Change Style Without Affecting Current Cell/Sheet, and Invalid Formulas

Fix PHPOffice#1310, which was closed as stale in 2020, but which I will now reopen. Supersedes PR PHPOffice#1311 (@jaiminmoslake7020), from which I will remove the stale label but leave closed. The issue and the PR were too limited  - they detected that the use of two equal signs at the start of a string made for an invalid formula, but there are variations, trivial and otherwise, which might also be detected. Using `setValue` with a string which starts with an equal sign will now attempt to parse (not evaluate) the formula; for certain situations in which the parser throws an exception, the string will be treated as a string rather than a formula. An example where it will still be treated as a formula is a 3D range reference, where the problem is not that it can't be parsed, but rather that the formula isn't supported (see unit test Calculation/Engine/RangeTest::test3dRangeEvaluation). Allowing such a formula might cause problems later on, but that is already what happens.

A string beginning with an equal sign but which isn't treated as a formula will automatically set the `quotePrefix` attribute to `true`; all other `setValue` attempts will set it to `false`. This avoids the problem of a lingering value causing problems later on.

It has long been a matter of discontent that setting a style can change the selected cells. A new method is added to `Worksheet`:
```php
applyStylesFromArray(string $coordinate, array $styleArray)
```
This will attempt to guarantee that the active sheet in the current spreadsheet, and the selected cells in the current worksheet, remain undisturbed after the call. The setting of `quotePrefix` above is the first use of the new method.

src/PhpSpreadsheet/Calculation/Calculation.php

@@ -4065,7 +4065,7 @@ private function internalParseFormula(string $formula, ?Cell $cell = null): bool
             $opCharacter = $formula[$index]; //    Get the first character of the value at the current index position
 
             // Check for two-character operators (e.g. >=, <=, <>)
-            if ((isset(self::$comparisonOperators[$opCharacter])) && (strlen($formula) > $index) && (isset(self::$comparisonOperators[$formula[$index + 1]]))) {
+            if ((isset(self::$comparisonOperators[$opCharacter])) && (strlen($formula) > $index) && isset($formula[$index + 1], self::$comparisonOperators[$formula[$index + 1]])) {
                 $opCharacter .= $formula[++$index];
             }
             //    Find out if we're currently at the beginning of a number, variable, cell/row/column reference,

src/PhpSpreadsheet/Cell/Cell.php

@@ -248,6 +248,7 @@ public function setValue(mixed $value, ?IValueBinder $binder = null): self
     public function setValueExplicit(mixed $value, string $dataType = DataType::TYPE_STRING): self
     {
         $oldValue = $this->value;
+        $quotePrefix = false;
 
         // set the value according to data type
         switch ($dataType) {
@@ -260,6 +261,10 @@ public function setValueExplicit(mixed $value, string $dataType = DataType::TYPE
                 // no break
             case DataType::TYPE_STRING:
                 // Synonym for string
+                if (is_string($value) && strlen($value) > 1 && $value[0] === '=') {
+                    $quotePrefix = true;
+                }
+                // no break
             case DataType::TYPE_INLINE:
                 // Rich text
                 $this->value = DataType::checkString($value);
@@ -299,6 +304,7 @@ public function setValueExplicit(mixed $value, string $dataType = DataType::TYPE
         $this->updateInCollection();
         $cellCoordinate = $this->getCoordinate();
         self::updateIfCellIsTableHeader($this->getParent()?->getParent(), $this, $oldValue, $value);
+        $this->getWorksheet()->applyStylesFromArray($cellCoordinate, ['quotePrefix' => $quotePrefix]);
 
         return $this->getParent()?->get($cellCoordinate) ?? $this;
     }

src/PhpSpreadsheet/Cell/DefaultValueBinder.php

@@ -3,6 +3,8 @@
 namespace PhpOffice\PhpSpreadsheet\Cell;
 
