DB/DirectDatabaseQuery: bug fix - ignore TRUNCATE queries

Prevent unsolvable false positives for `TRUNCATE` queries. Those cannot be cached and need a direct DB query. (second opinion appreciated!)

Includes unit tests.

Fixes 1947

WordPress/Sniffs/DB/DirectDatabaseQuerySniff.php

@@ -12,6 +12,7 @@
 use PHP_CodeSniffer\Util\Tokens;
 use PHPCSUtils\Tokens\Collections;
 use PHPCSUtils\Utils\Conditions;
+use PHPCSUtils\Utils\TextStrings;
 use WordPressCS\WordPress\Helpers\RulesetPropertyHelper;
 use WordPressCS\WordPress\Sniff;
 
@@ -194,13 +195,18 @@ public function process_token( $stackPtr ) {
 
 		$endOfStatement = $this->phpcsFile->findNext( array( \T_SEMICOLON, \T_CLOSE_TAG ), ( $stackPtr + 1 ) );
 
-		// Check for Database Schema Changes.
+		// Check for Database Schema Changes/ table truncation.
 		for ( $_pos = ( $stackPtr + 1 ); $_pos < $endOfStatement; $_pos++ ) {
 			$_pos = $this->phpcsFile->findNext( Tokens::$textStringTokens, $_pos, $endOfStatement );
 			if ( false === $_pos ) {
 				break;
 			}
 
+			if ( strpos( TextStrings::stripQuotes( $this->tokens[ $_pos ]['content'] ), 'TRUNCATE ' ) === 0 ) {
+				// Ignore queries to truncate the database as caching those is irrelevant and they need a direct db query.
+				return;
+			}
+
 			if ( preg_match( '#\b(?:ALTER|CREATE|DROP)\b#i', $this->tokens[ $_pos ]['content'] ) > 0 ) {
 				$this->phpcsFile->addWarning( 'Attempting a database schema change is discouraged.', $_pos, 'SchemaChange' );
 			}

WordPress/Tests/DB/DirectDatabaseQueryUnitTest.inc

@@ -307,3 +307,13 @@ function correctly_determine_end_of_statement() {
 	<?php
 	$next_query = 'ALTER TABLE TO ADD SOME FIELDS' ); // Should not be flagged as not in a call to $wpdb.
 }
+
+function stay_silent_for_truncate_query() {
+	global $wpdb;
+	$wpdb->query(
+		$wpdb->prepare(
+			'TRUNCATE TABLE `%1$s`',
+			plugin_get_table_name( 'Name' )
+		)
+	);
+}