Translate SUBSTRING() to SUBSTR(); avoid SUBSTRING() due to lack of support on old SQLite versions

Author: JanJakes

tests/WP_SQLite_Driver_Tests.php

@@ -11231,4 +11231,18 @@ public function testVersionFunction(): void {
 		$result = $this->engine->query( 'SELECT VERSION()' );
 		$this->assertSame( '8.0.38', $result[0]->{'VERSION()'} );
 	}
+
+	public function testSubstringFunction(): void {
+		$result = $this->assertQuery( "SELECT SUBSTRING('abcdef', 1, 3) AS s" );
+		$this->assertSame( 'abc', $result[0]->s );
+
+		$result = $this->assertQuery( "SELECT SUBSTRING('abcdef', 4) AS s" );
+		$this->assertSame( 'def', $result[0]->s );
+
+		$result = $this->assertQuery( "SELECT SUBSTRING('abcdef' FROM 1 FOR 3) AS s" );
+		$this->assertSame( 'abc', $result[0]->s );
+
+		$result = $this->assertQuery( "SELECT SUBSTRING('abcdef' FROM 4) AS s" );
+		$this->assertSame( 'def', $result[0]->s );
+	}
 }

wp-includes/sqlite-ast/class-wp-pdo-mysql-on-sqlite.php

@@ -3496,6 +3496,22 @@ private function translate( $node ): ?string {
 				return $this->translate_runtime_function_call( $node );
 			case 'functionCall':
 				return $this->translate_function_call( $node );
+			case 'substringFunction':
+				$nodes = $node->get_child_nodes();
+				if ( count( $nodes ) === 2 ) {
+					return sprintf(
+						'SUBSTR(%s, %s)',
+						$this->translate( $nodes[0] ),
+						$this->translate( $nodes[1] )
+					);
+				} else {
+					return sprintf(
+						'SUBSTR(%s, %s, %s)',
+						$this->translate( $nodes[0] ),
+						$this->translate( $nodes[1] ),
+						$this->translate( $nodes[2] )
+					);
+				}
 			case 'systemVariable':
 				$var_ident_type = $node->get_first_child_node( 'varIdentType' );
 				$type_token     = $var_ident_type ? $var_ident_type->get_first_child_token() : null;
@@ -4116,7 +4132,7 @@ private function translate_runtime_function_call( WP_Parser_Node $node ): string
 			case WP_MySQL_Lexer::LEFT_SYMBOL:
 				$nodes = $node->get_child_nodes();
 				return sprintf(
-					'SUBSTRING(%s, 1, %s)',
+					'SUBSTR(%s, 1, %s)',
 					$this->translate( $nodes[0] ),
 					$this->translate( $nodes[1] )
 				);