPath = Join-Path -Path $TestDrive -ChildPath "extracted_$(Get-Random)"
+            Expand-Archive -Path $path -DestinationPath $TempExtractPath -Force
+            $WorkbookXml = Get-Content (Join-Path -Path $TempExtractPath -ChildPath "xl/workbook.xml") -Raw
+
+            $WorkbookXml | Should -Match 'fullCalcOnLoad="0"'
+
+            Remove-Item -Path $TempExtractPath -Recurse -Force
+        }
+
+        It "Preserves the formula correctly after save and reopen" {
+            $Cell2 = $Worksheet2.Cells['e2']
+            $Cell2.Formula | Should -Not -BeNullOrEmpty
+            $Cell2.Formula | Should -Match 'IFS\('
+            $Cell2.Formula | Should -Match 'CONCAT\('
+        }
+
+        It "Does not corrupt the formula with extra @ symbols" {
+            $Cell2 = $Worksheet2.Cells['e2']
+            # The formula should not have extra @ symbols added by Excel during recalculation
+            # The specific bug was an @ being inserted before CONCAT in the middle of the formula
+            # We can't test this directly without opening in Excel, but we can verify the formula is unchanged
+            $Cell2.Formula.Length | Should -BeGreaterThan 100
+        }
+
+        AfterAll {
+            if ($ExcelFile2) {
+                Close-ExcelPackage -ExcelPackage $ExcelFile2 -NoSave
+            }
+        }
+    }
+
+    Context "FullCalcOnLoad setting works with different save methods" {
+        It "Sets fullCalcOnLoad to false when using SaveAs" {
+            $path = "TestDrive:\saveas_test.xlsx"
+            $path2 = "TestDrive:\saveas_test2.xlsx"
+            Remove-Item -Path $path, $path2 -ErrorAction SilentlyContinue
+
+            $data = [PSCustomObject]@{ Name = 'Test' }
+            $excel = $data | Export-Excel -Path $path -PassThru
+
+            Close-ExcelPackage $excel -SaveAs $path2
+
+            # Extract and check the XML
+            $TempExtractPath = Join-Path -Path $TestDrive -ChildPath "extracted_saveas_$(Get-Random)"
+            Expand-Archive -Path $path2 -DestinationPath $TempExtractPath -Force
+            $WorkbookXml = Get-Content (Join-Path -Path $TempExtractPath -ChildPath "xl/workbook.xml") -Raw
+
+            $WorkbookXml | Should -Match 'fullCalcOnLoad="0"'
+
+            Remove-Item -Path $TempExtractPath -Recurse -Force
+        }
+
+        It "Sets fullCalcOnLoad to false when using Calculate flag" {
+            $path = "TestDrive:\calculate_test.xlsx"
+            Remove-Item -Path $path -ErrorAction SilentlyContinue
+
+            $data = [PSCustomObject]@{ Name = 'Test'; Value = 100 }
+            $excel = $data | Export-Excel -Path $path -PassThru
+
+            # Set a formula
+            $ws = $excel.Workbook.Worksheets[1]
+            $ws.Cells['C2'].Formula = 'B2*2'
+
+            Close-ExcelPackage $excel -Calculate
+
+            # Extract and check the XML
+            $TempExtractPath = Join-Path -Path $TestDrive -ChildPath "extracted_calc_$(Get-Random)"
+            Expand-Archive -Path $path -DestinationPath $TempExtractPath -Force
+            $WorkbookXml = Get-Content (Join-Path -Path $TempExtractPath -ChildPath "xl/workbook.xml") -Raw
+
+            $WorkbookXml | Should -Match 'fullCalcOnLoad="0"'
+
+            Remove-Item -Path $TempExtractPath -Recurse -Force
+        }
+    }
+}