Add lazy native parser node facade

When a native parser is in use, expose query results through a node
class that defers child materialization until callers actually walk the
tree. The base WP_Parser_Node::$children visibility is loosened to
protected so the facade can populate it on demand.

Author: adamziel

packages/mysql-on-sqlite/src/mysql/native/class-wp-mysql-native-parser-node.php

@@ -11,15 +11,16 @@
  * children are never materialized into PHP arrays unless something actually
  * asks for them.
  *
- * Read methods eagerly call `materialize_native_children()` — once the
- * children have been copied into PHP, `was_mutated()` returns true and the
- * call falls through to the parent implementation. The `was_mutated` flag is
- * NOT a runtime check for whether the native extension is loaded — if this
- * class is in use, the extension is loaded by definition. It tracks whether
- * THIS specific node has had its children pulled into the inherited
- * `$children` array (which happens on first read or first mutation via
- * `append_child()` / `merge_fragment()`). From that point on, the node is a
- * plain PHP-backed `WP_Parser_Node`.
+ * The hedge in those methods (`if ( $this->has_unmaterialized_native_ast() )`)
+ * is NOT a runtime check for whether the native extension is loaded — if this
+ * class is in use, the extension is loaded by definition. It checks whether
+ * THIS specific node still has an authoritative native AST behind it. A node
+ * loses its native backing the first time it is mutated from PHP via
+ * `append_child()` or `merge_fragment()`: those overrides call
+ * `materialize_native_children()`, which copies the native children into the
+ * inherited `$children` array and then drops the native AST reference. From
+ * that point on, the node is a plain PHP-backed `WP_Parser_Node` and the read
+ * methods fall through to the parent implementation.
  *
  * Mutation from PHP is real and intentional — query rewriters in
  * `WP_PDO_MySQL_On_SQLite` (e.g. building synthetic `count(*)` expressions)
@@ -30,7 +31,6 @@
 class WP_MySQL_Native_Parser_Node extends WP_Parser_Node {
 	private $native_ast        = null;
 	private $native_node_index = null;
-	private $was_mutated       = false;
 
 	public function __construct( $rule_id, $rule_name, $native_ast = null, $native_node_index = null ) {
 		parent::__construct( $rule_id, $rule_name );
@@ -67,113 +67,145 @@ public function merge_fragment( $node ) {
 
 	/** @inheritDoc */
 	public function has_child(): bool {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_has_child( $this->native_ast, $this->native_node_index );
+		}
 		return parent::has_child();
 	}
 
 	/** @inheritDoc */
 	public function has_child_node( ?string $rule_name = null ): bool {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_has_child_node( $this->native_ast, $this->native_node_index, $rule_name );
+		}
 		return parent::has_child_node( $rule_name );
 	}
 
 	/** @inheritDoc */
 	public function has_child_token( ?int $token_id = null ): bool {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_has_child_token( $this->native_ast, $this->native_node_index, $token_id );
+		}
 		return parent::has_child_token( $token_id );
 	}
 
 	/** @inheritDoc */
 	public function get_first_child() {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_first_child( $this->native_ast, $this->native_node_index );
+		}
 		return parent::get_first_child();
 	}
 
 	/** @inheritDoc */
 	public function get_first_child_node( ?string $rule_name = null ): ?WP_Parser_Node {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_first_child_node( $this->native_ast, $this->native_node_index, $rule_name );
+		}
 		return parent::get_first_child_node( $rule_name );
 	}
 
 	/** @inheritDoc */
 	public function get_first_child_token( ?int $token_id = null ): ?WP_Parser_Token {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_first_child_token( $this->native_ast, $this->native_node_index, $token_id );
+		}
 		return parent::get_first_child_token( $token_id );
 	}
 
 	/** @inheritDoc */
 	public function get_first_descendant_node( ?string $rule_name = null ): ?WP_Parser_Node {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_first_descendant_node( $this->native_ast, $this->native_node_index, $rule_name );
+		}
 		return parent::get_first_descendant_node( $rule_name );
 	}
 
