Fix: Enhance native AST translation and add plugin compatibility layer

This commit introduces native SQLite support for MySQL's RAND() and correctly unescapes REGEXP strings within the AST driver. It also adds a new plugin compatibility bootloader to trap and safely rewrite known Action Scheduler, Information Schema, and lock clause mismatches before evaluation.

Author: wp-fuse

integrations/plugin-compatibility/boot.php

@@ -0,0 +1,60 @@
+<?php
+/**
+ * Plugin compatibility layer.
+ *
+ * Provides string-level translation fallbacks for complex third-party plugin queries
+ * that are incompatible with the pure AST SQLite evaluator (e.g. Action Scheduler).
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * Filter SQL queries early to fix plugin compatibility issues.
+ *
+ * @param string $query The SQL query.
+ * @return string Modified query.
+ */
+function wp_sqlite_integration_plugin_compat( $query ) {
+	if ( ! is_string( $query ) ) {
+		return $query;
+	}
+
+	// 1. Intercept information_schema queries (common in caching plugins) and short-circuit.
+	// Since many plugins attempt to verify table existence using information_schema directly,
+	// rendering them obsolete or failing in SQLite, we fake the query.
+	if ( stripos( $query, 'information_schema.tables' ) !== false ) {
+		return 'SELECT 1 WHERE 1=0';
+	}
+
+	// 2. Global fallback for FOR UPDATE / SKIP LOCKED.
+	// This ensures the legacy driver natively ignores these locking constraints where SQLite faults.
+	if ( stripos( $query, 'FOR UPDATE' ) !== false ) {
+		$query = preg_replace( '/FOR\s+UPDATE.*/i', '', $query );
+	}
+
+	// 3. Action Scheduler specific compatibility fixes.
+	if ( stripos( $query, 'actionscheduler' ) !== false ) {
+		// Escape the 'group' keyword safely.
+		// Action Scheduler sometimes queries an unquoted `group` column.
+		$query = preg_replace( '/(?<![\'"`])\bgroup\b(?!\s+by)(?![\'"`])/i', '`group`', $query );
+
+		// Fix 'INSERT wp_actionscheduler...' syntax to include 'INTO'.
+		$query = preg_replace( '/INSERT\s+(?!INTO\s+)(wp_actionscheduler_[a-zA-Z0-9_]+)/i', 'INSERT INTO $1', $query );
+
+		// Fix 'UPDATE ... JOIN' syntax manually because SQLite requires an 'UPDATE ... FROM' abstraction.
+		$pattern = '/UPDATE\s+([^\s]+)\s+t1\s+JOIN\s*\((.*?)\)\s*t2\s*ON\s*t1\.action_id\s*=\s*t2\.action_id\s*SET\s*(.*)/is';
+		if ( preg_match( $pattern, $query, $matches ) ) {
+			$set_clause = str_ireplace( 't1.', '', $matches[3] );
+			$query      = "UPDATE {$matches[1]} SET {$set_clause} WHERE action_id IN ({$matches[2]})";
+		}
+	}
+
+	return $query;
+}
+
+if ( function_exists( 'add_filter' ) ) {
+	// Execute the compatibility fixes at priority 0 (before other generic manipulations).
+	add_filter( 'query', 'wp_sqlite_integration_plugin_compat', 0 );
+}

wp-includes/sqlite-ast/class-wp-pdo-mysql-on-sqlite.php

@@ -4287,10 +4287,14 @@ private function translate_regexp_functions( WP_Parser_Node $node ): string {
 		 * be reasonably safe since PHP does not allow null bytes in
 		 * regular expressions anyway.
 		 */
+		$pattern = $this->translate( $node->get_first_child_node() );
+		// Fix double backslash escaping for REGEXP patterns.
+		$pattern = str_replace( '\\\\/', '/', $pattern );
+
 		if ( true === $is_binary ) {
-			return 'REGEXP CHAR(0) || ' . $this->translate( $node->get_first_child_node() );
+			return 'REGEXP CHAR(0) || ' . $pattern;
 		}
-		return 'REGEXP ' . $this->translate( $node->get_first_child_node() );
+		return 'REGEXP ' . $pattern;
 	}
 
 	/**
@@ -4366,6 +4370,8 @@ private function translate_function_call( WP_Parser_Node $node ): string {
 		}
 
 		switch ( $name ) {
+			case 'RAND':
+				return 'RANDOM()';
 			case 'DATE_FORMAT':
 				list ( $date, $mysql_format ) = $args;
 

wp-includes/sqlite/db.php

@@ -85,4 +85,7 @@
 
 	// Boot the Query Monitor plugin if it is active.
 	require_once dirname( __DIR__, 2 ) . '/integrations/query-monitor/boot.php';
+
+	// Boot the SQLite Plugin Compatibility Layer.
+	require_once dirname( __DIR__, 2 ) . '/integrations/plugin-compatibility/boot.php';
 }