Fix wp_using_ext_object_cache() return type and add early-load guard.

Author: liaisontw

src/wp-includes/load.php

@@ -808,20 +808,21 @@ function wp_set_wpdb_vars() {
  * @return bool The current 'using' setting.
  */
 function wp_using_ext_object_cache( $using = null ) {
-    global $_wp_using_ext_object_cache;
+	global $_wp_using_ext_object_cache;
 
-    // Save the current state to return later.
-    $current_using = $_wp_using_ext_object_cache;
+	// Save the current state to return later.
+	$current_using = $_wp_using_ext_object_cache;
 
-    if ( null !== $using ) {
-        $_wp_using_ext_object_cache = (bool) $using;
-    }
+	if ( null !== $using ) {
+		$_wp_using_ext_object_cache = (bool) $using;
+	}
+
+	if ( null === $_wp_using_ext_object_cache ) {
+		// If the global is uninitialized, the value would be null, which violates the type signature.
+		return false;
+	}
 
-    /**
-     * Ensure the returned value is always a boolean. 
-     * If the global is uninitialized, it could be null, which violates the type signature.
-     */
-    return (bool) $current_using;
+	return (bool) $current_using;
 }
 
 /**

tests/phpunit/tests/load/wpUsingExtObjectCache.php

@@ -0,0 +1,72 @@
+<?php
+
+/**
+ * Tests for wp_using_ext_object_cache().
+ *
+ * @group load
+ *
+ * @covers ::wp_using_ext_object_cache
+ */
+class Tests_Load_wpUsingExtObjectCache extends WP_UnitTestCase {
+
+	/**
+	 * Resets the global variable before each test to ensure isolation.
+	 */
+	public function set_up() {
+		parent::set_up();
+		global $_wp_using_ext_object_cache;
+		$_wp_using_ext_object_cache = null;
+	}
+
+	/**
+	 * Tests the toggling and retrieval of the external object cache state.
+	 *
+	 * @ticket  #64950 wp_using_ext_object_cache can return null
+	 *
+	 * @dataProvider data_wp_using_ext_object_cache
+	 *
+	 * @param mixed $initial_global  The initial value of the global variable.
+	 * @param mixed $input_param     The value passed to the function.
+	 * @param bool  $expected_return The expected return value (previous state).
+	 * @param bool  $final_global    The expected state of the global after execution.
+	 */
+	public function test_wp_using_ext_object_cache( $initial_global, $input_param, $expected_return, $final_global ) {
+		global $_wp_using_ext_object_cache;
+
+		// Set the environment to the initial state.
+		$_wp_using_ext_object_cache = $initial_global;
+
+		// Verify the function return value matches the expected previous state.
+		$this->assertSame( $expected_return, wp_using_ext_object_cache( $input_param ) );
+
+		// Verify the global variable has been updated to the new state.
+		$this->assertSame( $final_global, $_wp_using_ext_object_cache );
+	}
+
+	/**
+	 * Data provider for test_wp_using_ext_object_cache().
+	 *
+	 * Format: array( Initial Global, Function Input, Expected Return, Expected Final Global )
+	 *
+	 * @return array
+	 */
+	public function data_wp_using_ext_object_cache() {
+		return array(
+			// Scenario 1: Read current state without changing it.
+			array( true, null, true, true ),
+			array( false, null, false, false ),
+
+			// Scenario 2: Handle uninitialized global state.
+			array( null, null, false, null ),
+
+			// Scenario 3: Change state and return the previous value.
+			array( false, true, false, true ),
+			array( true, false, true, false ),
+
+			// Scenario 4: Ensure type casting to boolean.
+			array( false, 1, false, true ),  // Integer 1 becomes true.
+			array( true, 0, true, false ), // Integer 0 becomes false.
+			array( false, '1', false, true ),  // String '1' becomes true.
+		);
+	}
+}