From 08207ea11033449739e500cc6d3356d105529b4d Mon Sep 17 00:00:00 2001
From: xuri <xuri.me@gmail.com>
Date: Mon, 2 Oct 2023 00:06:38 +0800
Subject: [PATCH] This closes #1677, fix the incorrect custom number format ID
 allocated

- Improve compatibility with empty custom number format code
---
 styles.go    | 22 ++++++++++------------
 xmlStyles.go |  2 +-
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/styles.go b/styles.go
index 1de83bcb03..40505b7b9e 100644
--- a/styles.go
+++ b/styles.go
@@ -1694,20 +1694,18 @@ func newNumFmt(styleSheet *xlsxStyleSheet, style *Style) int {
 
 // setCustomNumFmt provides a function to set custom number format code.
 func setCustomNumFmt(styleSheet *xlsxStyleSheet, style *Style) int {
-	nf := xlsxNumFmt{FormatCode: *style.CustomNumFmt}
-
-	if styleSheet.NumFmts != nil {
-		nf.NumFmtID = styleSheet.NumFmts.NumFmt[len(styleSheet.NumFmts.NumFmt)-1].NumFmtID + 1
-		styleSheet.NumFmts.NumFmt = append(styleSheet.NumFmts.NumFmt, &nf)
-		styleSheet.NumFmts.Count++
-	} else {
-		nf.NumFmtID = 164
-		numFmts := xlsxNumFmts{
-			NumFmt: []*xlsxNumFmt{&nf},
-			Count:  1,
+	nf := xlsxNumFmt{NumFmtID: 163, FormatCode: *style.CustomNumFmt}
+	if styleSheet.NumFmts == nil {
+		styleSheet.NumFmts = &xlsxNumFmts{}
+	}
+	for _, numFmt := range styleSheet.NumFmts.NumFmt {
+		if numFmt != nil && nf.NumFmtID < numFmt.NumFmtID {
+			nf.NumFmtID = numFmt.NumFmtID
 		}
-		styleSheet.NumFmts = &numFmts
 	}
+	nf.NumFmtID++
+	styleSheet.NumFmts.NumFmt = append(styleSheet.NumFmts.NumFmt, &nf)
+	styleSheet.NumFmts.Count = len(styleSheet.NumFmts.NumFmt)
 	return nf.NumFmtID
 }
 
diff --git a/xmlStyles.go b/xmlStyles.go
index 3dd61c3307..613001c8e4 100644
--- a/xmlStyles.go
+++ b/xmlStyles.go
@@ -296,7 +296,7 @@ type xlsxNumFmts struct {
 // of a cell.
 type xlsxNumFmt struct {
 	NumFmtID     int    `xml:"numFmtId,attr"`
-	FormatCode   string `xml:"formatCode,attr,omitempty"`
+	FormatCode   string `xml:"formatCode,attr"`
 	FormatCode16 string `xml:"http://schemas.microsoft.com/office/spreadsheetml/2015/02/main formatCode16,attr,omitempty"`
 }