Re: Versioned Tree-sitter parser libraries

[Yuan Fu]

> On Apr 17, 2023, at 10:03 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Sun, 16 Apr 2023 20:03:50 -0700
>> Cc: Peter Oliver <p.d.oliver@mavit.org.uk>,
>> emacs-devel@gnu.org
>> 
>>> If we were to load a versioned shared library, how would Emacs know
>>> which version to load?
>> 
>> Another thing is that tree-sitter grammars don’t really have versions (API 
>> or ABI versions), except for a tree-sitter version.
> 
> AFAIR, there is an ABI version, and we even expose it to Lisp, no?

There is a version, but it’s kind of a internal/protocol version between 
tree-sitter library and tree-sitter grammars, and I don’t think it’s a standard 
ABI version per se.

> 
>>>> The background to this question is that I’m thinking about packaging 
>>>> Tree-sitter parsers as RPMs for Fedora 
>>>> (https://pagure.io/tree-sitter-json/blob/rawhide/f/tree-sitter-json.spec). 
>>>>  Typical Fedora practice 
>>>> (https://docs.fedoraproject.org/en-US/packaging-guidelines/#_devel_packages)
>>>>  is to assume that the unversioned symlink isn’t required for regular use, 
>>>> and to place it in a …-devel subpackage that wouldn’t usually be installed.
>>> 
>>> That practice is fine for when a program is linked against the
>>> library, because the -lFOO linker switch is supposed to take care of
>>> that, and Emacs doesn't need to know which version is being used.  But
>>> here we load the shared libraries at run time, so we must know their
>>> names.  These names are explicitly mentioned in the Emacs sources.
>> 
>> 
>> Since Emacs requests/hopes the package manager or the system will provide 
>> the grammars, it seems a good idea to support the common way libraries tend 
>> to be named. Even maybe just a additional look up for only xxx.0.0, since 
>> grammars don’t have ABI versions, at least for now.
> 
> I don't think I understand what you suggest in practical terms.  What
> does it mean "additional look up for only xxx.0.0"? and why only
> xxx.0.0?

I was suggesting that we do recognize ABI versions, but since tree-sitter 
grammars don’t really have a ABI version, and the version extension in 
filenames are just there by convention (of Fedora), we can expect the version 
extension to be always 0.0, should there be one.

Yuan