option --version is buggy

[francoisthire]

lambdapi --version prints

Lambdapi %%VERSION%%

[rlepigre]

That's not a bug, that's a feature of Dune. Only releases have their version substituted.

[francoisthire]

Well If I do make install I expect to have something better than %%%VERSION%%%.

[francoisthire]

This is very frustrating because right now there is no easy way to know the current version of lambdapi.

[rlepigre]

I agree, I'm as pissed of as you are by how crappy dune is. I would expect a version number like devel-<commit hash>, but apparently that's not possible.

[rlepigre]

@francoisthire: I just discovered that if you install using opam pin then you get the version number.

[ejgallego]

You need to use the build-info library https://dune.readthedocs.io/en/stable/dune-libs.html#build-info

[rlepigre]

I find the idea of carrying build-system dependent code around in my project kind of worrying... But thanks @ejgallego! I did not know that already existed.

But anyway, is there any doc available for that library? I can't even find its source code in the middle of the whole dune repository. I'm hoping that it also provides installation paths.

[ejgallego]

I find the idea of carrying build-system dependent code around in my project kind of worrying... But thanks @ejgallego! I did not know that already existed.

The version problem is not an easy problem; in particular it is hard to maintain a proper incremental build. You don't the binary rebuilt on every hash change.

You can use build-info or else you can roll your own wrapper to git describe too, but then you have to be very careful as to avoid the rebuild problem.

Code for build-info is here BTW https://github.com/ocaml/dune/tree/master/otherlibs/build-info

[rlepigre]

OK, do since build-info does not allow to do what I want, I don't think it is worth using it. I'm personally OK with the current situation where releases get a version number, and you also get a version number if you pin the repository. I'd rather not implement the version stuff myself.

As for the other limitations, I think I'm gonna have to hack around.

[ejgallego]

since build-info does not allow to do what I want

What would you like it to do? At least for the original request in this issue, it should work.

[rlepigre]

Yeah, it would. But I also want to know where the lib directory used for the installation is (i.e., the result of opam var lib).

[ejgallego]

That's indeed your own ocaml/dune#1534 and ocaml/dune#1185 , IMHO it is better to have a small lookup function that considers different possibilities than to hardcode a path.

For example in Coq we set the data path at configure time, however in the build we can override in several ways so everything works (famous last words)

[rlepigre]

Exactly! This problem keeps coming up for me. And yeah, I would like to avoid hackish solutions, and would prefer to have some guarantees. But I guess I'll just rely on some lookup function to discover the configuration.

[ejgallego]

Lookup tends to be pretty convenient, IMHO rebuilding the binary on install is quite of a bit hammer to use just for this.