add empty sharedStrings.xml file

There should be no need, but it might help some readers.

Author: alicebob

contenttypes.go

@@ -6,12 +6,13 @@ import (
 )
 
 func writeContentTypes(fh io.Writer, sheetCount int) error {
-	fh.Write([]byte(`<?xml version="1.0" encoding="UTF-8"?>
+	fh.Write([]byte(`<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
 <Types xmlns="http://schemas.openxmlformats.org/package/2006/content-types">
-<Override PartName="/_rels/.rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"></Override>
-<Override PartName="/xl/_rels/workbook.xml.rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"></Override>
-<Override PartName="/xl/styles.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml"></Override>
-<Override PartName="/xl/workbook.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"></Override>
+<Override PartName="/_rels/.rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>
+<Override PartName="/xl/_rels/workbook.xml.rels" ContentType="application/vnd.openxmlformats-package.relationships+xml"/>
+<Override PartName="/xl/styles.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.styles+xml"/>
+<Override PartName="/xl/workbook.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.main+xml"/>
+<Override PartName="/xl/sharedStrings.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.sharedStrings+xml"/>
 `))
 	for i := 0; i < sheetCount; i++ {
 		fmt.Fprintf(fh, `<Override PartName="/xl/worksheets/sheet%d.xml" ContentType="application/vnd.openxmlformats-officedocument.spreadsheetml.worksheet+xml"></Override>`,

relations.go

@@ -36,6 +36,11 @@ func writeWorkbookRelations(fh io.Writer, sheetTitles []string) error {
 			Target: "/xl/styles.xml",
 			Type:   "http://schemas.openxmlformats.org/officeDocument/2006/relationships/styles",
 		},
+		{
+			ID:     "shared1",
+			Target: "/xl/sharedStrings.xml",
+			Type:   "http://schemas.openxmlformats.org/officeDocument/2006/relationships/sharedStrings",
+		},
 	}
 	for i := range sheetTitles {
 		rels = append(rels, relationship{

sharedstrings.go

@@ -0,0 +1,14 @@
+package streamxlsx
+
+import (
+	"io"
+)
+
+// we don't use shared strings, but we make an empty file just in case some
+// excel version expects one
+func writeSharedStrings(fh io.Writer) error {
+	_, err := fh.Write([]byte(`<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<sst xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" count="0" uniqueCount="0"></sst>
+`))
+	return err
+}

streamxlsx.go

@@ -152,6 +152,9 @@ func (s *StreamXLSX) Close() error {
 	if err := s.writeStylesheet(); err != nil {
 		return err
 	}
+	if err := s.writeSharedStrings(); err != nil {
+		return err
+	}
 	if err := s.writeWorkbookRelations(); err != nil {
 		return err
 	}
@@ -201,6 +204,15 @@ func (s *StreamXLSX) writeStylesheet() error {
 	return writeStylesheet(fh, s.Styles)
 }
 
+func (s *StreamXLSX) writeSharedStrings() error {
+	filename := "xl/sharedStrings.xml"
+	fh, err := s.zip.Create(filename)
+	if err != nil {
+		return err
+	}
+	return writeSharedStrings(fh)
+}
+
 func (s *StreamXLSX) writeRelations() error {
 	filename := "_rels/.rels"
 	fh, err := s.zip.Create(filename)