Ludo, The self.options["openssl"].shared does set the option for openssl, but this is not different than providing `-o openssl:shared` on the command line; it uses this to determine which package was actually requested. Conan packages are also non-configurable in the end, stored as the hash of it's name and parameters. This is probably done while calculating the tree before installing/building everything, but once that tree is calculated, it is fixed.
Besides parameters determining the hash of the package, OpenSSL/2.1@memsharded/testing and openssl/1.0.2u are most certainly separate packages. Conan has this name/version@username/channel structure to help find alternatives (semver is supported), but otherwise those are completely different. On November 17, 2020 10:31:12 AM EST, "Ludovic Courtès" <l...@gnu.org> wrote: >Hi Stephen, > >(+Cc: guix-devel@gnu.org. You can post without being subscribed.) > >Stephen Christie <spc@e.email> skribis: > >> I have done a lot of work with the Conan package manager, a c++ >> language package manager, that has grown in capability. It is not >> fully functional, but works on the hash of the key parameters of the >> package (name, version, etc.) to find the right reproducible >> binary. Two important parameters are "options" and "settings". >> >> Options are per-package, and generally affect none below it. You can >> specify defaults for the options in the package, and also call for >> specific options on dependencies in package "recipes". There are also >> ways to define incompatibilities and substitutes. On the command >line, >> you can specify options with -o,--options, with no namespace needed >> for the package you are installing, and package:option to specify for >> other packages pulled in. I prefer this syntax to all the equal signs >> you proposed (though I defer if this is standard throughout >> Guix/Guile) >> >> Settings are more "system-wide", though being a language package >> manager, it does not have a "system". The same settings are applied >to >> the whole tree during an install, and are usually things like >> compiler, architecture, and build type. These settings are chosen >> through a profile file, of which there is a default generated for a >> given computer. Settings can also be set at the command line during >> install with -s,--settings, but of course there is no namespacing. >> >> https://docs.conan.io/en/latest/mastering/conditional.html >> >> I think there is a lot of good stuff in Conan that Guix could learn >> from. It's a lot closer in architecture than any of the traditional >> system package managers. > >Thanks for sharing Conan’s perspective on these issues! > >The settings/options distinction looks like a useful one. Like Pierre >suggested, it’d be nice to have options that apply to the whole graph >in >addition to per-package options like I was focusing on. > >Conan’s approach to conflicting options may not be applicable to Guix. >For instance, the manual above has this example: > > def configure(self): > # … > if self.settings.os == "Windows": > self.options["openssl"].shared = True > > def requirements(self): > # Or add a new requirement! > if self.options.testing: > self.requires("OpenSSL/2.1@memsharded/testing") > else: > self.requires("openssl/1.0.2u") > >In Guix, instead of stating that OpenSSL 1.0.2u is required or that it >needs to include shared libraries, you’d actually depend on a variant >of >OpenSSL that fulfills these constraints; by construction, you can be >sure you have the intended OpenSSL variant (generally speaking, a Guix >package dependency graph has zero degrees of liberty, unlike an >apt/Spack/Conan graph.) > >As for the syntax… yeah, we could find a shorthand. :-) The verbosity >in the examples I gave partly stems from the fact that these are >per-package parameters, so you need to specify which package it applies >to. With “global” parameters, we could have, say: > > guix install -P x11=false emacs > >meaning that the ‘x11’ parameter will be set to #f in all the packages >that have such a parameter. > >Thanks, >Ludo’. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
