Fix for #1533 (#1534)

Code assumes that formula whose result starts with # indicates error.
Change to check entire result against error list in Functions.

src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php

@@ -1112,7 +1112,7 @@ private function writeCellFormula(XMLWriter $objWriter, string $cellValue, Cell
     {
         $calculatedValue = $this->getParentWriter()->getPreCalculateFormulas() ? $pCell->getCalculatedValue() : $cellValue;
         if (is_string($calculatedValue)) {
-            if (substr($calculatedValue, 0, 1) === '#') {
+            if (\PhpOffice\PhpSpreadsheet\Calculation\Functions::isError($calculatedValue)) {
                 $this->writeCellError($objWriter, 'e', $cellValue, $calculatedValue);
 
                 return;

tests/PhpSpreadsheetTests/Writer/Xlsx/StartsWithHashTest.php

@@ -0,0 +1,62 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Writer\Xlsx;
+
+use PhpOffice\PhpSpreadsheet\Cell\DataType;
+use PhpOffice\PhpSpreadsheet\Reader\Xlsx as Reader;
+use PhpOffice\PhpSpreadsheet\Settings;
+use PhpOffice\PhpSpreadsheet\Shared\File;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Writer\Xlsx as Writer;
+use PHPUnit\Framework\TestCase;
+use ZipArchive;
+
+class StartsWithHashTest extends TestCase
+{
+    public function testStartWithHash(): void
+    {
+        $outputFilename = tempnam(File::sysGetTempDir(), 'phpspreadsheet-test');
+        Settings::setLibXmlLoaderOptions(null);
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->setCellValueExplicit('A1', '#define M', DataType::TYPE_STRING);
+        $sheet->setCellValue('A2', '=A1');
+        $sheet->setCellValue('A3', '=UNKNOWNFUNC()');
+
+        $writer = new Writer($spreadsheet);
+        $writer->save($outputFilename);
+
+        $reader = new Reader();
+        $sheet = $reader->load($outputFilename);
+        unlink($outputFilename);
+
+        self::assertSame('#define M', $sheet->getActiveSheet()->getCell('A1')->getValue());
+        self::assertSame('#define M', $sheet->getActiveSheet()->getCell('A2')->getCalculatedValue());
+        self::assertSame('f', $sheet->getActiveSheet()->getCell('A3')->getDataType());
+        self::assertSame('#NAME?', $sheet->getActiveSheet()->getCell('A3')->getCalculatedValue());
+        self::assertSame('f', $sheet->getActiveSheet()->getCell('A3')->getDataType());
+    }
+
+    public function testStartWithHashReadRaw(): void
+    {
+        // Make sure raw data indicates A3 is an error, but A2 isn't.
+        $outputFilename = tempnam(File::sysGetTempDir(), 'phpspreadsheet-test');
+        Settings::setLibXmlLoaderOptions(null);
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->setCellValueExplicit('A1', '#define M', DataType::TYPE_STRING);
+        $sheet->setCellValue('A2', '=A1');
+        $sheet->setCellValue('A3', '=UNKNOWNFUNC()');
+
+        $writer = new Writer($spreadsheet);
+        $writer->save($outputFilename);
+        $zip = new ZipArchive();
+        $zip->open($outputFilename);
+        $resultSheet1Raw = $zip->getFromName('xl/worksheets/sheet1.xml');
+        $zip->close();
+        unlink($outputFilename);
+
+        self::assertStringContainsString('<c r="A3" t="e">', $resultSheet1Raw);
+        self::assertStringContainsString('<c r="A2" t="str">', $resultSheet1Raw);
+    }
+}