nixos-rebuild-ng: silence reexec messages

Right now reexec is really verbose when it fails: let's say the
configuration has a eval error, you will see the evaluation error twice,
once in during the reexec and another one when the configuration is
evaluated.

This commit changes this behavior so the evaluation done during re-exec
process is silent. It is still possible to check the error with `--debug` flag.

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

@@ -13,7 +13,9 @@ from .models import Action, BuildAttr, Flake, ImageVariants, NRError, Profile
 from .process import Remote, cleanup_ssh
 from .utils import Args, LogFormatter, tabulate
 
-logger: Final = logging.getLogger()
+NIXOS_REBUILD_ATTR: Final = "config.system.build.nixos-rebuild"
+
+logger: Final = logging.getLogger(__name__)
 logger.setLevel(logging.INFO)
 
 
@@ -276,26 +278,28 @@ def reexec(
     flake_build_flags: Args,
 ) -> None:
     drv = None
-    attr = "config.system.build.nixos-rebuild"
     try:
         # Parsing the args here but ignore ask_sudo_password since it is not
         # needed and we would end up asking sudo password twice
         if flake := Flake.from_arg(args.flake, Remote.from_arg(args.target_host, None)):
             drv = nix.build_flake(
-                attr,
+                NIXOS_REBUILD_ATTR,
                 flake,
                 flake_build_flags | {"no_link": True},
+                quiet=True,
             )
         else:
             build_attr = BuildAttr.from_arg(args.attr, args.file)
             drv = nix.build(
-                attr,
+                NIXOS_REBUILD_ATTR,
                 build_attr,
                 build_flags | {"no_out_link": True},
+                quiet=True,
             )
     except CalledProcessError:
         logger.warning(
-            "could not build a newer version of nixos-rebuild, using current version"
+            "could not build a newer version of nixos-rebuild, using current version",
+            exc_info=logger.isEnabledFor(logging.DEBUG),
         )
 
     if drv:
@@ -319,9 +323,9 @@ def reexec(
                 # - Exec format error (e.g.: another OS/CPU arch)
                 logger.warning(
                     "could not re-exec in a newer version of nixos-rebuild, "
-                    + "using current version"
+                    + "using current version",
+                    exc_info=logger.isEnabledFor(logging.DEBUG),
                 )
-                logger.debug("re-exec exception", exc_info=True)
                 # We already run clean-up, let's re-exec in the current version
                 # to avoid issues
                 os.execve(current, argv, os.environ | {"_NIXOS_REBUILD_REEXEC": "1"})

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

@@ -51,6 +51,7 @@ def build(
     attr: str,
     build_attr: BuildAttr,
     build_flags: Args | None = None,
+    quiet: bool = False,
 ) -> Path:
     """Build NixOS attribute using classic Nix.
 
@@ -63,7 +64,7 @@ def build(
         build_attr.to_attr(attr),
         *dict_to_flags(build_flags),
     ]
-    r = run_wrapper(run_args, stdout=PIPE)
+    r = run_wrapper(run_args, stdout=PIPE, stderr=PIPE if quiet else None)
     return Path(r.stdout.strip())
 
 
@@ -71,6 +72,7 @@ def build_flake(
     attr: str,
     flake: Flake,
     flake_build_flags: Args | None = None,
+    quiet: bool = False,
 ) -> Path:
     """Build NixOS attribute using Flakes.
 
