fix(fe): allow commas after interface methods in .d.ts files

Author: strager

docs/CHANGELOG.md

@@ -27,6 +27,8 @@ Semantic Versioning.
   attribute; write 'className' instead"), are now only reported when 'react' is
   imported and if 'preact' is not imported. This fixes false warnings in Preact
   code. ([#1152][])
+* Commas are now allowed after methods in interfaces in `.d.ts` files. (They
+  were previously only allowed in `.ts` files.) ([#1171][])
 
 ## 3.0.0 (2024-01-01)
 
@@ -1385,6 +1387,7 @@ Beta release.
 [wagner riffel]: https://github.com/wgrr
 
 [#1152]: https://github.com/quick-lint/quick-lint-js/issues/1152
+[#1171]: https://github.com/quick-lint/quick-lint-js/issues/1171
 
 [E0001]: https://quick-lint-js.com/errors/E0001/
 [E0003]: https://quick-lint-js.com/errors/E0003/

src/quick-lint-js/fe/parse-class.cpp

@@ -888,20 +888,20 @@ void Parser::parse_and_visit_class_or_interface_member(
             .is_interface_method = is_interface,
         };
         bool is_abstract_method = this->find_modifier(Token_Type::kw_abstract);
-        if (declare_keyword.has_value() ||
-            p->options_.typescript_definition_file) {
+        if (is_interface) {
+          v.visit_enter_function_scope();
+          p->parse_and_visit_interface_function_parameters_and_body_no_scope(
+              v, property_name_span, attributes, param_options);
+          v.visit_exit_function_scope();
+        } else if (declare_keyword.has_value() ||
+                   p->options_.typescript_definition_file) {
           p->parse_and_visit_declare_class_method_parameters_and_body(
               v, property_name_span, attributes, param_options);
         } else if (is_abstract_method) {
           v.visit_enter_function_scope();
           p->parse_and_visit_abstract_function_parameters_and_body_no_scope(
               v, property_name_span, attributes, param_options);
           v.visit_exit_function_scope();
-        } else if (is_interface) {
-          v.visit_enter_function_scope();
-          p->parse_and_visit_interface_function_parameters_and_body_no_scope(
-              v, property_name_span, attributes, param_options);
-          v.visit_exit_function_scope();
         } else {
           // class C { myMethod() {} }
           bool is_possibly_typescript_overload = false;

test/test-parse-typescript-declare-interface.cpp

@@ -60,6 +60,27 @@ TEST_F(Test_Parse_TypeScript_Declare_Interface,
                 ElementsAreArray({interface_decl(u8"I"_sv)}));
   }
 }
+
+TEST_F(Test_Parse_TypeScript_Declare_Interface,
+       commas_are_allowed_between_properties) {
+  {
+    Spy_Visitor p = test_parse_and_visit_module(
+        u8"declare interface I { m(), M(): T, p, P: T, }"_sv, no_diags,
+        typescript_options);
+    EXPECT_THAT(p.property_declarations,
+                ElementsAreArray({u8"m"_sv, u8"M"_sv, u8"p"_sv, u8"P"_sv}));
+  }
+
+  {
+    // NOTE(strager): This used to report that ',' was not allowed only in .d.ts
+    // files. https://github.com/quick-lint/quick-lint-js/issues/1171
+    Spy_Visitor p = test_parse_and_visit_module(
+        u8"declare interface I { m(), M(): T, p, P: T, }"_sv, no_diags,
+        typescript_definition_options);
+    EXPECT_THAT(p.property_declarations,
+                ElementsAreArray({u8"m"_sv, u8"M"_sv, u8"p"_sv, u8"P"_sv}));
+  }
+}
 }
 }