feat: allow to customize devcontainers

.devcontainer.json

@@ -1,9 +1,12 @@
 {
-  "image": "ghcr.io/cachix/devenv:latest",
-  "overrideCommand": false,
   "customizations": {
     "vscode": {
-      "extensions": ["mkhl.direnv"]
+      "extensions": [
+        "bbenoist.Nix"
+      ]
     }
-  }
+  },
+  "image": "ghcr.io/cachix/devenv:latest",
+  "overrideCommand": false,
+  "updateContentCommand": "devenv ci"
 }

devenv.nix

@@ -12,6 +12,7 @@
   languages.python.venv.enable = true;
 
   devcontainer.enable = true;
+  devcontainer.settings.customizations.vscode.extensions = [ "bbenoist.Nix" ];
   difftastic.enable = true;
 
   # bin/mkdocs serve --config-file mkdocs.insiders.yml

src/modules/integrations/devcontainer.nix

@@ -1,21 +1,57 @@
 { pkgs, lib, config, ... }:
 
 let
-  file = pkgs.writeText "devcontainer.json" ''
-    {
-      "image": "ghcr.io/cachix/devenv:latest",
-      "overrideCommand": false,
-      "customizations": {
-        "vscode": {
-          "extensions": ["mkhl.direnv"]
-        }
-      }
-    }
-  '';
+  cfg = config.devcontainer;
+  settingsFormat = pkgs.formats.json { };
+  file = settingsFormat.generate "devcontainer.json" cfg.settings;
 in
 {
   options.devcontainer = {
     enable = lib.mkEnableOption "generation .devcontainer.json for devenv integration";
+
+    settings = lib.mkOption {
+      type = lib.types.submodule {
+        freeformType = settingsFormat.type;
+
+        options.image = lib.mkOption {
+          type = lib.types.str;
+          default = "ghcr.io/cachix/devenv:latest";
+          description = lib.mdDoc ''
+            The name of an image in a container registry.
+          '';
+        };
+
+        options.overrideCommand = lib.mkOption {
+          type = lib.types.anything;
+          default = false;
+          description = lib.mdDoc ''
+            Override the default command.
+          '';
+        };
+
+        options.updateContentCommand = lib.mkOption {
+          type = lib.types.anything;
+          default = "devenv ci";
+          description = lib.mdDoc ''
+            Command to run after container creation.
+          '';
+        };
+
+        options.customizations.vscode.extensions = lib.mkOption {
+          type = lib.types.listOf lib.types.str;
+          default = [ "mkhl.direnv" ];
+          description = lib.mdDoc ''
+            List of preinstalled VSCode extensions.
+          '';
+        };
+      };
+
+      default = { };
+
+      description = lib.mdDoc ''
+        Devcontainer settings.
+      '';
+    };
   };
 
   config = lib.mkIf config.devcontainer.enable {