How do you do encapsulation without an mli? can you hide the type implementation to the module user? can you ensure the exported functions (which are all of them without an mli) maintain your type invariant?
> the real problém is that the documentation is often worse too, as the .mli is autogenerated and documented afterwards
Of course, that would defeat the purpose of having interfaces and is incredibly bad practice. People do that when they try to fix an already broken codebase. It's actually pretty ironic that people who care about type safety (which I is why they use OCaml in the first place) don't value (or understand) things like encapsulation.
I find Rust is really effective in this regard. From my understanding of the capabilities of mli files, Rust's visibility modifiers are even more powerful in terms of effectively hiding implementation details and maintaining invariants, but they're all written inline in the source code (with the `pub` keyword).
I agree that the encapsulation capabilities of mli files are great, but I don't see why they need to be written in a separate file (apart from the obvious reason: that's how OCaml does it, and you can't just change a language's design just because you don't like one bit of it!)
> the real problém is that the documentation is often worse too, as the .mli is autogenerated and documented afterwards
Of course, that would defeat the purpose of having interfaces and is incredibly bad practice. People do that when they try to fix an already broken codebase. It's actually pretty ironic that people who care about type safety (which I is why they use OCaml in the first place) don't value (or understand) things like encapsulation.