install: let nixos-anywhere determine where to build automatically

This fixes installing machines that don't have `system` defined i.e.
when running `clan machines install` with `--update-hardware-config`.

pkgs/clan-cli/clan_cli/machines/install.py

@@ -3,6 +3,7 @@ import logging
 import os
 import sys
 from dataclasses import dataclass, field
+from enum import Enum
 from pathlib import Path
 from tempfile import TemporaryDirectory
 
@@ -25,6 +26,12 @@ from clan_cli.vars.generate import generate_vars
 log = logging.getLogger(__name__)
 
 
+class BuildOn(Enum):
+    AUTO = "auto"
+    LOCAL = "local"
+    REMOTE = "remote"
+
+
 @dataclass
 class InstallOptions:
     machine: Machine
@@ -33,7 +40,7 @@ class InstallOptions:
     debug: bool = False
     no_reboot: bool = False
     phases: str | None = None
-    build_on_remote: bool = False
+    build_on: BuildOn | None = None
     nix_options: list[str] = field(default_factory=list)
     update_hardware_config: HardwareConfig = HardwareConfig.NONE
     password: str | None = None
@@ -122,10 +129,8 @@ def install_machine(opts: InstallOptions) -> None:
         if opts.identity_file:
             cmd += ["-i", str(opts.identity_file)]
 
-        if opts.build_on_remote:
+        if opts.build_on:
-            cmd.extend(["--build-on", "remote"])
+            cmd += ["--build-on", opts.build_on.value]
-        else:
-            cmd.extend(["--build-on", "auto"])
 
         if h.port:
             cmd += ["--ssh-port", str(h.port)]
@@ -210,7 +215,7 @@ def install_command(args: argparse.Namespace) -> None:
                 debug=args.debug,
                 no_reboot=args.no_reboot,
                 nix_options=args.option,
-                build_on_remote=args.build_on_remote,
+                build_on=BuildOn(args.build_on) if args.build_on is not None else None,
                 update_hardware_config=HardwareConfig(args.update_hardware_config),
                 password=password,
                 identity_file=args.identity_file,
@@ -241,10 +246,10 @@ def register_install_parser(parser: argparse.ArgumentParser) -> None:
         help="Host key (.ssh/known_hosts) check mode.",
     )
     parser.add_argument(
-        "--build-on-remote",
+        "--build-on",
-        action="store_true",
+        choices=[x.value for x in BuildOn],
-        help="build the NixOS configuration on the remote machine",
+        default=None,
-        default=False,
+        help="where to build the NixOS configuration",
     )
     parser.add_argument(
         "--yes",

pkgs/clan-cli/clan_cli/machines/machines.py

@@ -4,15 +4,13 @@ import logging
 from dataclasses import dataclass, field
 from functools import cached_property
 from pathlib import Path
-from time import time
 from typing import TYPE_CHECKING, Any, Literal
 
-from clan_cli.cmd import RunOpts, run_no_stdout
 from clan_cli.errors import ClanError
 from clan_cli.facts import public_modules as facts_public_modules
 from clan_cli.facts import secret_modules as facts_secret_modules
 from clan_cli.flake import Flake
-from clan_cli.nix import nix_build, nix_config, nix_eval, nix_test_store
+from clan_cli.nix import nix_config, nix_test_store
 from clan_cli.ssh.host import Host
 from clan_cli.ssh.host_key import HostKeyCheck
 from clan_cli.ssh.parse import parse_deployment_address
@@ -64,41 +62,6 @@ class Machine:
             f"nixosConfigurations.{self.name}.pkgs.hostPlatform.system"
         )
 
-    @property
-    def can_build_locally(self) -> bool:
-        config = nix_config()
-        if self.system == config["system"] or self.system in config["extra-platforms"]:
-            return True
-
-        nix_code = f"""
-            let
-              flake = builtins.getFlake("path:{self.flake.store_path}?narHash={self.flake.hash}");
-            in
-              (flake.inputs.nixpkgs.legacyPackages.{self.system}.runCommandNoCC "clan-can-build-{int(time())}" {{ }} "touch $out").drvPath
-        """
-
-        unsubstitutable_drv = json.loads(
-            run_no_stdout(
-                nix_eval(
-                    [
-                        "--expr",
-                        nix_code,
-                    ]
-                ),
-                opts=RunOpts(prefix=self.name),
-            ).stdout.strip()
-        )
-
-        try:
-            run_no_stdout(
-                nix_build([f"{unsubstitutable_drv}^*"]), opts=RunOpts(prefix=self.name)
-            )
-        except Exception as e:
-            self.debug("failed to build test derivation", exc_info=e)
-            return False
-        else:
-            return True
-
     @property
     def deployment(self) -> dict:
         if self.cached_deployment is not None: