improvement compatibility for the XML ignorable namespace

lib.go

@@ -379,14 +379,14 @@ func (f *File) replaceNameSpaceBytes(path string, contentMarshal []byte) []byte
 func (f *File) addNameSpaces(path string, ns xml.Attr) {
 	exist := false
 	mc := false
-	ignore := false
+	ignore := -1
 	if attr, ok := f.xmlAttr[path]; ok {
-		for _, attribute := range attr {
+		for i, attribute := range attr {
 			if attribute.Name.Local == ns.Name.Local && attribute.Name.Space == ns.Name.Space {
 				exist = true
 			}
-			if attribute.Name.Local == "Ignorable" && attribute.Name.Space == "mc" {
+			if attribute.Name.Local == "Ignorable" && getXMLNamespace(attribute.Name.Space, attr) == "mc" {
-				ignore = true
+				ignore = i
 			}
 			if attribute.Name.Local == "mc" && attribute.Name.Space == "xmlns" {
 				mc = true
@@ -398,12 +398,23 @@ func (f *File) addNameSpaces(path string, ns xml.Attr) {
 		if !mc {
 			f.xmlAttr[path] = append(f.xmlAttr[path], SourceRelationshipCompatibility)
 		}
-		if !ignore {
+		if ignore == -1 {
 			f.xmlAttr[path] = append(f.xmlAttr[path], xml.Attr{
 				Name:  xml.Name{Local: "Ignorable", Space: "mc"},
 				Value: ns.Name.Local,
 			})
+			return
 		}
+		f.setIgnorableNameSpace(path, ignore, ns)
+	}
+}
+
+// setIgnorableNameSpace provides a function to set XML namespace as ignorable by the given
+// attribute.
+func (f *File) setIgnorableNameSpace(path string, index int, ns xml.Attr) {
+	ignorableNS := []string{"c14", "cdr14", "a14", "pic14", "x14", "xdr14", "x14ac", "dsp", "mso14", "dgm14", "x15", "x12ac", "x15ac", "xr", "xr2", "xr3", "xr4", "xr5", "xr6", "xr7", "xr8", "xr9", "xr10", "xr11", "xr12", "xr13", "xr14", "xr15", "x15", "x16", "x16r2", "mo", "mx", "mv", "o", "v"}
+	if inStrSlice(strings.Fields(f.xmlAttr[path][index].Value), ns.Name.Local) == -1 && inStrSlice(ignorableNS, ns.Name.Local) != -1 {
+		f.xmlAttr[path][index].Value = strings.TrimSpace(fmt.Sprintf("%s %s", f.xmlAttr[path][index].Value, ns.Name.Local))
 	}
 }
 

lib_test.go

@@ -1,6 +1,7 @@
 package excelize
 
 import (
+	"encoding/xml"
 	"fmt"
 	"strconv"
 	"strings"
@@ -215,6 +216,13 @@ func TestBytesReplace(t *testing.T) {
 	assert.EqualValues(t, s, bytesReplace(s, []byte{}, []byte{}, 0))
 }
 
+func TestSetIgnorableNameSpace(t *testing.T) {
+	f := NewFile()
+	f.xmlAttr["xml_path"] = []xml.Attr{{}}
+	f.setIgnorableNameSpace("xml_path", 0, xml.Attr{Name: xml.Name{Local: "c14"}})
+	assert.EqualValues(t, "c14", f.xmlAttr["xml_path"][0].Value)
+}
+
 func TestStack(t *testing.T) {
 	s := NewStack()
 	assert.Equal(t, s.Peek(), nil)