 use DateTimeInterface;
+use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
+use PhpOffice\PhpSpreadsheet\Calculation\Exception as CalculationException;
 use PhpOffice\PhpSpreadsheet\Exception as SpreadsheetException;
 use PhpOffice\PhpSpreadsheet\RichText\RichText;
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
@@ -46,17 +48,40 @@ public static function dataTypeForValue(mixed $value): string
         // Match the value against a few data types
         if ($value === null) {
             return DataType::TYPE_NULL;
-        } elseif (is_float($value) || is_int($value)) {
+        }
+        if (is_float($value) || is_int($value)) {
             return DataType::TYPE_NUMERIC;
-        } elseif (is_bool($value)) {
+        }
+        if (is_bool($value)) {
             return DataType::TYPE_BOOL;
-        } elseif ($value === '') {
+        }
+        if ($value === '') {
             return DataType::TYPE_STRING;
-        } elseif ($value instanceof RichText) {
+        }
+        if ($value instanceof RichText) {
             return DataType::TYPE_INLINE;
-        } elseif (is_string($value) && strlen($value) > 1 && $value[0] === '=') {
+        }
+        if (is_string($value) && strlen($value) > 1 && $value[0] === '=') {
+            $calculation = new Calculation();
+            $calculation->disableBranchPruning();
+
+            try {
+                if (empty($calculation->parseFormula($value))) {
+                    return DataType::TYPE_STRING;
+                }
+            } catch (CalculationException $e) {
+                $message = $e->getMessage();
+                if (
+                    $message === 'Formula Error: An unexpected error occurred'
+                    || str_contains($message, 'has no operands')
+                ) {
+                    return DataType::TYPE_STRING;
+                }
+            }
+
             return DataType::TYPE_FORMULA;
-        } elseif (preg_match('/^[\+\-]?(\d+\\.?\d*|\d*\\.?\d+)([Ee][\-\+]?[0-2]?\d{1,3})?$/', $value)) {
+        }
+        if (preg_match('/^[\+\-]?(\d+\\.?\d*|\d*\\.?\d+)([Ee][\-\+]?[0-2]?\d{1,3})?$/', $value)) {
             $tValue = ltrim($value, '+-');
             if (is_string($value) && strlen($tValue) > 1 && $tValue[0] === '0' && $tValue[1] !== '.') {
                 return DataType::TYPE_STRING;
@@ -67,7 +92,8 @@ public static function dataTypeForValue(mixed $value): string
             }
 
             return DataType::TYPE_NUMERIC;
-        } elseif (is_string($value)) {
+        }
+        if (is_string($value)) {
             $errorCodes = DataType::getErrorCodes();
             if (isset($errorCodes[$value])) {
                 return DataType::TYPE_ERROR;

src/PhpSpreadsheet/Cell/StringValueBinder.php

@@ -8,7 +8,7 @@
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
 use Stringable;
 
-class StringValueBinder implements IValueBinder
+class StringValueBinder extends DefaultValueBinder implements IValueBinder
 {
     protected bool $convertNull = true;
 
@@ -87,12 +87,9 @@ public function bindValue(Cell $cell, mixed $value): bool
             $cell->setValueExplicit($value, DataType::TYPE_BOOL);
         } elseif ((is_int($value) || is_float($value)) && $this->convertNumeric === false) {
             $cell->setValueExplicit($value, DataType::TYPE_NUMERIC);
-        } elseif (is_string($value) && strlen($value) > 1 && $value[0] === '=' && $this->convertFormula === false) {
+        } elseif (is_string($value) && strlen($value) > 1 && $value[0] === '=' && $this->convertFormula === false && parent::dataTypeForValue($value) === DataType::TYPE_FORMULA) {
             $cell->setValueExplicit($value, DataType::TYPE_FORMULA);
         } else {
-            if (is_string($value) && strlen($value) > 1 && $value[0] === '=') {
-                $cell->getStyle()->setQuotePrefix(true);
-            }
             $cell->setValueExplicit((string) $value, DataType::TYPE_STRING);
         }
 

