Add support for CURRENT_TIMESTAMP() and NOW()

Author: JanJakes

tests/WP_SQLite_Driver_Tests.php

@@ -3404,7 +3404,7 @@ public function testCurrentTimestamp() {
 		$this->assertRegExp( '/\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d/', $results[0]->t );
 
 		// UPDATE
-		$this->assertQuery( 'UPDATE _dates SET option_value = NULL' );
+		$this->assertQuery( "UPDATE _dates SET option_value = ''" );
 		$results = $this->assertQuery( 'SELECT option_value AS t FROM _dates' );
 		$this->assertCount( 1, $results );
 		$this->assertEmpty( $results[0]->t );

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

@@ -1586,6 +1586,14 @@ private function translate_runtime_function_call( WP_Parser_Node $node ): string
 		}
 
 		switch ( $child->id ) {
+			case WP_MySQL_Lexer::CURRENT_TIMESTAMP_SYMBOL:
+			case WP_MySQL_Lexer::NOW_SYMBOL:
+				/*
+				 * 1) SQLite doesn't support CURRENT_TIMESTAMP() with parentheses.
+				 * 2) In MySQL, CURRENT_TIMESTAMP and CURRENT_TIMESTAMP() are an
+				 *    alias of NOW(). In SQLite, there is no NOW() function.
+				 */
+				return 'CURRENT_TIMESTAMP';
 			case WP_MySQL_Lexer::DATE_ADD_SYMBOL:
 			case WP_MySQL_Lexer::DATE_SUB_SYMBOL:
 				$nodes = $node->get_child_nodes();