Modular, context-aware and aspect-oriented dendritic Nix configurations.
Discussions: https://oeiuwq.zulipchat.com/join/nqp26cd4kngon6mo3ncgnuap/
den.oeiuwq.com
configurations
den
dendritic
nix
aspect
oriented
feat(core): `aspect.meta` allow attaching freeform attributes to aspects (#376)
This can be used for aspect introspection or for passing metadata
attached to aspects themselves.
---
@drupol would love your input on this one, does this look good to you?
authored by
Victor Borja
and committed by
GitHub
7e84abfd
aa99f5eb
+222
-13
+48
docs/src/content/docs/guides/configure-aspects.mdx
+48
docs/src/content/docs/guides/configure-aspects.mdx
···
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Parametric functions in `den.default.includes` are evaluated at every context
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stage. Use `den.lib.take.exactly` if a function should only run in specific contexts.
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</Aside>
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## Aspect Meta-Data
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Aspects have a `meta` submodule that can be used to attach meta-data
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at the aspect-level.
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This is useful for introspection, for example, using some key to filter out aspects
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or communicate information about aspects to other tooling like graph generators.
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Since `.meta` is a freeformType you can add any custom attribute or import a module on it.
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The following are default `meta.*` attributes defined by Den:
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```nix
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aspect.name # "den.aspects.igloo"
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meta.loc # the location [ "den" "aspects" "igloo" ] from where name is derived.
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meta.file # the first file where this aspect was defined.
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meta.self # a reference to the aspect module `config`.
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```
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You can acess meta values by referencing an aspect:
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```nix
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den.aspects.igloo.meta.name
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```
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Or if an aspect needs to access its own meta data as part of its parametric functor,
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it can do something like:
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```nix
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den.aspects.foo =
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{ config, lib, ... }: # module args to access `config.meta`
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{
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meta.foo = "bar";
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__functor = self: ctx:
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if config.meta.foo == "bar"
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then { } # do nothing, skip.
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{
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includes = filter (i: someCondition i) self.includes;
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};
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}
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```
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+21
-8
nix/lib/aspects/resolve.nix
+21
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nix/lib/aspects/resolve.nix
···
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inherit (den.lib) canTake take;
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apply =
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provided: args:
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let
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res = if canTake.upTo args provided then take.upTo provided args else provided;
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mod =
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den.lib.aspects.types.aspectType.merge
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[ ]
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[
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{
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file = "<curried>";
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value = res;
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}
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];
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in
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if lib.isFunction res then mod else res;
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resolve =
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class: prev-chain: provided:
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let
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aspect = if canTake.upTo args provided then take.upTo provided args else provided;
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aspect = apply provided { inherit class aspect-chain; };
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aspect-chain = prev-chain ++ [ provided ] ++ (lib.optional (provided != aspect) aspect);
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args = {
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inherit aspect class aspect-chain;
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};
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imports =
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(lib.optional (aspect ? ${class}) aspect.${class})
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++ (map (resolve class aspect-chain) (aspect.includes or [ ]));
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classModule = lib.optional (aspect ? ${class}) (
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lib.setDefaultModuleLocation "${class}@${aspect.name}" aspect.${class}
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);
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imports = classModule ++ (map (resolve class aspect-chain) (aspect.includes or [ ]));
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in
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{
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inherit imports;
+35
-5
nix/lib/aspects/types.nix
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-5
nix/lib/aspects/types.nix
···
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};
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isProviderFn = canTake.upTo {
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aspect = true;
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aspect-chain = true;
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class = true;
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};
···
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let
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sub = aspectSubmodule cnf;
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in
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sub
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// {
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merge = loc: defs: sub.merge loc defs;
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sub // { merge = mergeWithAspectMeta sub; };
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mergeWithAspectMeta =
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sub: loc: defs:
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sub.merge loc (
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defs
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++ [
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{
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file = (lib.head defs).file;
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value = aspectMeta loc defs;
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}
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]
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);
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aspectMeta =
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loc: defs:
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{ config, ... }:
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let
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names = map (x: if builtins.isString x then x else "<anon>") loc;
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nameFromLoc = lib.concatStringsSep "." names;
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in
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{
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name = nameFromLoc;
