spreadsheet: add method to clear cached formula results

spreadsheet/sheet.go

@@ -505,3 +505,17 @@ func (s Sheet) AddDataValidation() DataValidation {
 	s.x.DataValidations.CountAttr = gooxml.Uint32(uint32(len(s.x.DataValidations.DataValidation)))
 	return DataValidation{dv}
 }
+
+// ClearCachedFormulaResults clears any computed formula values that are stored
+// in the sheet. This may be required if you modify cells that are used as a
+// formula input to force the formulas to be recomputed the next time the sheet
+// is opened in Excel.
+func (s *Sheet) ClearCachedFormulaResults() {
+	for _, r := range s.Rows() {
+		for _, c := range r.Cells() {
+			if c.X().F != nil {
+				c.X().V = nil
+			}
+		}
+	}
+}

spreadsheet/sheet_test.go

@@ -11,6 +11,7 @@ import (
 	"math/rand"
 	"testing"
 
+	"baliance.com/gooxml"
 	"baliance.com/gooxml/spreadsheet"
 )
 
@@ -186,3 +187,16 @@ func TestSheetExtents(t *testing.T) {
 	}
 
 }
+
+func TestSheetClearCachedFormula(t *testing.T) {
+	ss := spreadsheet.New()
+	sheet := ss.AddSheet()
+	cell := sheet.Cell("A1")
+	cell.SetFormulaRaw("foo")
+	cell.X().V = gooxml.String("cached-results")
+	sheet.ClearCachedFormulaResults()
+	if cell.X().V != nil {
+		t.Errorf("cached result not cleared")
+	}
+
+}

spreadsheet/workbook.go

@@ -414,3 +414,13 @@ func (wb *Workbook) DefinedNames() []DefinedName {
 	}
 	return ret
 }
+
+// ClearCachedFormulaResults clears any computed formula values that are stored
+// in the sheet. This may be required if you modify cells that are used as a
+// formula input to force the formulas to be recomputed the next time the sheet
+// is opened in Excel.
+func (wb *Workbook) ClearCachedFormulaResults() {
+	for _, s := range wb.Sheets() {
+		s.ClearCachedFormulaResults()
+	}
+}