 	/** @inheritDoc */
 	public function get_first_descendant_token( ?int $token_id = null ): ?WP_Parser_Token {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_first_descendant_token( $this->native_ast, $this->native_node_index, $token_id );
+		}
 		return parent::get_first_descendant_token( $token_id );
 	}
 
 	/** @inheritDoc */
 	public function get_children(): array {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_children( $this->native_ast, $this->native_node_index );
+		}
 		return parent::get_children();
 	}
 
 	/** @inheritDoc */
 	public function get_child_nodes( ?string $rule_name = null ): array {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_child_nodes( $this->native_ast, $this->native_node_index, $rule_name );
+		}
 		return parent::get_child_nodes( $rule_name );
 	}
 
 	/** @inheritDoc */
 	public function get_child_tokens( ?int $token_id = null ): array {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_child_tokens( $this->native_ast, $this->native_node_index, $token_id );
+		}
 		return parent::get_child_tokens( $token_id );
 	}
 
 	/** @inheritDoc */
 	public function get_descendants(): array {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_descendants( $this->native_ast, $this->native_node_index );
+		}
 		return parent::get_descendants();
 	}
 
 	/** @inheritDoc */
 	public function get_descendant_nodes( ?string $rule_name = null ): array {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_descendant_nodes( $this->native_ast, $this->native_node_index, $rule_name );
+		}
 		return parent::get_descendant_nodes( $rule_name );
 	}
 
 	/** @inheritDoc */
 	public function get_descendant_tokens( ?int $token_id = null ): array {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_descendant_tokens( $this->native_ast, $this->native_node_index, $token_id );
+		}
 		return parent::get_descendant_tokens( $token_id );
 	}
 
 	/** @inheritDoc */
 	public function get_start(): int {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_start( $this->native_ast, $this->native_node_index );
+		}
 		return parent::get_start();
 	}
 
 	/** @inheritDoc */
 	public function get_length(): int {
-		$this->materialize_native_children();
+		if ( $this->has_unmaterialized_native_ast() ) {
+			return wp_sqlite_mysql_native_ast_get_length( $this->native_ast, $this->native_node_index );
+		}
 		return parent::get_length();
 	}
 
 	/**
-	 * Indicates whether this node has been mutated from PHP.
+	 * Indicates whether this node still has an unmaterialized native AST.
 	 *
-	 * Returns false for freshly-parsed nodes whose children still live in the
-	 * Rust-owned AST buffer; returns true once `append_child()` or
-	 * `merge_fragment()` has copied the children into the inherited
-	 * `$children` array and dropped the native AST reference.
+	 * Returns true for freshly-parsed nodes whose children live in the
+	 * Rust-owned AST buffer; returns false once the node has been mutated and
+	 * its children copied into the inherited `$children` array (see
+	 * self::materialize_native_children()).
 	 *
 	 * This is a per-instance state check, not a check for whether the native
 	 * extension is loaded.
 	 */
-	private function was_mutated(): bool {
-		return $this->was_mutated;
+	private function has_unmaterialized_native_ast(): bool {
+		return null !== $this->native_ast;
 	}
 
 	/**
@@ -182,17 +214,16 @@ private function was_mutated(): bool {
 	 *
 	 * Called before any mutation (append_child, merge_fragment) so the node's
 	 * authoritative state lives in PHP from that point on. After this runs,
-	 * was_mutated() returns true and read methods fall through to the parent
-	 * WP_Parser_Node implementation.
+	 * has_unmaterialized_native_ast() returns false and read methods fall
+	 * through to the parent WP_Parser_Node implementation.
 	 */
 	private function materialize_native_children(): void {
-		if ( $this->was_mutated ) {
+		if ( ! $this->has_unmaterialized_native_ast() ) {
 			return;
 		}
 
 		$this->children          = wp_sqlite_mysql_native_ast_get_children( $this->native_ast, $this->native_node_index );
 		$this->native_ast        = null;
 		$this->native_node_index = null;
-		$this->was_mutated       = true;
 	}
 }