proj/pkgcore/snakeoil:master commit in: src/snakeoil/cli/, /, tests/cli/

commit:     a831aed3e017109f85502cf877f58d42937b7ef9
Author:     Arthur Zamarin <arthurzam <AT> gentoo <DOT> org>
AuthorDate: Sat Aug  8 06:10:42 2026 +0000
Commit:     Arthur Zamarin <arthurzam <AT> gentoo <DOT> org>
CommitDate: Sat Aug  8 06:10:42 2026 +0000
URL:        https://gitweb.gentoo.org/proj/pkgcore/snakeoil.git/commit/?id=a831aed3

arghparse: accept space-separated option values starting with a dash

Stock argparse classifies any prefixed token that doesn't match a known
option (e.g. "-VisibilityCheck") as an unknown optional, so an option
expecting a value refuses to consume the following token and fails with
"expected one argument" unless the "--opt=value" form is used.

Override ArgumentParser._parse_optional to reclassify such single-dash
unknown tokens as plain values, which is exactly what the csv_negations
and csv_elements actions expect ("-Foo", "+Foo"). Double-dash tokens are
left untouched so genuine option typos ("--typo") keep reporting as
unrecognized arguments.

Resolves: https://github.com/pkgcore/snakeoil/issues/97
Signed-off-by: Arthur Zamarin <arthurzam <AT> gentoo.org>

 NEWS.rst                      |  5 +++++
 src/snakeoil/cli/arghparse.py | 22 +++++++++++++++++++---
 tests/cli/test_arghparse.py   | 17 +++++++++++++++--
 3 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/NEWS.rst b/NEWS.rst
index 556a36d..abcd9f0 100644
--- a/NEWS.rst
+++ b/NEWS.rst
@@ -5,6 +5,11 @@ Release Notes
 snakeoil 0.11.4 (unreleased)
 ----------------------------
 
+- ``snakeoil.cli.arghparse.ArgumentParser``: options now accept space-separated
+  values that start with a single dash (e.g. ``--checks -VisibilityCheck``),
+  matching the previously required ``--checks=-VisibilityCheck`` form.  Unknown
+  ``--`` options keep reporting as unrecognized arguments (Arthur Zamarin, #97)
+
 - ``snakeoil.dist.generate_man_rsts``: fix man page generation failing under
   Python 3.14 with ``TypeError: 'str' object cannot be interpreted as an
   integer``, caused by ``functools.partial`` becoming a method descriptor

diff --git a/src/snakeoil/cli/arghparse.py b/src/snakeoil/cli/arghparse.py
index cd872f1..e5ff3e3 100644
--- a/src/snakeoil/cli/arghparse.py
+++ b/src/snakeoil/cli/arghparse.py
@@ -1224,6 +1224,22 @@ class ArgumentParser(OptionalsParser, CsvActionsParser):
                 for subcmd in subcmd_modules:
                     subparsers.add_command(subcmd)
 
+    def _parse_optional(self, arg_string):
+        """Treat unknown single-dash tokens as values rather than options."""
+        result = super()._parse_optional(arg_string)
+        if result is None:
+            return result
+        option_tuples = result if isinstance(result, list) else [result]
+        # the "unknown optional" fallthrough is a lone tuple whose action is None
+        if (
+            len(option_tuples) == 1
+            and option_tuples[0][0] is None
+            and len(arg_string) >= 2
+            and arg_string[1] not in self.prefix_chars
+        ):
+            return None
+        return result
+
     def _update_desc(self, description=None, docs=None):
         """Extract the description to use.
 
@@ -1516,7 +1532,7 @@ def existent_path(value):
         raise argparse.ArgumentTypeError(f"nonexistent path: {value!r}")
     try:
         return os.path.realpath(value)
-    except EnvironmentError as e:
+    except OSError as e:
         raise ValueError(
             f"while resolving path {value!r}, encountered error: {e}"
         ) from e
@@ -1530,7 +1546,7 @@ def existent_dir(value):
         raise argparse.ArgumentTypeError(f"file already exists: {value!r}")
     try:
         return os.path.realpath(value)
-    except EnvironmentError as e:
+    except OSError as e:
         raise ValueError(
             f"while resolving path {value!r}, encountered error: {e}"
         ) from e
@@ -1543,7 +1559,7 @@ def create_dir(value):
         os.makedirs(path, exist_ok=True)
     except FileExistsError:
         raise argparse.ArgumentTypeError(f"file already exists: {value!r}")
-    except IOError as e:
+    except OSError as e:
         raise argparse.ArgumentTypeError(f"failed creating dir: {e}")
     return path
 

diff --git a/tests/cli/test_arghparse.py b/tests/cli/test_arghparse.py
index 63d37ae..a3c5e71 100644
--- a/tests/cli/test_arghparse.py
+++ b/tests/cli/test_arghparse.py
@@ -201,8 +201,21 @@ class TestArgumentParser(TestCsvActionsParser, TestOptionalsParser):
                     arghparse.ArgumentParser(quiet=True, verbose=True)
                 )
                 namespace = parser.parse_args(args)
-                assert parser.verbosity == val, "{} failed".format(args)
-                assert namespace.verbosity == val, "{} failed".format(args)
+                assert parser.verbosity == val, f"{args} failed"
+                assert namespace.verbosity == val, f"{args} failed"
+
+    def test_dashed_value(self):
+        # options should accept space-separated values starting with a single dash
+        parser = argparse_helpers.mangle_parser(arghparse.ArgumentParser())
+        parser.add_argument("-c", "--checks", action="csv_negations")
+
+        for args in (["--checks", "-a,b"], ["-c", "-a,b"], ["--checks=-a,b"]):
+            namespace = parser.parse_args(args)
+            assert namespace.checks == (["a"], ["b"]), f"{args} failed"
+
+        # unknown double-dash options are still reported as errors
+        with pytest.raises(argparse_helpers.Error):
+            parser.parse_args(["--typo"])
 
     def test_verbosity_disabled(self):
         parser = argparse_helpers.mangle_parser(