@@ -84,7 +86,7 @@ def build_flake(
         flake.to_attr(attr),
         *dict_to_flags(flake_build_flags),
     ]
-    r = run_wrapper(run_args, stdout=PIPE)
+    r = run_wrapper(run_args, stdout=PIPE, stderr=PIPE if quiet else None)
     return Path(r.stdout.strip())
 
 

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

@@ -140,9 +140,10 @@ def test_reexec(mock_build: Mock, mock_execve: Mock, monkeypatch: MonkeyPatch) -
     mock_build.assert_has_calls(
         [
             call(
-                "config.system.build.nixos-rebuild",
+                nr.NIXOS_REBUILD_ATTR,
                 nr.models.BuildAttr(ANY, ANY),
                 {"build": True, "no_out_link": True},
+                quiet=True,
             )
         ]
     )
@@ -187,6 +188,7 @@ def test_reexec_flake(
         "config.system.build.nixos-rebuild",
         nr.models.Flake(ANY, ANY),
         {"flake": True, "no_link": True},
+        quiet=True,
     )
     # do not exec if there is no new version
     mock_execve.assert_not_called()
@@ -266,6 +268,7 @@ def test_execute_nix_boot(mock_run: Mock, tmp_path: Path) -> None:
                 ],
                 check=True,
                 stdout=PIPE,
+                stderr=None,
                 **DEFAULT_RUN_KWARGS,
             ),
             call(
@@ -340,6 +343,7 @@ def test_execute_nix_build_vm(mock_run: Mock, tmp_path: Path) -> None:
                 ],
                 check=True,
                 stdout=PIPE,
+                stderr=None,
                 **DEFAULT_RUN_KWARGS,
             )
         ]
@@ -404,6 +408,7 @@ def test_execute_nix_build_image_flake(mock_run: Mock, tmp_path: Path) -> None:
                 ],
                 check=True,
                 stdout=PIPE,
+                stderr=None,
                 **DEFAULT_RUN_KWARGS,
             ),
             call(
@@ -471,6 +476,7 @@ def test_execute_nix_switch_flake(mock_run: Mock, tmp_path: Path) -> None:
                 ],
                 check=True,
                 stdout=PIPE,
+                stderr=None,
                 **DEFAULT_RUN_KWARGS,
             ),
             call(
@@ -761,6 +767,7 @@ def test_execute_nix_switch_flake_target_host(
                 ],
                 check=True,
                 stdout=PIPE,
+                stderr=None,
                 **DEFAULT_RUN_KWARGS,
             ),
             call(
@@ -1028,6 +1035,7 @@ def test_execute_build(mock_run: Mock, tmp_path: Path) -> None:
                 ],
                 check=True,
                 stdout=PIPE,
+                stderr=None,
                 **DEFAULT_RUN_KWARGS,
             )
         ]
@@ -1067,6 +1075,7 @@ def test_execute_test_flake(mock_run: Mock, tmp_path: Path) -> None:
                 ],
                 check=True,
                 stdout=PIPE,
+                stderr=None,
                 **DEFAULT_RUN_KWARGS,
             ),
             call(

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

@@ -36,14 +36,18 @@ def test_build(mock_run: Mock) -> None:
             "foo",
         ],
         stdout=PIPE,
+        stderr=None,
     )
 
     assert n.build(
-        "config.system.build.attr", m.BuildAttr(Path("file"), "preAttr")
+        "config.system.build.attr",
+        m.BuildAttr(Path("file"), "preAttr"),
+        quiet=True,
     ) == Path("/path/to/file")
     mock_run.assert_called_with(
         ["nix-build", Path("file"), "--attr", "preAttr.config.system.build.attr"],
         stdout=PIPE,
+        stderr=PIPE,
     )
 
 
@@ -74,6 +78,26 @@ def test_build_flake(mock_run: Mock, monkeypatch: MonkeyPatch, tmpdir: Path) ->
             "foo",
         ],
         stdout=PIPE,
+        stderr=None,
+    )
+
+    assert n.build_flake(
+        "config.system.build.toplevel",
+        flake,
+        None,
+        quiet=True,
+    ) == Path("/path/to/file")
+    mock_run.assert_called_with(
+        [
+            "nix",
+            "--extra-experimental-features",
+            "nix-command flakes",
+            "build",
+            "--print-out-paths",
+            '.#nixosConfigurations."hostname".config.system.build.toplevel',
+        ],
+        stdout=PIPE,
+        stderr=PIPE,
     )