fix: prevent type errors in Syndication_Logger when no logs exist

When the Syndication_Logger attempts to retrieve logs from post meta or options that don't yet exist, WordPress returns an empty string rather than an empty array. This caused "Array to string conversion" warnings when the code attempted array operations (count, array_slice, array index) on the returned value.

The fix adds defensive type checking after both get_post_meta() and get_option() calls to ensure the log variable is always an array before performing array operations. The get_option() call also now correctly specifies an empty array as its default value instead of boolean true.

Integration tests verify that logging works correctly for posts with no existing logs, posts with existing logs, and that error counts are tracked properly.

Fixes #152

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: GaryJones

includes/class-syndication-logger.php

@@ -305,7 +305,13 @@ private function log( $storage_type, $msg_type, $object_type, $object_id, $statu
 					return new WP_Error( 'logger_no_post', __( 'The post_id provided does not exist.', 'push-syndication' ) );
 				}
 
-				$log = get_post_meta( $post->ID, 'syn_log', true);
+				$log = get_post_meta( $post->ID, 'syn_log', true );
+
+				// When no meta exists, get_post_meta() with $single=true returns ''.
+				// Initialize as empty array for first log entry.
+				if ( '' === $log ) {
+					$log = array();
+				}
 
 				if ( empty( $log ) ) {
 					$log[0] = $log_entry;
@@ -339,9 +345,10 @@ private function log( $storage_type, $msg_type, $object_type, $object_id, $statu
 			}
 
 		} else if ( 'option' == $storage_type ) {
-			// Storing the log in an option value
+			// Storing the log in an option value.
+			// Default to empty array when option doesn't exist.
+			$log = get_option( 'syn_log', array() );
 
-			$log = get_option( 'syn_log', true );
 			if ( empty( $log ) ) {
 				$log[0] = $log_entry;
 			} else {

tests/Integration/LoggerTest.php

@@ -0,0 +1,121 @@
+<?php
+/**
+ * Tests for the Syndication_Logger class.
+ *
+ * @package Automattic\Syndication\Tests
+ */
+
+namespace Syndication\Tests;
+
+use Yoast\WPTestUtils\WPIntegration\TestCase as WPIntegrationTestCase;
+use Syndication_Logger;
+
+/**
+ * Class LoggerTest
+ *
+ * @covers Syndication_Logger
+ */
+class LoggerTest extends WPIntegrationTestCase {
+
+	/**
+	 * Test that logging to a post without existing logs works correctly.
+	 *
+	 * This tests the fix for the "Array to string conversion" error that occurred
+	 * when get_post_meta was called with the third parameter as true, returning
+	 * an empty string instead of an empty array when no meta existed.
+	 *
+	 * Uses log_post_error because log_post_info requires debug_level='info'.
+	 *
+	 * @covers Syndication_Logger::log_post_error
+	 */
+	public function test_log_to_post_without_existing_logs(): void {
+		// Create a site post.
+		$site_id = $this->factory()->post->create(
+			array(
+				'post_type'   => 'syn_site',
+				'post_status' => 'publish',
+			)
+		);
+
+		// Log should work without throwing an error.
+		Syndication_Logger::log_post_error(
+			$site_id,
+			'test_status',
+			'Test message',
+			null,
+			array()
+		);
+
+		// Verify the log was stored.
+		$log = get_post_meta( $site_id, 'syn_log', true );
+		$this->assertIsArray( $log );
+		$this->assertNotEmpty( $log );
+	}
+
+	/**
+	 * Test that logging to a post with existing logs appends correctly.
+	 *
+	 * @covers Syndication_Logger::log_post_error
+	 */
+	public function test_log_to_post_with_existing_logs(): void {
+		$site_id = $this->factory()->post->create(
+			array(
+				'post_type'   => 'syn_site',
+				'post_status' => 'publish',
+			)
+		);
+
+		// Create initial log entry.
+		Syndication_Logger::log_post_error(
+			$site_id,
+			'first_status',
+			'First message',
+			null,
+			array()
+		);
+
+		// Add second log entry.
+		Syndication_Logger::log_post_error(
+			$site_id,
+			'second_status',
+			'Second message',
+			null,
+			array()
+		);
+
+		// Verify both logs exist.
+		$log = get_post_meta( $site_id, 'syn_log', true );
+		$this->assertIsArray( $log );
+		$this->assertCount( 2, $log );
+	}
+
+	/**
+	 * Test that error logging works correctly.
+	 *
+	 * @covers Syndication_Logger::log_post_error
+	 */
+	public function test_log_post_error(): void {
+		$site_id = $this->factory()->post->create(
+			array(
+				'post_type'   => 'syn_site',
+				'post_status' => 'publish',
+			)
+		);
+
+		Syndication_Logger::log_post_error(
+			$site_id,
+			'error_status',
+			'Error message',
+			null,
+			array()
+		);
+
+		$log = get_post_meta( $site_id, 'syn_log', true );
+		$this->assertIsArray( $log );
+		$this->assertNotEmpty( $log );
+
+		// Error count should be tracked.
+		$errors = get_post_meta( $site_id, 'syn_log_errors', true );
+		$this->assertEquals( 1, (int) $errors );
+	}
+}