#system = null; # (This actually does nothing more than setting »config.nixpkgs.system« (which is the same as »config.nixpkgs.buildPlatform.system«) and can be null/unset here.)
# These are passed as »extraModules« module argument and can thus be reused when defining containers and such (so define as much stuff as possible here).
# There is, unfortunately, no way to directly pass modules into all containers. Each container will need to be defined with »config.containers."${name}".config.imports = extraModules«.
# (One could do that automatically by defining »options.security.containers = lib.mkOption { type = lib.types.submodule (cfg: { options.config = lib.mkOption { apply = _:_.extendModules { modules = extraModules; }; }); }«.)
# (This is already set during module import, while »_module.args« only becomes available during module evaluation (before that, using it causes infinite recursion). Since it can't be ensured that this is set in every circumstance where »extraModules« are being used, it should generally not be used to set custom arguments.)
# Given either a list (or attr set) of »files« (paths to ».nix« or ».nix.md« files for dirs with »default.nix« files in them) or a »dir« path (and optionally a list of base names to »exclude« from it), this builds the NixOS configuration for each host (per file) in the context of all configs provided.
# If »files« is an attr set, exactly one host with the attribute's name as hostname is built for each attribute. Otherwise the default is to build for one host per configuration file, named as the file name without extension or the sub-directory name. Setting »${preface'}.instances« can override this to build the same configuration for those multiple names instead (the specific »name« is passed as additional »moduleArgs« to the modules and can thus be used to adjust the config per instance).
# All other arguments are as specified by »mkSystemsFlake« and are passed to »mkNixosConfiguration«.
nixosArgs=(args.nixosArgsor{})//{specialArgs=(args.nixosArgs.specialArgsor{})//{inheritpreface;};};# make this available early, and only for the main evaluation (+specialisations, -containers)
# Builds a system of NixOS hosts and exports them, plus »apps« and »devShells« to manage them, as flake outputs.
# All arguments are optional, as long as the default can be derived from the other arguments as passed.
mkSystemsFlake=args@{
# An attrset of imported Nix flakes, for example the argument(s) passed to the flake »outputs« function. All other arguments are optional (and have reasonable defaults) if this is provided and contains »self« and the standard »nixpkgs«. This is also the second argument passed to the individual host's top level config files.
inputs?{},
# Arguments »{ files, dir, exclude, }« to »mkNixosConfigurations«, see there for details. May also be a list of those attrsets, in which case those multiple sets of hosts will be built separately by »mkNixosConfigurations«, allowing for separate sets of »peers« passed to »mkNixosConfiguration«. Each call will receive all other arguments, and the resulting sets of hosts will be merged.
systems?({dir="${inputs.self}/hosts";exclude=[];}),# TODO: (before nix 2.14) this is not relative to the flake.nix, but relative to the root of the repo
# List of Modules to import for all hosts, in addition to the default ones in »nixpkgs«. The host-individual module should selectively enable these. Defaults to ».nixosModules.default« of all »moduleInputs«/»inputs« (including »inputs.self«).
modules?(getModulesFromInputsmoduleInputs),
# (Subset of) »inputs« that »modules« will be used from. Example: »{ inherit (inputs) self flakeA flakeB; }«.
moduleInputs?inputs,
# List of additional modules to import for all hosts.
extraModules?[],
# List of overlays to set as »config.nixpkgs.overlays«. Defaults to ».overlays.default« of all »overlayInputs«/»inputs« (incl. »inputs.self«).
overlays?(getOverlaysFromInputsoverlayInputs),
# (Subset of) »inputs« that »overlays« will be used from. Example: »{ inherit (inputs) self flakeA flakeB; }«.
overlayInputs?inputs,
# Additional arguments passed to each module evaluated for the host config (if that module is defined as a function).
moduleArgs?{},
# The »nixosSystem« function defined in »<nixpkgs>/flake.nix«, or equivalent.
nixosSystem?inputs.nixpkgs.lib.nixosSystem,
# If provided, this will be set as »config.nixpkgs.buildPlatform« for all hosts, which in turn enables cross-compilation for all hosts whose »config.nixpkgs.hostPlatform« (the architecture they will run on) does not expand to the same value. Without this, building for other platforms may still work (slowly) if »boot.binfmt.emulatedSystems« on the building system is configured for the respective target(s).
## The platforms for which the setup scripts (installation & maintenance/debugging) will be defined. Should include the ».buildPlatform« and/or the target system's »config.nixpkgs.hostPlatform«.
## If provided, then change the name of each output attribute by passing it through this function. Allows exporting of multiple variants of a repo's hosts from a single flake (by then merging the results):
# if the (now) first arg is »bash« or there are no args, re-execute this script as bash »--init-file«, starting an interactive bash in the context of the script
if!PATH=$hostPath"$self"bash;then'$control'$status;fi# »|| '$control'« as an error-catch
#if ! ${pkgs.bashInteractive}/bin/bash --init-file ${system.config.environment.etc.bashrc.source} ; then '$control' $status ; fi # »|| '$control'« as an error-catch
