Doesn't work in ro directories

I'm doing some sandboxing/isolation tooling, and I've just hit an issue where even when the environment did not change at all, `nix-direnv` fails when the directory is RO due to: https://github.com/nix-community/nix-direnv/blob/8e58e00a8d71f773f1d389414c57f48ef15c33a7/direnvrc#L100 Is this some hard requirement with reasons I missed or an implementation detail that could be improved? I'm thinking about avoiding re-writting that file if identical already to what it should be.