The language however is quite nice and the stdlib is fairly complete.
Edit: Another problem I see is the (over?) reliance on PPX preprocessors. It does make a lot of tasks simpler, but it is too much magic for me personally.
OCaml is an academic language like Haskell. Academics tend to neglect documentation in general, be it because what they're working on is mostly self-serving, lack of time/enthusiasm or a tinge of elitism on that "this should be obvious and if not just read the code".
Rust adherents seem to really want to take over the world and they realize that great documentation is an enabler for that.
Also the standard libraries and compiler set a pretty strong precedent.
It is a complete and up-to-date manual of the entire OCaml distribution, including executables, language, runtime, and standard library. It's rare to find modern industry-driven languages with this level of coherent documentation.
But regarding third-party library documentation, that is indeed spotty. Some people publish it, some don't. I have to reluctantly conclude it's due to a lack of tooling which automates the tedious processes.
Some of it can be driven by external factors: javascript was the only choice for an important domain for a long time.
Some if it I think is due to attractive syntax, or tooling. Python for example, horrible runtime performance, but people were drawn to it for probably syntax and tooling reasons.
Comparing Rust and OCaml:
The OCaml syntax is a bit odd. I was quite taken by F#, which is a very similar language to OCaml, but with some of the cumbersome syntax removed. F# seemed quite nice, looking at OCaml it just felt horrible and I didn't want to deal with it. In practice I know it would be fine, just like you get used to Lisp and it's parens, but there is a real psychology there that turns people away.
OCaml has good runtime performance, but its not the kind of language that will draw in C/C++ programmers or work for domains where you need C or C++ currently. Lack of multi-core is a huge turn off for a lot of people. This is the era where multi-core is our only path to more performance!
Rust syntax is a little more familiar to people, the runtime performance is top notch, very good at leveraging more cores, and maybe most importantly the community has made a concerted effort to make the language as approachable as possible. With good/friendly documentation and community. Easy install process, decent editor support, etc. Go ask a question about "Which way is faster" in a C# forum, you get a lecture about how you shouldn't worry about that. On a Rust forum you get an deep dive into performance concerns and language design. This seems to have drawn in people from communities you wouldn't expect. A low level, complicated language that Ruby and Javascript developers are drawn to? An interesting result!
Tooling? How so? Like the REPL? Because when I think of tooling, I think of things like IDEs, dependency management, and distribution. Python has one of those things now (IDEs/notebooks), but even that took a while, IMO.
Python is a weird case study for me. I'm not trying to flame war or anything- just pointing out my own blind spots and/or biases. But I just don't see much of anything redeeming about the language. It can be pretty easy to read, but I don't think most code I've seen actually is easy to read/follow.
care to elaborate?
What’s making the PPX situation even worse is that they seem to break with every new release of the compiler.
With PPX, the barrier to use metaprogramming has become lower (especially compared to camlp4), resulting in most modern Ocaml codebases depending on it. But the ergonomics of the end-to-end software delivery have not really followed: the fact that PPX's break between compiler versions means that in practice, a compiler upgrade becomes a very costly thing to do. It is difficult to make the case for this in an industrial setting, where languages with almost religious backwards compatibility are common (Java, C++, even Go). For Ocaml, it is especially sad, because the core language is already quite powerful and expressive, lowering the need for metaprogramming (imo).
For scenarios where code generation is needed, I prefer a separate code generation step, which produces explicit "standard" code (e.g. like protoc)