kubenix/modules/helm.nix

# helm defines kubenix module with options for using helm charts
# with kubenix
{
  config,
  lib,
  pkgs,
  helm,
  ...
}:
with lib; let
  cfg = config.kubernetes.helm;

  globalConfig = config;

  recursiveAttrs = mkOptionType {
    name = "recursive-attrs";
    description = "recursive attribute set";
    check = isAttrs;
    merge = loc: foldl' (res: def: recursiveUpdate res def.value) {};
  };

  parseApiVersion = apiVersion: let
    splitted = splitString "/" apiVersion;
  in {
    group =
      if length splitted == 1
      then "core"
      else head splitted;
    version = last splitted;
  };
in {
  imports = [./k8s.nix];

  options.kubernetes.helm = {
    instances = mkOption {
      description = "Attribute set of helm instances";
      type = types.attrsOf (types.submodule ({
        config,
        name,
        ...
      }: {
        options = {
          name = mkOption {
            description = "Helm release name";
            type = types.str;
            default = name;
          };

          chart = mkOption {
            description = "Helm chart to use";
            type = types.package;
          };

          namespace = mkOption {
            description = "Namespace to install helm chart to";
            type = types.nullOr types.str;
            default = null;
          };

          values = mkOption {
            description = "Values to pass to chart";
            type = recursiveAttrs;
            default = {};
          };

          kubeVersion = mkOption {
            description = "Kubernetes version to build chart for";
            type = types.str;
            default = globalConfig.kubernetes.version;
          };

          overrides = mkOption {
            description = "Overrides to apply to all chart resources";
            type = types.listOf types.unspecified;
            default = [];
          };

          overrideNamespace = mkOption {
            description = "Whether to apply namespace override";
            type = types.bool;
            default = true;
          };

          objects = mkOption {
            description = "Generated kubernetes objects";
            type = types.listOf types.attrs;
            default = [];
          };
        };

        config.overrides = mkIf (config.overrideNamespace && config.namespace != null) [
          {
            metadata.namespace = config.namespace;
          }
        ];

        config.objects = importJSON (helm.chart2json {
          inherit (config) chart name namespace values kubeVersion;
        });
      }));
      default = {};
    };
  };

  config = {
    # expose helm helper methods as module argument
    _module.args.helm = import ../lib/helm {inherit pkgs;};

    kubernetes.api.resources = mkMerge (flatten (mapAttrsToList
      (
        _: instance:
          map
          (object: let
            apiVersion = parseApiVersion object.apiVersion;
            name = object.metadata.name;
          in {
            "${apiVersion.group}"."${apiVersion.version}".${object.kind}."${name}" = mkMerge ([
                object
              ]
              ++ instance.overrides);
          })
          instance.objects
      )
      cfg.instances));
  };
}