Re: opam packaging

On Mon, Nov 30, 2015 at 03:47:19PM -0500, Ashish Agarwal [email protected] [ocaml_beginners] wrote:
> On Thu, Nov 26, 2015 at 4:32 PM, Hendrik Boom [email protected]
> [ocaml_beginners] <[email protected]> wrote:
> 
> > Is this the right forum for questions like this?
> >
> Sure, although there is also the opam-devel list that could be used:
> http://lists.ocaml.org/listinfo/opam-devel
> 
> I do want to avoid confusion between mine and the official opam
> > packages of the same name.
> >
> You can do `opam repo priority`. Setting a higher priority to a repo gives
> it higher precedence. See:
> http://opam.ocaml.org/doc/Manual.html#Metadataprecedence
> 
> 
> > Perhaps all this is clearly discussed in documentatino somewhere. If so
> > I'd appreciate pointers to said documentation.
> >
> 
> See the "documentation" link from opam.ocaml.org, but in my experience the
> manual is out-of-date or missing many features.
> 
> (1) Where do I find the actual packages -- source and metadata in the
> > .opam directory? Presumably once I have this, it will be clearer hos to
> > proceed.
> >
> If I understand what you're trying to do correctly, you shouldn't need to
> know this. You just need to create another repository, and add it with
> `opam repo add`. In general, you shouldn't manually modify anything under
> your .opam directory.

So is the .opam a repository?  Or does it contain a repository?
And the various packages that opam will download for me, do they come 
from a net-accessinle repository?  Or each from its own?

And I'd have to set up another repository for my packages or my 
modified packages to reside in?

> 
> (2) What naming conventions are there to distinguish different versions
> > of a package so that specific ones are picked up by programs like
> > ocamlfind and ocamlbuild?
> >
> Note there is no connection between an opam package name, an ocamlfind
> package name, and an OCaml library name. Usually, they are of course
> somewhat similar, but there's nothing to enforce that.
> 
> You specifically mention "different versions of a package". With OPAM, you
> can only install multiple versions of the same package by putting them in
> different switches. Then when you do an `opam switch`, there is no choice
> about which version ocamlfind or ocamlbuild will pick since within a switch
> there is only one version visible.

I'll have to read up on switches before I have follow-up questions.

> 
> (3) Once I do have package source code and have edited it
> >
> Again, if I'm understanding your goals correctly, you shouldn't be
> modifying a packages source code, only its opam metadata.

I want to add functionality to an existing package, and/or fix things 
that I consider bugs, whether the original author does or not.
For that, I suspect I need to modify the source code.

When it's all working, I'd submit the changes upstream, and they can be 
accepted or not.

To find the source code, do I have to unpack the tarball under 
.opam/archives?  Or is there some way to identify a distributed revision 
management repository it might be better to pull from?

Thank you.

-- hendrik