import dataclasses import sys from functools import partialmethod from pathlib import Path from textwrap import dedent from typing import Any, Literal from collections.abc import Callable, Generator import pytest from functional2.testlib.fixtures.command import CommandResult, Command from functional2.testlib.fixtures.env import ManagedEnv from functional2.testlib.utils import is_value_of_type @dataclasses.dataclass class NixSettings: """Settings for invoking Nix""" experimental_features: set[str] | None = None store: str | None = None """ The store to operate on (may be a path or other thing, see `nix help-stores`). Note that this can be set to the test's store directory if you want to use /nix/store paths inside that test rather than NIX_STORE_DIR renaming /nix/store to some unstable name (assuming that no builds are invoked). """ nix_store_dir: Path | None = None """ Alternative name to use for /nix/store: breaks all references and NAR imports if set, but does allow builds in tests (since builds do not require chroots if the store is relocated). """ def feature(self, *names: str) -> "NixSettings": """ Adds the given features to the list of enabled `experimental_features` :param names: feature names to enable :return: self, command is chainable """ self.experimental_features = (self.experimental_features or set()) | set(names) return self def to_config(self, env: ManagedEnv) -> str: config = dedent(f""" show-trace = true sandbox = true # explicitly disable substitution by default, otherwise we may attempt to contact # substituters and slow down many tests with pointless connection retry timeouts. substituters = extra-sandbox-paths = {" ".join(env.path.to_sandbox_paths())} """) # Note: newline at the end is required due to nix being nix; # FIXME(Jade): #953 this is annoying in the CLI too, we should fix it! def serialise(value: Any) -> str: # TODO(Commentator2.0): why exactly are ints supported? if is_value_of_type(value, set[str | int]): return " ".join(serialise(e) for e in value) if is_value_of_type(value, str | int): return str(value) msg = f"Value is unsupported in nix config: {value!r}, must bei either `str|int` or `set[str|int]`" raise ValueError(msg) def field_may(name: str, value: Any, serializer: Callable[[Any], str] = serialise): nonlocal config if value is not None: config += f"{name} = {serializer(value)}\n" field_may("experimental-features", self.experimental_features) field_may("store", self.store) assert self.store or self.nix_store_dir, ( "Failing to set either nix_store_dir or store will cause accidental use of the system store." ) return config def to_env_overlay(self, env: ManagedEnv) -> None: cfg = self.to_config(env) (env.dirs.nix_conf_dir / "nix.conf").write_text(cfg) env.set_env("NIX_CONFIG", cfg) if self.nix_store_dir: env.dirs.nix_store_dir = str(self.nix_store_dir) @dataclasses.dataclass class Nix: env: ManagedEnv _settings: NixSettings | None = dataclasses.field(init=False, default=None) @property def settings(self) -> NixSettings: """ :return: the settings for the nix instance """ if self._settings is None: self._settings = NixSettings() self._settings.store = f"local?root={self.env.dirs.test_root}&store=/nix/store" return self._settings def nix_cmd( self, argv: list[str], flake: bool = False, build: bool | Literal["auto"] = "auto" ) -> Command: """ Constructs a NixCommand with the appropriate settings. :param build: if the executed command wants to build stuff. This is required due to darwin shenanigans. "auto" will try to autodetect, override using `True` or `False`. Has no effect on linux. """ # Create a copy of settings to not have a writing side effect settings = dataclasses.replace(self.settings) if flake: settings.feature("nix-command", "flakes") # FIXME(Commentator2.0): Darwin needs special handling here, as it does not support (non-root) chroots... # Hence, it cannot build using a relocated store so we just use the local (aka global) store instead # This is kinda ugly but what else can one do if sys.platform == "darwin": if build is True or ( # argv[1:2] does not throw a key error on empty lists # hence not crashing this check on an empty `nix.nix([])` call build == "auto" and (argv[0] == "nix-build" or argv[1:2] == ["build"]) ): settings.store = None settings.nix_store_dir = self.env.dirs.nix_store_dir settings.to_env_overlay(self.env) return Command(argv=argv, _env=self.env) def nix( self, cmd: list[str], nix_exe: str = "nix", flake: bool = False, build: bool | Literal["auto"] = "auto", ) -> Command: return self.nix_cmd([nix_exe, *cmd], flake=flake, build=build) # Mark each of these as correct as they are not ClassVars, but we also don't want to turn off RUF045 nix_build = partialmethod(nix, nix_exe="nix-build") # noqa: RUF045 nix_shell = partialmethod(nix, nix_exe="nix-shell") # noqa: RUF045 nix_store = partialmethod(nix, nix_exe="nix-store") # noqa: RUF045 nix_env = partialmethod(nix, nix_exe="nix-env") # noqa: RUF045 nix_instantiate = partialmethod(nix, nix_exe="nix-instantiate") # noqa: RUF045 nix_channel = partialmethod(nix, nix_exe="nix-channel") # noqa: RUF045 nix_prefetch_url = partialmethod(nix, nix_exe="nix-prefetch-url") # noqa: RUF045 def eval(self, expr: str, settings: NixSettings | None = None) -> CommandResult: """ calls `nix eval --json --expr {expr}` using the given expression :param expr: what to evaluate :param settings: if none, the global settings will be used, otherwise the given one :return: result of the evaluation """ orig = dataclasses.replace(self.settings) self._settings = settings or self.settings self.settings.feature("nix-command") cmd = self.nix(["eval", "--json", "--expr", expr]) # restore previous settings self._settings = orig return cmd.run() @property def store_dir(self) -> Path: """ The actual NIX_STORE_DIR this Nix command uses. """ assert self.env.dirs.nix_store_dir is not None, "bug in ManagedEnv" return self.env.dirs.nix_store_dir def physical_store_path_for(self, path: str | Path) -> Path: """ Takes a /nix/store/… path and rewrites it to be relative to this Nix's NIX_STORE_DIR. Nix accepts and returns store paths as `/nix/store` even when that's not where `NIX_STORE_DIR` physically is on the filesystem. Since we move the conceptual root for Nix to `test_root`, these "virtual" paths differ from the physical ones. So this function will convert `/nix/store` "virtual" paths to their real, physical location on the system. Basically, if you're passing it to `nix build` or `nix-store` or whatever, you want the `/nix/store` version. If you're passing it to a Python API (like pathlib.Path.exists()) or a command that operates on arbitrary files instead of store paths, you want the output of this function. :param path: a string or Path to convert :return: a Path object holding the rewritten, physical system path to the store entry """ return Path(str(path).replace("/nix/store", self.store_dir.as_posix())) def hash_path(self, store_path: str | Path, *args: str) -> str: """ Shortcut to use `nix hash path {store_path}`, converting "virtual" store paths returned from Nix to their physical system paths including the test root. :param store_path: store path of the derivation or entry to hash """ actual_path = self.physical_store_path_for(store_path).as_posix() res = self.nix(["hash", "path", actual_path, *args], flake=True).run().ok() return res.stdout_plain @pytest.fixture def nix(tmp_path: Path, env: ManagedEnv) -> Generator[Nix, Any, None]: """ Provides a rich way of calling `nix`. For pre-applied commands use `nix.nix_instantiate`, `nix.nix_build` etc. After configuring the command, use `.run()` to run it """ yield Nix(env) # when things are done using the nix store, the permissions for the store are read only # after the test was executed, we set the permissions to rwx (write being the important part) # for pytest to be able to delete the files during cleanup cmd = Command(argv=["chmod", "-R", "+w", str(tmp_path.absolute())], _env=env) cmd.run().ok()