Re: [Caml-list] META file standards for ppx extensions

["Daniel Bünzli" <daniel.buenzli@erratique.ch>]

In the assemblage project we are quite interested in seeing packages as named entities providing flags/and or objects to use in a given command execution context (defined as pre-processing, compiling, linking, etc. see [1] for more details).

During the first build ("configure") we want to `ocamlfind query` packages for the right flags in each context and cache them so that we don't have to go through ocamlfind during the compilation (which slows down things quite a bit). 

Is there an invocation that allow us to get the flags or objects to use, the following don't seem to work:

> ocamlfind query -predicates ppx -pp lwt.ppx
> ocamlfind query -pp lwt.ppx 


and I don't see an obvious specifier for `-format` I can use. 

It would be nice in general if ocamlfind would allow us to use `ocamlfind query` in obvious ways so that we can exactly reproduce what it does when whatever `ocamlfind TOOL -pkg PKG1,PKG2,PKG3` is being invoked. 

I'm not working on this at the moment and don't have these things in my head but I remember that it proved to be quite challenging (if not impossible) to achieve that goal. 

Best,

Daniel

[1] http://samoht.github.io/assemblage/Assemblage.Ctx.html