Re: Versioned Tree-sitter parser libraries

[Yuan Fu <casouri@gmail.com>]

> On Apr 16, 2023, at 7:49 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> Date: Sun, 16 Apr 2023 15:20:51 +0100 (BST)
>> From: Peter Oliver <p.d.oliver@mavit.org.uk>
>> 
>> A number of Tree-sitter parsers include a Makefile that will install, e.g., /usr/lib/libtree-sitter-json.so.0.0.  However, I notice that Emacs 29.0.90 will find it only if there exists a symlink /usr/lib/libtree-sitter-json.so.
>> 
>> Is this desirable?
> 
> 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.

> 
>> 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.

Yuan