Conditional library dependencies in dune-project

Question

This seems like it should be obvious bug how do I have a conditional dependency in dune-project? Specifically I want to depend on a library but only on Unix-like systems:

(package
  (name foo)
  (depends
    (linenoise (and (>= 1.1.0) (= %{os_type} "Unix")))))))))

That doesn't actually work because it is invalid syntax. The only examples of %{os_type} I found were for enabled_if which only can disable or enable an entire package. It doesn't work for dependencies apparently.

This is really easy in Rust; surely OCaml can do this?

Rawley Fowler · Accepted Answer · 2025-09-15 03:55:25Z

1

What you want is this:

(package
  (name foo)
  (depends
    (linenoise (and (>= 1.1.0) (= :os "linux")))))

OPAM will convert :os to a OCaml value by the same name os in the OPAM source code. This will be whatever OPAM thinks your operating system is. Note this value can be "" in some cases so be careful.

answered Sep 15 at 3:55

Rawley Fowler

3,13712 silver badges21 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Conditional library dependencies in dune-project

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related