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meta.file = (lib.last defs).file;
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meta.loc = loc;
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};
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aspectSubmodule =
···
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{ name, config, ... }:
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{
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freeformType = lib.types.lazyAttrsOf lib.types.deferredModule;
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config._module.args.aspect = config;
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imports = [ (lib.mkAliasOptionModule [ "_" ] [ "provides" ]) ];
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options = {
···
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defaultText = lib.literalExpression "name";
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default = "Aspect ${name}";
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type = lib.types.str;
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};
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meta = lib.mkOption {
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description = "Aspect attached meta data";
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type = lib.types.submodule {
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freeformType = lib.types.lazyAttrsOf lib.types.unspecified;
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self = config;
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};
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defaultText = lib.literalExpression "{ }";
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default = { };
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};
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includes = lib.mkOption {
+118
templates/ci/modules/features/aspect-meta.nix
+118
templates/ci/modules/features/aspect-meta.nix
···
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{ denTest, ... }:
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{
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flake.tests.aspect-meta = {
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test-meta-can-be-referenced = denTest (
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{ den, funnyNames, ... }:
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{
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den.aspects.foo = {
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funny.names = [ den.aspects.foo.meta.nick ];
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meta.nick = "McLoving";
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};
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expr = funnyNames den.aspects.foo;
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expected = [ "McLoving" ];
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}
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);
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test-meta-can-be-self-referenced = denTest (
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{ den, funnyNames, ... }:
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{
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den.aspects.foo =
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{ config, ... }:
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{
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funny.names = [ config.meta.nick ];
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meta.nick = "McLoving";
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};
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expr = funnyNames den.aspects.foo;
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expected = [ "McLoving" ];
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}
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);
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test-name-can-be-referenced = denTest (
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{ den, funnyNames, ... }:
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{
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den.aspects.foo = {
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funny.names = [ den.aspects.foo.name ];
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};
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expr = funnyNames den.aspects.foo;
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expected = [ "den.aspects.foo" ];
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}
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);
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test-name-can-be-self-referenced = denTest (
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{ den, funnyNames, ... }:
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{
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den.aspects.foo =
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{ config, ... }:
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{
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funny.names = [ config.name ];
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};
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expr = funnyNames den.aspects.foo;
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expected = [ "den.aspects.foo" ];
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}
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);
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test-meta-keys-at-host-aspect = denTest (
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{
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den,
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igloo,
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lib,
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...
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}:
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{
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den.hosts.x86_64-linux.igloo = { };
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den.aspects.igloo.includes = [ den.aspects.foo ];
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den.aspects.foo =
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{ host }:
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{
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nixos.environment.sessionVariables = {
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KEYS = lib.attrNames den.aspects.foo.meta.self.meta;
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};
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};
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expr = {
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inherit (igloo.environment.sessionVariables)
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KEYS
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;
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};
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expected.KEYS = "file:loc:self";
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}
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);
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test-meta-keys-at-host-fixpoint = denTest (
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{
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den,
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igloo,
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lib,
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...
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}:
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{
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den.hosts.x86_64-linux.igloo = { };
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den.aspects.igloo.includes = [ den.aspects.foo ];
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den.aspects.foo =
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{ host }:
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{ config, lib, ... }:
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{
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nixos.environment.sessionVariables = {
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KEYS = lib.attrNames config.meta;
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};
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meta.foo = 12;
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};
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expr = {
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inherit (igloo.environment.sessionVariables)
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KEYS
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;
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};
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expected.KEYS = "file:foo:loc:self";
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}
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);
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};
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}