This closes #2254, fixx duplicate style creation when using default font or fill (#2255)

Author: susautw

styles.go

@@ -1115,13 +1115,13 @@ var (
 			return xf.NumFmtID != nil && *xf.NumFmtID == numFmtID
 		},
 		"font": func(fontID int, xf xlsxXf, style *Style) bool {
-			if style.Font == nil {
+			if style.Font == nil || fontID == 0 {
 				return (xf.FontID == nil || *xf.FontID == 0) && (xf.ApplyFont == nil || !*xf.ApplyFont)
 			}
 			return xf.FontID != nil && *xf.FontID == fontID && xf.ApplyFont != nil && *xf.ApplyFont
 		},
 		"fill": func(fillID int, xf xlsxXf, style *Style) bool {
-			if style.Fill.Type == "" {
+			if style.Fill.Type == "" || fillID == 0 {
 				return (xf.FillID == nil || *xf.FillID == 0) && (xf.ApplyFill == nil || !*xf.ApplyFill)
 			}
 			return xf.FillID != nil && *xf.FillID == fillID && xf.ApplyFill != nil && *xf.ApplyFill

styles_test.go

@@ -544,6 +544,15 @@ func TestNewStyle(t *testing.T) {
 		assert.NoError(t, f.SetCellStyle("Sheet1", "A1", "A1", styleID))
 		assert.NoError(t, f.SaveAs(filepath.Join("test", "TestSetFontCharset.xlsx")))
 	})
+
+	t.Run("recreate_default_style", func(t *testing.T) {
+		f := NewFile()
+		style2, err := f.GetStyle(0) // Get the default style
+		assert.NoError(t, err)
+		styleId, err := f.NewStyle(style2) // Try to recreate the same style. Should return style ID 0
+		assert.NoError(t, err)
+		assert.Equal(t, 0, styleId)
+	})
 }
 
 func TestConditionalStyle(t *testing.T) {