Hi 👋,

I'm working on a feature to add linting in Grape by adding Rack::Lint in the stack. It works well but I'm encountering a Rack::Lint::LintError: Response body is already closed when a Grape API is mounted in a Rails app.

When calling it, Rails's middlewares stack will deal with a Rack::Lint::Wrapper body instead of the real one. This ain't the issue but if we look at Rack::Etag, it might call body.to_ary. Indeed, the to_ary function will be the one in Rack::Lint::Wrapper and it will close the body. Unfortunately, when calling each on it, it will raise a Rack::Lint::LintError even though our original linting was valid.

I've looked into Rack::Lint and somehow, it was setting @closed = false when calling each in Rack 2, but this is not the case anymore.

I've open an issue on our side if you want to take a look at my example.

Thanks!