Enable read usage of information schema tables in write queries

Author: JanJakes

tests/WP_SQLite_Driver_Tests.php

@@ -9622,4 +9622,93 @@ public function testFullyQualifiedTableName(): void {
 		$result = $this->assertQuery( 'SHOW TABLES FROM wp' );
 		$this->assertCount( 0, $result );
 	}
+
+	public function testWriteWithUsageOfInformationSchemaTables(): void {
+		// Ensure "information_schema.tables" is empty.
+		$this->assertQuery( 'DROP TABLE _options, _dates' );
+		$result = $this->assertQuery( 'SELECT * FROM information_schema.tables' );
+		$this->assertCount( 0, $result );
+
+		// Create a table.
+		$this->assertQuery( 'CREATE TABLE t (id INT, value VARCHAR(255))' );
+
+		// INSERT with SELECT from information schema.
+		$this->assertQuery( 'INSERT INTO t (id, value) SELECT 1, table_name FROM information_schema.tables' );
+		$result = $this->assertQuery( 'SELECT * FROM t' );
+		$this->assertCount( 1, $result );
+		$this->assertEquals(
+			array(
+				(object) array(
+					'id'    => '1',
+					'value' => 't',
+				),
+			),
+			$result
+		);
+
+		// INSERT with subselect from information schema.
+		$this->assertQuery( 'INSERT INTO t (id, value) SELECT 2, table_name FROM (SELECT table_name FROM information_schema.tables)' );
+		$result = $this->assertQuery( 'SELECT * FROM t' );
+		$this->assertCount( 2, $result );
+		$this->assertEquals(
+			array(
+				(object) array(
+					'id'    => '1',
+					'value' => 't',
+				),
+				(object) array(
+					'id'    => '2',
+					'value' => 't',
+				),
+			),
+			$result
+		);
+
+		// INSERT with JOIN on information schema.
+		$this->assertQuery(
+			'INSERT INTO t (id, value)
+			SELECT 3, it.table_name
+			FROM information_schema.schemata s
+			JOIN information_schema.tables it ON s.schema_name = it.table_schema'
+		);
+		$result = $this->assertQuery( 'SELECT * FROM t' );
+		$this->assertCount( 3, $result );
+		$this->assertEquals(
+			array(
+				(object) array(
+					'id'    => '1',
+					'value' => 't',
+				),
+				(object) array(
+					'id'    => '2',
+					'value' => 't',
+				),
+				(object) array(
+					'id'    => '3',
+					'value' => 't',
+				),
+			),
+			$result
+		);
+
+		// TODO: UPDATE with JOIN on information schema is not supported yet.
+
+		// DELETE with JOIN on information schema.
+		$this->assertQuery( 'UPDATE t SET value = "other" WHERE id > 1' );
+		$this->assertQuery( 'DELETE t FROM t JOIN information_schema.tables it ON t.value = it.table_name' );
+		$result = $this->assertQuery( 'SELECT * FROM t' );
+		$this->assertEquals(
+			array(
+				(object) array(
+					'id'    => '2',
+					'value' => 'other',
+				),
+				(object) array(
+					'id'    => '3',
+					'value' => 'other',
+				),
+			),
+			$result
+		);
+	}
 }

wp-includes/sqlite-ast/class-wp-sqlite-driver.php

@@ -4083,11 +4083,6 @@ public function translate_select_item( WP_Parser_Node $node ): string {
 	 * @throws WP_SQLite_Driver_Exception When the translation fails.
 	 */
 	public function translate_table_ref( WP_Parser_Node $node ): string {
-		// Information schema is currently accessible only in read-only queries.
-		if ( ! $this->is_readonly ) {
-			return $this->translate_sequence( $node->get_children() );
-		}
-
 		// The table reference is in "<schema>.<table>" or "<table>" format.
 		$parts  = $node->get_descendant_nodes( 'identifier' );
 		$table  = array_pop( $parts );