nixos-rebuild-ng: add from_host in nix.copy_closure

pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/__init__.py

@@ -210,7 +210,7 @@ def execute(argv: list[str]) -> None:
                         no_out_link=True,
                         **build_flags,
                     )
-                nix.copy_closure(path_to_config, target_host, **copy_flags)
+                nix.copy_closure(path_to_config, target_host, None, **copy_flags)
                 nix.set_profile(profile, path_to_config, target_host, sudo=args.sudo)
             nix.switch_to_configuration(
                 path_to_config,
@@ -253,7 +253,7 @@ def execute(argv: list[str]) -> None:
                 nix.switch_to_configuration(
                     path_to_config,
                     action,
-                    target_host,
+                    target_host=None,
                     sudo=args.sudo,
                     specialisation=args.specialisation,
                 )

pkgs/by-name/ni/nixos-rebuild-ng/src/nixos_rebuild/nix.py

@@ -27,10 +27,14 @@ logger = logging.getLogger(__name__)
 
 def copy_closure(
     closure: Path,
-    target_host: Remote | None,
+    to_host: Remote | None,
+    from_host: Remote | None = None,
     **copy_flags: Args,
 ) -> None:
-    host = target_host
+    """Copy a nix closure to or from host to localhost.
+
+    Also supports copying a closure from a remote to another remote."""
+    host = to_host or from_host
     if not host:
         return
 
@@ -38,11 +42,12 @@ def copy_closure(
         [
             "nix-copy-closure",
             *dict_to_flags(copy_flags),
-            "--to",
+            "--to" if to_host else "--from",
             host.host,
             closure,
         ],
         extra_env={"NIX_SSHOPTS": " ".join(host.opts)},
+        remote=from_host if to_host else None,
     )
 
 

pkgs/by-name/ni/nixos-rebuild-ng/src/tests/test_nix.py

@@ -18,11 +18,28 @@ def test_copy_closure(mock_run: Any) -> None:
     n.copy_closure(closure, None)
     mock_run.assert_not_called()
 
-    target_host = m.Remote("user@host", ["--ssh", "opt"], None)
+    target_host = m.Remote("user@target.host", ["--ssh", "target-opt"], None)
+    build_host = m.Remote("user@build.host", ["--ssh", "build-opt"], None)
+
     n.copy_closure(closure, target_host)
     mock_run.assert_called_with(
-        ["nix-copy-closure", "--to", "user@host", closure],
-        extra_env={"NIX_SSHOPTS": "--ssh opt"},
+        ["nix-copy-closure", "--to", "user@target.host", closure],
+        extra_env={"NIX_SSHOPTS": "--ssh target-opt"},
+        remote=None,
+    )
+
+    n.copy_closure(closure, None, build_host)
+    mock_run.assert_called_with(
+        ["nix-copy-closure", "--from", "user@build.host", closure],
+        extra_env={"NIX_SSHOPTS": "--ssh build-opt"},
+        remote=None,
+    )
+
+    n.copy_closure(closure, target_host, build_host)
+    mock_run.assert_called_with(
+        ["nix-copy-closure", "--to", "user@target.host", closure],
+        extra_env={"NIX_SSHOPTS": "--ssh target-opt"},
+        remote=build_host,
     )