tests/functional2: move commands to own lib file

Currently the Command and CommandResult classes are mixed into the nix
fixture file.
This commit moves them out into their own lib file, to make it more
obvious that they can be used standalone for other applications too

Additionally improved documentation of said classes
and bumped log level of stdout and err on unexpected exitcodes, as it is
within an error context

Change-Id: If2d554acde86fd54f2445fc46453f06923af5fe9

tests/functional2/testlib/fixtures/nix.py

@@ -1,8 +1,5 @@
 import dataclasses
-import json
-import logging
 import os
-import subprocess
 from functools import partialmethod
 from pathlib import Path
 from typing import Any, AnyStr
@@ -10,63 +7,7 @@ from collections.abc import Callable, Generator
 
 import pytest
 
-from functional2.testlib.terminal_code_eater import eat_terminal_codes
-
-
-logger = logging.getLogger(__name__)
-
-
-@dataclasses.dataclass
-class CommandResult:
-    cmd: list[str]
-    rc: int
-    """Return code"""
-    stderr: bytes
-    """Outputted stderr"""
-    stdout: bytes
-    """Outputted stdout"""
-
-    def ok(self) -> "CommandResult":
-        if self.rc != 0:
-            logger.debug("stdout: %s", self.stderr_s)
-            logger.debug("stderr: %s", self.stderr_s)
-            raise subprocess.CalledProcessError(
-                returncode=self.rc, cmd=self.cmd, stderr=self.stderr, output=self.stdout
-            )
-        return self
-
-    def expect(self, rc: int) -> "CommandResult":
-        if self.rc != rc:
-            logger.debug("stdout: %s", self.stderr_s)
-            logger.debug("stderr: %s", self.stderr_s)
-            raise subprocess.CalledProcessError(
-                returncode=self.rc, cmd=self.cmd, stderr=self.stderr, output=self.stdout
-            )
-        return self
-
-    @property
-    def stdout_s(self) -> str:
-        """Command stdout as str"""
-        return self.stdout.decode("utf-8", errors="replace")
-
-    @property
-    def stderr_s(self) -> str:
-        """Command stderr as str"""
-        return self.stderr.decode("utf-8", errors="replace")
-
-    @property
-    def stdout_plain(self) -> str:
-        """Command stderr as str with terminal escape sequences eaten and whitespace stripped"""
-        return eat_terminal_codes(self.stdout).decode("utf-8", errors="replace").strip()
-
-    @property
-    def stderr_plain(self) -> str:
-        """Command stderr as str with terminal escape sequences eaten and whitespace stripped"""
-        return eat_terminal_codes(self.stderr).decode("utf-8", errors="replace").strip()
-
-    def json(self) -> Any:
-        self.ok()
-        return json.loads(self.stdout)
+from functional2.testlib.commands import CommandResult, Command
 
 
 @dataclasses.dataclass
@@ -123,35 +64,6 @@ class NixSettings:
         return ret
 
 
-@dataclasses.dataclass
-class Command:
-    argv: list[str]
-    env: dict[str, str] = dataclasses.field(default_factory=dict)
-    stdin: bytes | None = None
-    cwd: Path | None = None
-
-    def with_env(self, **kwargs) -> "Command":
-        self.env.update(kwargs)
-        return self
-
-    def with_stdin(self, stdin: bytes) -> "Command":
-        self.stdin = stdin
-        return self
-
-    def run(self) -> CommandResult:
-        proc = subprocess.Popen(
-            self.argv,
-            stdout=subprocess.PIPE,
-            stderr=subprocess.PIPE,
-            stdin=subprocess.PIPE if self.stdin else subprocess.DEVNULL,
-            cwd=self.cwd,
-            env=self.env,
-        )
-        (stdout, stderr) = proc.communicate(input=self.stdin)
-        rc = proc.returncode
-        return CommandResult(cmd=self.argv, rc=rc, stdout=stdout, stderr=stderr)
-
-
 @dataclasses.dataclass
 class NixCommand(Command):
     settings: NixSettings = dataclasses.field(default_factory=NixSettings)