Prepare to Deprecate Optionality of Second Arg to Cell::setValueExplicit

In PR #4716, @RobinvanderVliet points out that Cell::setValueExplicit and Worksheet::setCellValueExplicit are strangely inconsistent, where the latter requires you to specify a DataType but the former does not. The fix in that PR is to make the latter offer a default DataType rather than requiring the parameter. While that does eliminate inconsistency, I think it does so in the wrong direction - the solution should be to eliminate the optionality in the former - an implicit value for setValueExplicit just doesn't make sense. We can't do that without a breaking change, which this is not. However, we can update the doc-block and change log to indicate our intention to make that change in the next breaking release.

tests/PhpSpreadsheetTests/Worksheet/SetValueExplicitWorksheetTest.php

@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace PhpOffice\PhpSpreadsheetTests\Worksheet;
+
+use ArgumentCountError;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+use ReflectionMethod;
+
+class SetValueExplicitWorksheetTest extends TestCase
+{
+    protected string $method = 'setCellValueExplicit';
+
+    protected int $requiredParameters = 3;
+
+    public function testRequired(): void
+    {
+        $reflectionMethod = new ReflectionMethod(Worksheet::class, $this->method);
+        $requiredParameters = $reflectionMethod->getNumberOfRequiredParameters();
+        self::assertSame($this->requiredParameters, $requiredParameters);
+    }
+
+    public static function setCellValueExplicitTypeArgumentProvider(): array
+    {
+        return require 'tests/data/Cell/SetValueExplicitTypeArguments.php';
+    }
+
+    #[DataProvider('setCellValueExplicitTypeArgumentProvider')]
+    public function testSetCellValueExplicitTypeArgumentHandling(
+        mixed $value,
+        ?string $dataType,
+        mixed $expectedValue,
+        string $expectedDataType
+    ): void {
+        $spreadsheet = new Spreadsheet();
+        $worksheet = $spreadsheet->getActiveSheet();
+        $coordinate = 'A1';
+        $cell = $worksheet->getCell($coordinate);
+
+        try {
+            if ($dataType) {
+                $worksheet->{$this->method}($coordinate, $value, $dataType);
+            } else {
+                $worksheet->{$this->method}($coordinate, $value);
+                self::assertSame(2, $this->requiredParameters);
+            }
+            self::assertSame($expectedValue, $cell->getValue());
+            self::assertSame($expectedDataType, $cell->getDataType());
+        } catch (ArgumentCountError) {
+            self::assertSame(3, $this->requiredParameters);
+            self::assertNull($dataType);
+        }
+
+        $spreadsheet->disconnectWorksheets();
+    }
+}