refactor(ops/nixos): add "depot" argument to NixOS modules r/2404

For the moment I've opted to not import all of the other things we'd
usually provide to things imports via readTree, because I think it's a
bit dangerous to accidentally overwrite things like NixOS' notion of
"lib" with our own version.

So for the moment, baseModule provides only "depot".

Change-Id: I3db9132a3d9227055d4c1b00f02effcb84edcc53
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2760
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>

1 files changed, 13 insertions, 5 deletions

diff --git a/ops/nixos/default.nix b/ops/nixos/default.nix
index 312d762f246b..1d1e8da192b8 100644
--- a/ops/nixos/default.nix
+++ b/ops/nixos/default.nix
@@ -19,15 +19,23 @@ rec {
 
   allSystems = import ./all-systems.nix args;
 
-  nixosFor = configuration: depot.third_party.nixos {
-    configuration = {
-      inherit depot;
+  # This provides our standard set of arguments to all NixOS modules.
+  baseModule = { ... }: {
+    _module.args = {
+      inherit (args) depot;
+    };
+  };
+
+  nixosFor = configuration: (depot.third_party.nixos {
+    configuration = { ... }: {
       imports = [
+        baseModule
+        "${depot.depotPath}/ops/nixos/depot.nix"  # TODO(lukegb): remove this once config.depot is no longer referenced.
         configuration
-        "${depot.depotPath}/ops/nixos/depot.nix"
       ];
+      config.depot = depot;
     };
-  };
+  });
 
   findSystem = hostname:
     (findFirst