This closes #2205, fix string counting and truncation for cell length limitation (#2206)

Author: torotake

calc.go

@@ -29,6 +29,7 @@ import (
 	"sync"
 	"time"
 	"unicode"
+	"unicode/utf16"
 	"unicode/utf8"
 	"unsafe"
 
@@ -14366,7 +14367,7 @@ func (fn *formulaFuncs) TEXTJOIN(argsList *list.List) formulaArg {
 		return ok
 	}
 	result := strings.Join(args, delimiter.Value())
-	if len(result) > TotalCellChars {
+	if len(utf16.Encode([]rune(result))) > TotalCellChars {
 		return newErrorFormulaArg(formulaErrorVALUE, fmt.Sprintf("TEXTJOIN function exceeds %d characters", TotalCellChars))
 	}
 	return newStringFormulaArg(result)

calc_test.go

@@ -3969,6 +3969,7 @@ func TestCalcCellValue(t *testing.T) {
 		"TEXTJOIN(\"\",TRUE,NA())": {"#N/A", "#N/A"},
 		"TEXTJOIN(\"\",TRUE," + strings.Repeat("0,", 250) + ",0)": {"#VALUE!", "TEXTJOIN accepts at most 252 arguments"},
 		"TEXTJOIN(\",\",FALSE,REPT(\"*\",32768))":                 {"#VALUE!", "TEXTJOIN function exceeds 32767 characters"},
+		"TEXTJOIN(\"\",FALSE,REPT(\"\U0001F600\",16384))":         {"#VALUE!", "TEXTJOIN function exceeds 32767 characters"},
 		// TRIM
 		"TRIM()":    {"#VALUE!", "TRIM requires 1 argument"},
 		"TRIM(1,2)": {"#VALUE!", "TRIM requires 1 argument"},

cell.go

@@ -21,7 +21,7 @@ import (
 	"strconv"
 	"strings"
 	"time"
-	"unicode/utf8"
+	"unicode/utf16"
 
 	"github.com/xuri/efp"
 )
@@ -447,8 +447,8 @@ func (f *File) SetCellStr(sheet, cell, value string) error {
 
 // setCellString provides a function to set string type to shared string table.
 func (f *File) setCellString(value string) (t, v string, err error) {
-	if utf8.RuneCountInString(value) > TotalCellChars {
-		value = string([]rune(value)[:TotalCellChars])
+	if len(utf16.Encode([]rune(value))) > TotalCellChars {
+		value = truncateUTF16Units(value, TotalCellChars)
 	}
 	t = "s"
 	var si int
@@ -510,8 +510,8 @@ func (f *File) setSharedString(val string) (int, error) {
 
 // trimCellValue provides a function to set string type to cell.
 func trimCellValue(value string, escape bool) (v string, ns xml.Attr) {
-	if utf8.RuneCountInString(value) > TotalCellChars {
-		value = string([]rune(value)[:TotalCellChars])
+	if len(utf16.Encode([]rune(value))) > TotalCellChars {
+		value = truncateUTF16Units(value, TotalCellChars)
 	}
 	if value != "" {
 		prefix, suffix := value[0], value[len(value)-1]
@@ -1211,7 +1211,7 @@ func setRichText(runs []RichTextRun) ([]xlsxR, error) {
 		totalCellChars int
 	)
 	for _, textRun := range runs {
-		totalCellChars += utf8.RuneCountInString(textRun.Text)
+		totalCellChars += len(utf16.Encode([]rune(textRun.Text)))
 		if totalCellChars > TotalCellChars {
 			return textRuns, ErrCellCharsLength
 		}

lib.go

@@ -25,6 +25,7 @@ import (
 	"regexp"
 	"strconv"
 	"strings"
+	"unicode/utf16"
 )
 
 // ReadZipReader extract spreadsheet with given options.
@@ -940,6 +941,18 @@ func setPtrFieldsVal(fields []string, immutable, mutable reflect.Value) {
 	}
 }
 
+// truncateUTF16Units truncates a string to a maximum number of UTF-16 code
+// units.
+func truncateUTF16Units(s string, length int) string {
+	var cnt int
+	for i, r := range s {
+		if cnt += utf16.RuneLen(r); cnt > length {
+			return s[:i]
+		}
+	}
+	return s
+}
+
 // Stack defined an abstract data type that serves as a collection of elements.
 type Stack struct {
 	list *list.List

lib_test.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"sync"
 	"testing"
+	"unicode/utf16"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -353,6 +354,28 @@ func TestBstrMarshal(t *testing.T) {
 	}
 }
 