src/PhpSpreadsheet/Worksheet/Worksheet.php

@@ -3673,4 +3673,19 @@ public function copyCells(string $fromCell, string $toCells, bool $copyStyle = t
             }
         }
     }
+
+    public function applyStylesFromArray(string $coordinate, array $styleArray): bool
+    {
+        $spreadsheet = $this->parent;
+        if ($spreadsheet === null) {
+            return false;
+        }
+        $activeSheetIndex = $spreadsheet->getActiveSheetIndex();
+        $originalSelected = $this->selectedCells;
+        $this->getStyle($coordinate)->applyFromArray($styleArray);
+        $this->selectedCells = $originalSelected;
+        $spreadsheet->setActiveSheetIndex($activeSheetIndex);
+
+        return true;
+    }
 }

tests/PhpSpreadsheetTests/Calculation/Engine/RangeTest.php

@@ -4,6 +4,7 @@
 
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Engine;
 
+use PhpOffice\PhpSpreadsheet\Calculation\Calculation;
 use PhpOffice\PhpSpreadsheet\Calculation\Information\ExcelError;
 use PhpOffice\PhpSpreadsheet\NamedRange;
 use PhpOffice\PhpSpreadsheet\Spreadsheet;
@@ -13,20 +14,31 @@ class RangeTest extends TestCase
 {
     private string $incompleteMessage = 'Must be revisited';
 
-    private Spreadsheet $spreadSheet;
+    private ?Spreadsheet $spreadSheet = null;
 
-    protected function setUp(): void
+    protected function getSpreadsheet(): Spreadsheet
     {
-        $this->spreadSheet = new Spreadsheet();
-        $this->spreadSheet->getActiveSheet()
+        $spreadsheet = new Spreadsheet();
+        $spreadsheet->getActiveSheet()
             ->fromArray(array_chunk(range(1, 240), 6), null, 'A1', true);
+
+        return $spreadsheet;
+    }
+
+    protected function tearDown(): void
+    {
+        if ($this->spreadSheet !== null) {
+            $this->spreadSheet->disconnectWorksheets();
+            $this->spreadSheet = null;
+        }
     }
 
     /**
      * @dataProvider providerRangeEvaluation
      */
     public function testRangeEvaluation(string $formula, int|string $expectedResult): void
     {
+        $this->spreadSheet = $this->getSpreadsheet();
         $workSheet = $this->spreadSheet->getActiveSheet();
         $workSheet->setCellValue('H1', $formula);
 
@@ -64,8 +76,20 @@ public static function providerRangeEvaluation(): array
         ];
     }
 
+    public function test3dRangeParsing(): void
+    {
+        // This test shows that parsing throws exception.
+        // Next test shows that formula is still treated as a formula
+        //     despite the parse failure.
+        $this->expectExceptionMessage('3D Range references are not yet supported');
+        $calculation = new Calculation();
+        $calculation->disableBranchPruning();
+        $calculation->parseFormula('=SUM(Worksheet!A1:Worksheet2!B3');
+    }
+
     public function test3dRangeEvaluation(): void
     {
+        $this->spreadSheet = $this->getSpreadsheet();
         $workSheet = $this->spreadSheet->getActiveSheet();
         $workSheet->setCellValue('E1', '=SUM(Worksheet!A1:Worksheet2!B3)');
 
