Tests: Add unit tests for object_ids handling in WP_Term_Query

src/wp-includes/class-wp-term-query.php

@@ -76,7 +76,7 @@ class WP_Term_Query {
 	 * List of terms located by the query.
 	 *
 	 * @since 4.6.0
-	 * @var array
+	 * @var array|null
 	 */
 	public $terms;
 
@@ -590,7 +590,7 @@ public function get_terms() {
 			);
 		}
 
-		if ( '' === $args['object_ids'] ) {
+		if ( empty( $args['object_ids'] ) && ! is_numeric( $args['object_ids'] ) ) {
 			$args['object_ids'] = array();
 		} else {
 			$args['object_ids'] = array_map( 'intval', (array) $args['object_ids'] );

tests/phpunit/tests/term/query.php

@@ -451,6 +451,46 @@ public function test_object_ids_cache_should_be_invalidated_by_term_relationship
 		$this->assertSameSets( array( $terms[1] ), $found );
 	}
 
+	/**
+	 * @ticket 63256
+	 */
+	public function test_object_ids_null_should_return_all_terms() {
+		register_taxonomy( 'wptests_tax_1', 'post' );
+
+		$terms = self::factory()->term->create_many( 3, array( 'taxonomy' => 'wptests_tax_1' ) );
+
+		$query = new WP_Term_Query(
+			array(
+				'taxonomy'   => 'wptests_tax_1',
+				'object_ids' => null,
+				'hide_empty' => false,
+				'fields'     => 'ids',
+			)
+		);
+
+		$this->assertSameSets( $terms, $query->terms, 'When object_ids is null, all terms should be returned without filtering.' );
+	}
+
+	/**
+	 * @ticket 63256
+	 */
+	public function test_object_ids_zero_should_be_treated_as_numeric() {
+		register_taxonomy( 'wptests_tax_1', 'post' );
+
+		self::factory()->term->create( array( 'taxonomy' => 'wptests_tax_1' ) );
+
+		$query = new WP_Term_Query(
+			array(
+				'taxonomy'   => 'wptests_tax_1',
+				'object_ids' => 0,
+				'hide_empty' => false,
+				'fields'     => 'ids',
+			)
+		);
+
+		$this->assertSame( array(), $query->terms, 'When object_ids is 0, it should be treated as a numeric value and return an array.' );
+	}
+
 	/**
 	 * @ticket 38295
 	 * @group cache