[mofr]

Stacked on #343; retargets to v34 once #343 merges.

An exception handler is a method marked with @winter.web.exception_handler. Its first argument is annotated with the exceptions it handles (a union for several):

class FileStorageExceptionHandlers:
    @winter.web.exception_handler
    @winter.web.response_status(HTTPStatus.BAD_GATEWAY)
    def handle_download(self, exception: FileStorageDownloadException) -> ErrorDTO:
        ...

• create_urls(app) and generate_openapi(app) collect the handlers of the application from app.definitions (handler methods and @problem exceptions), over the built-in handlers of winter.web (500 for Exception, redirect, Winter's own problems). A handler of the application replaces the built-in one of the same exception class; then the handler of the nearest class in the exception's MRO handles it.
• Two handlers of one exception class in an application, or a handler whose first argument is not annotated with exceptions, fail on startup.
• Every handler handles its exceptions in all endpoints of its application. @raises(Exc) only declares the response for OpenAPI.
• Removed: ExceptionHandler, exception_handlers_registry (add_handler, set_default_handler), the handler argument of @raises.
• The isolation test tests/test_application_scope.py passes; xfail is removed.
• OpenAPI: @raises(X) for an exception without a handler now documents the built-in 500 response; before, the default handler's response overwrote the success response.

🤖 Generated with Claude Code