From aa825b87a6a16a8a663e14f52155bc924d28bad1 Mon Sep 17 00:00:00 2001
From: Pacman99 <pachum99@gmail.com>
Date: Tue, 27 Apr 2021 10:26:45 -0700
Subject: [PATCH] auto import hosts in flake.nix this allows host-specific
 settings to be overriden with mkMerge

---
 doc/concepts/hosts.md | 56 ++++++++++++++++++++++++-------------------
 flake.lock            |  2 +-
 flake.nix             |  9 ++++---
 lib/attrs.nix         |  8 +++++++
 lib/flake.nix         |  5 ++--
 5 files changed, 48 insertions(+), 32 deletions(-)

diff --git a/doc/concepts/hosts.md b/doc/concepts/hosts.md
index 770fa51b..1fa90284 100644
--- a/doc/concepts/hosts.md
+++ b/doc/concepts/hosts.md
@@ -1,18 +1,24 @@
 # Hosts
 
 Nix flakes contain an output called `nixosConfigurations` declaring an
-attribute set of valid NixOS systems. To create hosts, you can use the 
-`nixos.hosts` argument and pass `modules` to each host. Host-specific modules
-typically go in the `hosts` folder of the template.
+attribute set of valid NixOS systems. To simplify the management and creation
+of these hosts, devos automatically imports every _.nix_ file inside this
+directory to the mentioned attribute set, applying the projects defaults to
+each. The only hard requirement is that the file contain a valid NixOS module.
 
-Each host should follow a certain channel to define the `pkgs` of that host.
-You can use the `nixos.hostDefaults` to set defaults and global modules for all
-hosts.
+As an example, a file `hosts/system.nix` will be available via the flake
+output `nixosConfigurations.system`. You can have as many hosts as you want
+and all of them will be automatically imported based on their name.
 
 For each host, the configuration automatically sets the `networking.hostName`
-attribute to the name of the host. This is for convenience, since `nixos-rebuild`
-automatically searches for a configuration matching the current systems hostname
-if one is not specified explicitly.
+attribute to the name of the file minus the _.nix_ extension. This is for
+convenience, since `nixos-rebuild` automatically searches for a configuration
+matching the current systems hostname if one is not specified explicitly.
+
+You can set channels, systems, and add extra modules to each host by editing the
+`nixos.hosts` argument in flake.nix. This is the perfect place to import
+host specific modules from external sources, such as the
+[nixos-hardware][nixos-hardware] repository.
 
 It is recommended that the host modules only contain configuration information
 specific to a particular piece of hardware. Anything reusable across machines
@@ -21,16 +27,29 @@ is best saved for [profile modules](./profiles.md).
 This is a good place to import sets of profiles, called [suites](./suites.md),
 that you intend to use on your machine.
 
-Additionally, you can pass modules from [nixos-hardware][nixos-hardware] in the
-`modules` argument for relevant hosts.
 
 ## Example
 
+flake.nix:
+```nix
+{
+  nixos.hosts = mkMerge [
+    (devos.lib.importHosts ./hosts)
+    {
+      librem = {
+        channelName = "latest";
+        modules = [ hardware.purism-librem-13v3 ];
+      };
+    }
+  ];
+}
+```
+
 hosts/librem.nix:
 ```nix
-{ suites, hardware, ... }:
+{ suites, ... }:
 {
-  imports = suites.laptop ++ [ hardware.purism-librem-13v3 ];
+  imports = suites.laptop;
 
   boot.loader.systemd-boot.enable = true;
   boot.loader.efi.canTouchEfiVariables = true;
@@ -39,15 +58,4 @@ hosts/librem.nix:
 }
 ```
 
-flake.nix
-```nix
-{
-  nixos.hosts.librem = {
-    system = "aarch64-linux";
-    modules = ./hosts/librem.nix;
-  };
-}
-```
-
-
 [nixos-hardware]: https://github.com/NixOS/nixos-hardware
diff --git a/flake.lock b/flake.lock
index 7841db57..91c20fdd 100644
--- a/flake.lock
+++ b/flake.lock
@@ -81,7 +81,7 @@
         "utils": "utils_2"
       },
       "locked": {
-        "narHash": "sha256-r+OPJF65PToVQK1ll2INAYmIV3zmnDzWBpGLx8m4aVo=",
+        "narHash": "sha256-hpvEXcpq85cDKi0F5UUsuMVISKlk8hgVJiz5FF29RwA=",
         "path": "./lib",
         "type": "path"
       },
diff --git a/flake.nix b/flake.nix
index 5468f5a5..d30cc3a9 100644
--- a/flake.nix
+++ b/flake.nix
@@ -61,11 +61,10 @@
             home.nixosModules.home-manager
           ];
         };
-        hosts = {
-          NixOS = {
-            modules = ./hosts/NixOS.nix;
-          };
-        };
+        hosts = nixos.lib.mkMerge [
+          (devos.lib.importHosts ./hosts)
+          { /* set host specific properties here */ }
+        ];
         profiles = [ ./profiles ./users ];
         suites = { profiles, users, ... }: with profiles; {
           base = [ cachix core users.nixos users.root ];
diff --git a/lib/attrs.nix b/lib/attrs.nix
index d1bc7648..93f79583 100644
--- a/lib/attrs.nix
+++ b/lib/attrs.nix
@@ -30,6 +30,14 @@ rec {
       value = import path;
     });
 
+  importHosts = dir:
+    lib.os.recImport {
+      inherit dir;
+      _import = base: {
+        modules = import "${toString dir}/${base}.nix";
+      };
+    };
+
   concatAttrs = lib.fold (attr: sum: lib.recursiveUpdate sum attr) { };
 
   # Filter out packages that support given system and follow flake check requirements
diff --git a/lib/flake.nix b/lib/flake.nix
index 17e069c2..2513311d 100644
--- a/lib/flake.nix
+++ b/lib/flake.nix
@@ -48,7 +48,8 @@
             safeReadDir
             pathsToImportedAttrs
             concatAttrs
-            filterPackages;
+            filterPackages
+            importHosts;
           inherit (lists) pathsIn collectProfiles unifyOverlays;
           inherit (strings) rgxToString;
           inherit modules;
@@ -60,7 +61,7 @@
     {
       lib = utils.lib // {
         inherit (lib)
-          mkFlake pathsIn;
+          mkFlake pathsIn importHosts;
       };
 
     }