Add support for CURRENT_TIMESTAMP() calls with parentheses (#151)

While SQLite does support `CURRENT_TIMESTAMP` function calls natively,
it doesn't support calling the function with parentheses in the form of
`CURRENT_TIMESTAMP()`.

This pull request removes the parentheses after `CURRENT_TIMESTAMP`
keyword for all types of queries.

The following types of queries will now work:

```sql
SELECT
    current_timestamp AS t1,
    CURRENT_TIMESTAMP AS t2,
    current_timestamp() AS t3,
    CURRENT_TIMESTAMP() AS t4;

INSERT INTO _dates (option_name, option_value) VALUES ('first', current_timestamp());

UPDATE _dates SET option_value = CURRENT_TIMESTAMP();

DELETE FROM _dates WHERE option_value = CURRENT_TIMESTAMP();
```

Closes
#129.

---------

Co-authored-by: Bero <[email protected]>

Author: JanJakes

tests/WP_SQLite_Translator_Tests.php

@@ -3008,6 +3008,46 @@ public function testDefaultNullValue() {
 		);
 	}
 
+	public function testCurrentTimestamp() {
+		// SELECT
+		$results = $this->assertQuery(
+			'SELECT
+				current_timestamp AS t1,
+				CURRENT_TIMESTAMP AS t2,
+				current_timestamp() AS t3,
+				CURRENT_TIMESTAMP() AS t4'
+		);
+		$this->assertIsArray( $results );
+		$this->assertCount( 1, $results );
+		$this->assertRegExp( '/\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d/', $results[0]->t1 );
+		$this->assertRegExp( '/\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d/', $results[0]->t2 );
+		$this->assertRegExp( '/\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d/', $results[0]->t3 );
+
+		// INSERT
+		$this->assertQuery(
+			"INSERT INTO _dates (option_name, option_value) VALUES ('first', CURRENT_TIMESTAMP())"
+		);
+		$results = $this->assertQuery( 'SELECT option_value AS t FROM _dates' );
+		$this->assertCount( 1, $results );
+		$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' );
+		$results = $this->assertQuery( 'SELECT option_value AS t FROM _dates' );
+		$this->assertCount( 1, $results );
+		$this->assertEmpty( $results[0]->t );
+
+		$this->assertQuery( 'UPDATE _dates SET option_value = CURRENT_TIMESTAMP()' );
+		$results = $this->assertQuery( 'SELECT option_value AS t FROM _dates' );
+		$this->assertCount( 1, $results );
+		$this->assertRegExp( '/\d\d\d\d-\d\d-\d\d \d\d:\d\d:\d\d/', $results[0]->t );
+
+		// DELETE
+		// We can only assert that the query passes. It is not guaranteed that we'll actually
+		// delete the existing record, as the delete query could fall into a different second.
+		$this->assertQuery( 'DELETE FROM _dates WHERE option_value = CURRENT_TIMESTAMP()' );
+	}
+
 	/**
 	 * @dataProvider mysqlVariablesToTest
 	 */

wp-includes/sqlite/class-wp-sqlite-translator.php

@@ -772,7 +772,23 @@ public function get_return_value() {
 	 * @throws Exception If the query is not supported.
 	 */
 	private function execute_mysql_query( $query ) {
-		$tokens           = ( new WP_SQLite_Lexer( $query ) )->tokens;
+		$tokens = ( new WP_SQLite_Lexer( $query ) )->tokens;
+
+		// SQLite does not support CURRENT_TIMESTAMP() calls with parentheses.
+		// Since CURRENT_TIMESTAMP() can appear in most types of SQL queries,
+		// let's remove the parentheses globally before further processing.
+		foreach ( $tokens as $i => $token ) {
+			if ( WP_SQLite_Token::TYPE_KEYWORD === $token->type && 'CURRENT_TIMESTAMP' === $token->keyword ) {
+				$paren_open  = $tokens[ $i + 1 ] ?? null;
+				$paren_close = $tokens[ $i + 2 ] ?? null;
+				if ( WP_SQLite_Token::TYPE_OPERATOR === $paren_open->type && '(' === $paren_open->value
+					&& WP_SQLite_Token::TYPE_OPERATOR === $paren_close->type && ')' === $paren_close->value ) {
+					unset( $tokens[ $i + 1 ], $tokens[ $i + 2 ] );
+				}
+			}
+		}
+		$tokens = array_values( $tokens );
+
 		$this->rewriter   = new WP_SQLite_Query_Rewriter( $tokens );
 		$this->query_type = $this->rewriter->peek()->value;