@@ -78,6 +102,7 @@ public function test3dRangeEvaluation(): void
      */
     public function testNamedRangeEvaluation(array $ranges, string $formula, int $expectedResult): void
     {
+        $this->spreadSheet = $this->getSpreadsheet();
         $workSheet = $this->spreadSheet->getActiveSheet();
         foreach ($ranges as $id => $range) {
             $this->spreadSheet->addNamedRange(new NamedRange('GROUP' . ++$id, $workSheet, $range));
@@ -116,6 +141,7 @@ public static function providerNamedRangeEvaluation(): array
      */
     public function testUTF8NamedRangeEvaluation(array $names, array $ranges, string $formula, int $expectedResult): void
     {
+        $this->spreadSheet = $this->getSpreadsheet();
         $workSheet = $this->spreadSheet->getActiveSheet();
         foreach ($names as $index => $name) {
             $range = $ranges[$index];
@@ -144,6 +170,7 @@ public function testCompositeNamedRangeEvaluation(string $composite, int $expect
         if ($this->incompleteMessage !== '') {
             self::markTestIncomplete($this->incompleteMessage);
         }
+        $this->spreadSheet = $this->getSpreadsheet();
 
         $workSheet = $this->spreadSheet->getActiveSheet();
         $this->spreadSheet->addNamedRange(new NamedRange('COMPOSITE', $workSheet, $composite));

tests/PhpSpreadsheetTests/Cell/AdvancedValueBinderTest.php

@@ -6,6 +6,7 @@
 
 use PhpOffice\PhpSpreadsheet\Cell\AdvancedValueBinder;
 use PhpOffice\PhpSpreadsheet\Cell\Cell;
+use PhpOffice\PhpSpreadsheet\Cell\DataType;
 use PhpOffice\PhpSpreadsheet\Cell\IValueBinder;
 use PhpOffice\PhpSpreadsheet\Settings;
 use PhpOffice\PhpSpreadsheet\Shared\StringHelper;
@@ -232,4 +233,31 @@ public static function stringProvider(): array
             ["Hello\nWorld", true],
         ];
     }
+
+    /**
+     * @dataProvider formulaProvider
+     */
+    public function testFormula(string $value, string $dataType): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+
+        $sheet->getCell('A1')->setValue($value);
+        self::assertSame($dataType, $sheet->getCell('A1')->getDataType());
+        if ($dataType === DataType::TYPE_FORMULA) {
+            self::assertFalse($sheet->getStyle('A1')->getQuotePrefix());
+        } else {
+            self::assertTrue($sheet->getStyle('A1')->getQuotePrefix());
+        }
+
+        $spreadsheet->disconnectWorksheets();
+    }
+
+    public static function formulaProvider(): array
+    {
+        return [
+            'normal formula' => ['=SUM(A1:C3)', DataType::TYPE_FORMULA],
+            'issue 1310' => ['======', DataType::TYPE_STRING],
+        ];
+    }
 }

tests/PhpSpreadsheetTests/Cell/StringValueBinderTest.php

@@ -211,13 +211,19 @@ public function testStringValueBinderSuppressFormulaConversion(
         $cell->setValue($value);
         self::assertSame($expectedValue, $cell->getValue());
         self::assertSame($expectedDataType, $cell->getDataType());
+        if ($expectedDataType === DataType::TYPE_FORMULA) {
+            self::assertFalse($sheet->getStyle('A1')->getQuotePrefix());
+        } else {
+            self::assertTrue($sheet->getStyle('A1')->getQuotePrefix());
+        }
         $spreadsheet->disconnectWorksheets();
     }
 
     public static function providerDataValuesSuppressFormulaConversion(): array
     {
         return [
-            ['=SUM(A1:C3)', '=SUM(A1:C3)', DataType::TYPE_FORMULA, false],
+            'normal formula' => ['=SUM(A1:C3)', '=SUM(A1:C3)', DataType::TYPE_FORMULA],
+            'issue 1310' => ['======', '======', DataType::TYPE_STRING],
         ];
     }
 

tests/data/Cell/DefaultValueBinder.php

@@ -83,4 +83,7 @@
         's',
         '1234567890123459012345689012345690',
     ],
+    'Issue 1310 Multiple = at start' => ['s', '======'],
+    'Issue 1310 Variant 1' => ['s', '= ====='],
+    'Issue 1310 Variant 2' => ['s', '=2*3='],
 ];