fix: Set font size to 10 when given 0

CHANGELOG.md

@@ -42,6 +42,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 - Fixed issue with Xlsx@listWorksheetInfo not returning any data
 - Fixed invalid arguments triggering mb_substr() error in LEFT(), MID() and RIGHT() text functions. [Issue #640](https://github.com/PHPOffice/PhpSpreadsheet/issues/640)
 - Fix for [Issue #1916](https://github.com/PHPOffice/PhpSpreadsheet/issues/1916) - Invalid signature check for XML files
+- Fix change in `Font::setSize()` behavior for PHP8. [PR #2100](https://github.com/PHPOffice/PhpSpreadsheet/pull/2100)
 
 ## 1.17.1 - 2021-03-01
 

src/PhpSpreadsheet/Style/Font.php

@@ -249,15 +249,22 @@ public function getSize()
     /**
      * Set Size.
      *
-     * @param float $pValue
+     * @param mixed $pValue A float representing the value of a positive measurement in points (1/72 of an inch)
      *
      * @return $this
      */
     public function setSize($pValue)
     {
-        if ($pValue == '') {
-            $pValue = 10;
+        if (is_string($pValue) || is_int($pValue)) {
+            $pValue = (float) $pValue; // $pValue = 0 if given string is not numeric
+        }
+
+        // Size must be a positive floating point number
+        // ECMA-376-1:2016, part 1, chapter 18.4.11 sz (Font Size), p. 1536
+        if (!is_float($pValue) || !($pValue > 0)) {
+            $pValue = 10.0;
         }
+
         if ($this->isSupervisor) {
             $styleArray = $this->getStyleArray(['size' => $pValue]);
             $this->getActiveSheet()->getStyle($this->getSelectedCells())->applyFromArray($styleArray);

tests/PhpSpreadsheetTests/Style/FontTest.php

@@ -39,4 +39,36 @@ public function testSuperSubScript(): void
         self::assertTrue($font->getSuperscript());
         self::assertFalse($font->getSubscript(), 'False remains unchanged');
     }
+
+    public function testSize(): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet = $spreadsheet->getActiveSheet();
+        $cell = $sheet->getCell('A1');
+        $cell->setValue('Cell A1');
+        $font = $cell->getStyle()->getFont();
+
+        self::assertEquals(11, $font->getSize(), 'The default is 11');
+
+        $font->setSize(12);
+        self::assertEquals(12, $font->getSize(), 'Accepted new font size');
+
+        $invalidFontSizeValues = [
+            '',
+            false,
+            true,
+            'non_numeric_string',
+            '-1.0',
+            -1.0,
+            0,
+            [],
+            (object) [],
+            null,
+        ];
+        foreach ($invalidFontSizeValues as $invalidFontSizeValue) {
+            $font->setSize(12);
+            $font->setSize($invalidFontSizeValue);
+            self::assertEquals(10, $font->getSize(), 'Set to 10 after trying to set an invalid value.');
+        }
+    }
 }