fix: properly lex imports in OPL

internal/schema/.snapshots/TestLexer-suite=snapshots-import_statement.json

@@ -0,0 +1,13 @@
+[
+  "'import'",
+  "{",
+  "'Foo'",
+  ",",
+  "'Bar'",
+  ",",
+  "'Baz'",
+  "}",
+  "'from'",
+  "'@ory/keto-...'",
+  "EOF"
+]

internal/schema/lexer.go

@@ -307,9 +307,16 @@ func lexBlockComment(l *lexer) stateFn {
 func lexStringLiteral(l *lexer) stateFn {
 	r := l.next()
 	l.ignore()
-	l.acceptRun(digits + letters)
-	if l.peek() != r {
-		return l.errorf("unclosed string literal")
+
+loop:
+	for {
+		switch l.next() {
+		case eof:
+			return l.errorf("unclosed string literal")
+		case r:
+			l.backup()
+			break loop
+		}
 	}
 	l.emit(itemStringLiteral)
 	l.next()

internal/schema/lexer_test.go

@@ -11,10 +11,12 @@ var lexingErrorTestCases = []struct{ name, input string }{
 	{"open comment", "/*"},
 	{"open string literal", "'"},
 	{"non-token", "ü"},
+	{"mixed quotes", `"invalid_literal'`},
 }
 
 var lexableTestCases = []struct{ name, input string }{
 	{"empty", ""},
+	{"import statement", "import { Foo, Bar, Baz } from '@ory/keto-namespace-types'"},
 	{"single class", `
 class name implements Namespace {
 	metadata = {
@@ -117,7 +119,6 @@ func TestLexer(t *testing.T) {
 					}
 					if item.Typ == itemEOF {
 						t.Fatal("reached EOF, but expected error")
-						break
 					}
 				}
 				l.next()

internal/schema/parser_test.go

@@ -17,6 +17,8 @@ var parserTestCases = []struct {
 	name, input string
 }{
 	{"full example", `
+  import { Namespace, SubjectSet, FooBar, Anything } from '@ory/keto-namespace-types'
+
   class User implements Namespace {
 	related: {
 	  manager: User[]