+func TestTruncateUTF16Units(t *testing.T) {
+	assertTrunc := func(s string, max int, expected string) {
+		assert.Equal(t, expected, truncateUTF16Units(s, max), "src=%q max=%d", s, max)
+		assert.LessOrEqual(t, len(utf16.Encode([]rune(truncateUTF16Units(s, max)))), max)
+	}
+	// No truncation
+	assertTrunc("ABC", 3, "ABC")
+	assertTrunc("A\U0001F600B", 4, "A\U0001F600B")
+	// Truncate cutting before BMP rune
+	assertTrunc("ABCDE", 3, "ABC")
+	// Truncate with surrogate pair boundary: keep pair intact
+	assertTrunc("A\U0001F600B", 3, "A\U0001F600") // 1 + 2 units
+	assertTrunc("A\U0001F600B", 2, "A")           // pair would overflow
+	assertTrunc("\U0001F600B", 1, "")             // first rune (2 units) exceeds limit
+	assertTrunc("\U0001F600B", 2, "\U0001F600")   // exact fit
+	assertTrunc("\U0001F600B", 3, "\U0001F600B")  // allow extra
+	// Multiple surrogate pairs
+	assertTrunc("\U0001F600\U0001F600B", 2, "\U0001F600")           // corrected expectation per logic
+	assertTrunc("\U0001F600\U0001F600B", 3, "\U0001F600")           // 2 units kept, next pair would exceed
+	assertTrunc("\U0001F600\U0001F600B", 4, "\U0001F600\U0001F600") // both pairs (4 units)
+}
+
 func TestReadBytes(t *testing.T) {
 	f := &File{tempFiles: sync.Map{}}
 	sheet := "xl/worksheets/sheet1.xml"

sheet.go

@@ -25,7 +25,6 @@ import (
 	"strconv"
 	"strings"
 	"unicode/utf16"
-	"unicode/utf8"
 
 	"github.com/tiendc/go-deepcopy"
 )
@@ -1485,7 +1484,7 @@ func checkSheetName(name string) error {
 	if name == "" {
 		return ErrSheetNameBlank
 	}
-	if utf8.RuneCountInString(name) > MaxSheetNameLength {
+	if len(utf16.Encode([]rune(name))) > MaxSheetNameLength {
 		return ErrSheetNameLength
 	}
 	if strings.HasPrefix(name, "'") || strings.HasSuffix(name, "'") {

sheet_test.go

@@ -762,22 +762,28 @@ func TestSetSheetBackgroundFromBytes(t *testing.T) {
 }
 
 func TestCheckSheetName(t *testing.T) {
-	// Test valid sheet name
-	assert.NoError(t, checkSheetName("Sheet1"))
-	assert.NoError(t, checkSheetName("She'et1"))
-	// Test invalid sheet name, empty name
-	assert.EqualError(t, checkSheetName(""), ErrSheetNameBlank.Error())
-	// Test invalid sheet name, include :\/?*[]
-	assert.EqualError(t, checkSheetName("Sheet:"), ErrSheetNameInvalid.Error())
-	assert.EqualError(t, checkSheetName(`Sheet\`), ErrSheetNameInvalid.Error())
-	assert.EqualError(t, checkSheetName("Sheet/"), ErrSheetNameInvalid.Error())
-	assert.EqualError(t, checkSheetName("Sheet?"), ErrSheetNameInvalid.Error())
-	assert.EqualError(t, checkSheetName("Sheet*"), ErrSheetNameInvalid.Error())
-	assert.EqualError(t, checkSheetName("Sheet["), ErrSheetNameInvalid.Error())
-	assert.EqualError(t, checkSheetName("Sheet]"), ErrSheetNameInvalid.Error())
-	// Test invalid sheet name, single quotes at the front or at the end
-	assert.EqualError(t, checkSheetName("'Sheet"), ErrSheetNameSingleQuote.Error())
-	assert.EqualError(t, checkSheetName("Sheet'"), ErrSheetNameSingleQuote.Error())
+	for expected, name := range map[error]string{
+		// Test valid sheet name
+		nil: "Sheet1",
+		nil: "She'et1",
+		// Test invalid sheet name, empty name
+		ErrSheetNameBlank: "",
+		// Test invalid sheet name, include :\/?*[]
+		ErrSheetNameInvalid: "Sheet:",
+		ErrSheetNameInvalid: `Sheet\`,
+		ErrSheetNameInvalid: "Sheet/",
+		ErrSheetNameInvalid: "Sheet?",
+		ErrSheetNameInvalid: "Sheet*",
+		ErrSheetNameInvalid: "Sheet[",
+		ErrSheetNameInvalid: "Sheet]",
+		// Test invalid sheet name, single quotes at the front or at the end
+		ErrSheetNameSingleQuote: "'Sheet",
+		ErrSheetNameSingleQuote: "Sheet'",
+		// Test invalid sheet name, exceed max length
+		ErrSheetNameLength: "Sheet" + strings.Repeat("\U0001F600", 14),
+	} {
+		assert.Equal(t, expected, checkSheetName(name))
+	}
 }
 
 func TestSheetDimension(t *testing.T) {