Explicitly support only ASCII identifiers

Author: JanJakes

tests/WP_SQLite_Driver_Tests.php

@@ -5139,4 +5139,29 @@ public function testColumnNamesAreNotCaseSensitive(): void {
 		$this->assertCount( 1, $result );
 		$this->assertSame( 'value', $result[0]->Field );
 	}
+
+	public function testAliasesMustBeAscii(): void {
+		$this->expectException( WP_SQLite_Driver_Exception::class );
+		$this->expectExceptionMessage( 'The SQLite driver only supports ASCII characters in identifiers.' );
+		$this->assertQuery( 'SELECT 123 AS `ńôñ-ášçíì`' );
+	}
+
+	public function testTableNamesMustBeAscii(): void {
+		$this->expectException( WP_SQLite_Driver_Exception::class );
+		$this->expectExceptionMessage( 'The SQLite driver only supports ASCII characters in identifiers.' );
+		$this->assertQuery( 'CREATE TABLE `ńôñ-ášçíì` (id INT)' );
+	}
+
+	public function testColumnNamesMustBeAscii(): void {
+		$this->expectException( WP_SQLite_Driver_Exception::class );
+		$this->expectExceptionMessage( 'The SQLite driver only supports ASCII characters in identifiers.' );
+		$this->assertQuery( 'CREATE TABLE t (`ńôñ-ášçíì` INT)' );
+	}
+
+	public function testIndexNamesMustBeAscii(): void {
+		$this->expectException( WP_SQLite_Driver_Exception::class );
+		$this->expectExceptionMessage( 'The SQLite driver only supports ASCII characters in identifiers.' );
+		$this->assertQuery( 'CREATE TABLE t (id INT)' );
+		$this->assertQuery( 'CREATE INDEX `ńôñ-ášçíì` ON t (id)' );
+	}
 }

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

@@ -2121,7 +2121,21 @@ private function translate( $node ): ?string {
 			case 'identifierKeyword':
 				return '`' . $this->translate( $node->get_first_child() ) . '`';
 			case 'pureIdentifier':
-				return $this->translate_pure_identifier( $node );
+				$value = $this->translate_pure_identifier( $node );
+
+				/*
+				 * At the moment, we only support ASCII bytes in all identifiers.
+				 * This is because SQLite doesn't support case-insensitive Unicode
+				 * character matching: https://sqlite.org/faq.html#q18
+				 */
+				for ( $i = 0; $i < strlen( $value ); $i++ ) {
+					if ( ord( $value[ $i ] ) > 127 ) {
+						throw $this->new_driver_exception(
+							'The SQLite driver only supports ASCII characters in identifiers.'
+						);
+					}
+				}
+				return $value;
 			case 'textStringLiteral':
 				return $this->translate_string_literal( $node );
 			case 'dataType':

wp-includes/sqlite-ast/class-wp-sqlite-information-schema-builder.php

@@ -2113,6 +2113,19 @@ private function get_value( WP_Parser_Node $node ): string {
 		foreach ( $node->get_children() as $child ) {
 			if ( $child instanceof WP_Parser_Node ) {
 				$value = $this->get_value( $child );
+
+				/*
+				 * At the moment, we only support ASCII bytes in all identifiers.
+				 * This is because SQLite doesn't support case-insensitive Unicode
+				 * character matching: https://sqlite.org/faq.html#q18
+				 */
+				if ( 'pureIdentifier' === $child->rule_name ) {
+					for ( $i = 0; $i < strlen( $value ); $i++ ) {
+						if ( ord( $value[ $i ] ) > 127 ) {
+							throw new Exception( 'The SQLite driver only supports ASCII characters in identifiers.' );
+						}
+					}
+				}
 			} else {
 				$value = $child->get_value();
 			}