fix(filter): normalize requiredFilters to array in Filter constructor

When the `requires` parameter of a `#drilldowninfo` filter is set, the
value was stored as a plain string. The `foreach` loop in
`SpecialBrowseData::createDrilldownQuery()` that checks required filters
then iterated over individual characters instead of filter names, so
no character ever matched a filter name and the filter was permanently
hidden rather than appearing once its required filter was applied.

Fix by wrapping a string value in a single-element array in
`Filter::__construct()`, so `requiredFilters()` always returns an array.

Author: gesinn-it-gea

CHANGELOG.md

@@ -6,6 +6,9 @@ This project adheres to [Semantic Versioning](https://semver.org/) and
 
 ## [Unreleased]
 
+### Fixed
+- Fix `requires` filter option having no effect: filters with `requires=SomeFilter` were never shown because the required-filter name was iterated as individual characters instead of as a filter name ([#4](https://github.com/SemanticMediaWiki/SemanticDrilldown/issues/4))
+
 ### Changed
 - Replace global config access with `getConfig()`/`GlobalVarConfig` in `SpecialBrowseData`; remove `FunctionConfigUsage` PHPCS exclude [`98a7d4e`](https://github.com/SemanticMediaWiki/SemanticDrilldown/commit/98a7d4e) ([#139](https://github.com/SemanticMediaWiki/SemanticDrilldown/issues/139))
 

includes/Filter.php

@@ -39,7 +39,9 @@ public function __construct(
 		$this->name = $name;
 		$this->property = $property;
 		$this->category = $category;
-		$this->requiredFilters = $requiredFilters ?? [];
+		$this->requiredFilters = is_array( $requiredFilters )
+			? $requiredFilters
+			: ( $requiredFilters !== null ? [ $requiredFilters ] : [] );
 		$this->int = $int;
 		$this->propertyType = $propertyType;
 		$this->timePeriod = $timePeriod;

tests/phpunit/Unit/FilterTest.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace SD\Tests\Unit;
+
+use PHPUnit\Framework\TestCase;
+use SD\DbService;
+use SD\Filter;
+
+/**
+ * @covers \SD\Filter
+ */
+class FilterTest extends TestCase {
+
+	private function makeFilter( $requiredFilters ): Filter {
+		$db = $this->createMock( DbService::class );
+		return new Filter( $db, 'TestFilter', 'TestProperty', null, $requiredFilters, null );
+	}
+
+	public function testRequiredFiltersReturnsEmptyArrayWhenNull(): void {
+		$filter = $this->makeFilter( null );
+
+		$this->assertSame( [], $filter->requiredFilters() );
+	}
+
+	public function testRequiredFiltersReturnsArrayWhenPassedArray(): void {
+		$filter = $this->makeFilter( [ 'Country' ] );
+
+		$this->assertSame( [ 'Country' ], $filter->requiredFilters() );
+	}
+
+	public function testRequiredFiltersReturnsArrayWhenPassedString(): void {
+		$filter = $this->makeFilter( 'Country' );
+
+		$this->assertSame( [ 'Country' ], $filter->requiredFilters() );
+	}
+
+	public function testRequiredFiltersStringIsIterableAndMatchesFilterName(): void {
+		$filter = $this->makeFilter( 'Country' );
+
+		$found = false;
+		foreach ( $filter->requiredFilters() as $required ) {
+			if ( $required === 'Country' ) {
+				$found = true;
+			}
+		}
+
+		$this->assertTrue( $found, 'Expected to find "Country" in requiredFilters(), not single characters' );
+	}
+
+}