29027fd1e1
Using pkgs.lib on the spine of module evaluation is problematic because the pkgs argument depends on the result of module evaluation. To prevent an infinite recursion, pkgs and some of the modules are evaluated twice, which is inefficient. Using ‘with lib’ prevents this problem.
1.3 KiB
1.3 KiB
{ config, lib, pkgs, ... }:
with lib;
let
failed = map (x: x.message) (filter (x: !x.assertion) config.assertions);
showWarnings = res: fold (w: x: builtins.trace "warning: ${w}" x) res config.warnings;
in
{
options = {
assertions = mkOption {
type = types.listOf types.unspecified;
internal = true;
default = [];
example = [ { assertion = false; message = "you can't enable this for that reason"; } ];
description = ''
This option allows modules to express conditions that must
hold for the evaluation of the system configuration to
succeed, along with associated error messages for the user.
'';
};
warnings = mkOption {
internal = true;
default = [];
type = types.listOf types.string;
example = [ "The `foo' service is deprecated and will go away soon!" ];
description = ''
This option allows modules to show warnings to users during
the evaluation of the system configuration.
'';
};
};
config = {
# This option is evaluated always. Thus the assertions are checked
# as well. Hacky!
environment.systemPackages = showWarnings (
if [] == failed then []
else throw "\nFailed assertions:\n${concatStringsSep "\n" (map (x: "- ${x}") failed)}");
};
}
with lib;
let
failed = map (x: x.message) (filter (x: !x.assertion) config.assertions);
showWarnings = res: fold (w: x: builtins.trace "warning: ${w}" x) res config.warnings;
in
{
options = {
assertions = mkOption {
type = types.listOf types.unspecified;
internal = true;
default = [];
example = [ { assertion = false; message = "you can't enable this for that reason"; } ];
description = ''
This option allows modules to express conditions that must
hold for the evaluation of the system configuration to
succeed, along with associated error messages for the user.
'';
};
warnings = mkOption {
internal = true;
default = [];
type = types.listOf types.string;
example = [ "The `foo' service is deprecated and will go away soon!" ];
description = ''
This option allows modules to show warnings to users during
the evaluation of the system configuration.
'';
};
};
config = {
# This option is evaluated always. Thus the assertions are checked
# as well. Hacky!
environment.systemPackages = showWarnings (
if [] == failed then []
else throw "\nFailed assertions:\n${concatStringsSep "\n" (map (x: "- ${x}") failed)}");
};
}