config: inline parse_setoption

It only makes the code harder to understand in my opinion.

Also remove the manual `setattr(option, name, value)` which are unneeded
because `parse` already updates the `Namespace`.

Author: bluetech

src/_pytest/config/__init__.py

@@ -56,6 +56,7 @@
 from _pytest._io import TerminalWriter
 from _pytest.compat import assert_never
 from _pytest.config.argparsing import Argument
+from _pytest.config.argparsing import FILE_OR_DIR
 from _pytest.config.argparsing import Parser
 import _pytest.deprecated
 import _pytest.hookspec
@@ -1538,13 +1539,11 @@ def parse(self, args: list[str], addopts: bool = True) -> None:
         self._preparse(args, addopts=addopts)
         self._parser.after_preparse = True  # type: ignore
         try:
-            args = self._parser.parse_setoption(
-                args, self.option, namespace=self.option
-            )
+            parsed = self._parser.parse(args, namespace=self.option)
         except PrintHelp:
             return
         self.args, self.args_source = self._decide_args(
-            args=args,
+            args=getattr(parsed, FILE_OR_DIR),
             pyargs=self.known_args_namespace.pyargs,
             testpaths=self.getini("testpaths"),
             invocation_dir=self.invocation_params.dir,

src/_pytest/config/argparsing.py

@@ -7,7 +7,6 @@
 from collections.abc import Sequence
 import os
 from typing import Any
-from typing import cast
 from typing import final
 from typing import Literal
 from typing import NoReturn
@@ -134,17 +133,6 @@ def _getparser(self) -> PytestArgumentParser:
         file_or_dir_arg.completer = filescompleter  # type: ignore
         return optparser
 
-    def parse_setoption(
-        self,
-        args: Sequence[str | os.PathLike[str]],
-        option: argparse.Namespace,
-        namespace: argparse.Namespace | None = None,
-    ) -> list[str]:
-        parsedoption = self.parse(args, namespace=namespace)
-        for name, value in parsedoption.__dict__.items():
-            setattr(option, name, value)
-        return cast(list[str], getattr(parsedoption, FILE_OR_DIR))
-
     def parse_known_args(
         self,
         args: Sequence[str | os.PathLike[str]],

testing/test_parseopt.py

@@ -158,19 +158,16 @@ def test_parse_will_set_default(self, parser: parseopt.Parser) -> None:
         parser.addoption("--hello", dest="hello", default="x", action="store")
         option = parser.parse([])
         assert option.hello == "x"
-        del option.hello
-        parser.parse_setoption([], option)
-        assert option.hello == "x"
 
-    def test_parse_setoption(self, parser: parseopt.Parser) -> None:
+    def test_parse_set_options(self, parser: parseopt.Parser) -> None:
         parser.addoption("--hello", dest="hello", action="store")
         parser.addoption("--world", dest="world", default=42)
 
         option = argparse.Namespace()
-        args = parser.parse_setoption(["--hello", "world"], option)
+        parser.parse(["--hello", "world"], option)
         assert option.hello == "world"
         assert option.world == 42
-        assert not args
+        assert getattr(option, parseopt.FILE_OR_DIR) == []
 
     def test_parse_special_destination(self, parser: parseopt.Parser) -> None:
         parser.addoption("--ultimate-answer", type=int)