From 6de0b62e5df761cf48c7c5b8077f5306997fc2bd Mon Sep 17 00:00:00 2001
From: DanCardin <ddcardin@gmail.com>
Date: Mon, 16 Sep 2024 17:58:56 -0400
Subject: [PATCH] fix: Only apply `--no-*` handling when there is both a
 positive and negative variant.

---
 CHANGELOG.md           |  2 ++
 pyproject.toml         |  2 +-
 src/cappa/arg.py       | 21 +++++++++++----------
 src/cappa/argparse.py  | 16 ----------------
 src/cappa/parser.py    | 15 ++++++++-------
 tests/arg/test_bool.py | 26 ++++++++++++++++++++++++++
 6 files changed, 48 insertions(+), 34 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6f8cacc..d652b1c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,8 @@
 ### 0.22.5
 
 - fix: Refactor parser combinators into dedicated module, and document the behavior more thoroughly.
+- refactor: Pull handling of `--no-*` bool arguments out of the parser
+- fix: Only apply `--no-*` handling when there is both a positive and negative variant
 
 ### 0.22.4
 
diff --git a/pyproject.toml b/pyproject.toml
index 6e17220..d5f228b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [project]
 name = "cappa"
-version = "0.22.4"
+version = "0.22.5"
 description = "Declarative CLI argument parser."
 
 urls = {repository = "https://github.com/dancardin/cappa"}
diff --git a/src/cappa/arg.py b/src/cappa/arg.py
index 4c58f4f..8be2dac 100644
--- a/src/cappa/arg.py
+++ b/src/cappa/arg.py
@@ -619,19 +619,20 @@ def explode_negated_bool_args(args: typing.Sequence[Arg]) -> typing.Iterable[Arg
     for arg in args:
         yielded = False
         if isinstance(arg.action, ArgAction) and arg.action.is_bool_action and arg.long:
-            long = typing.cast(list[str], arg.long)
+            long = typing.cast(typing.List[str], arg.long)
 
             negatives = [item for item in long if "--no-" in item]
             positives = [item for item in long if "--no-" not in item]
-            positive_arg = dataclasses.replace(
-                arg, long=positives, action=ArgAction.store_true
-            )
-            negative_arg = dataclasses.replace(
-                arg, long=negatives, action=ArgAction.store_false
-            )
-            yield positive_arg
-            yield negative_arg
-            yielded = True
+            if negatives and positives:
+                positive_arg = dataclasses.replace(
+                    arg, long=positives, action=ArgAction.store_true
+                )
+                negative_arg = dataclasses.replace(
+                    arg, long=negatives, action=ArgAction.store_false
+                )
+                yield positive_arg
+                yield negative_arg
+                yielded = True
 
         if not yielded:
             yield arg
diff --git a/src/cappa/argparse.py b/src/cappa/argparse.py
index c6b2eb0..1adb9b2 100644
--- a/src/cappa/argparse.py
+++ b/src/cappa/argparse.py
@@ -93,22 +93,6 @@ def print_help(self, file=None):
         raise HelpExit(self.command.help_formatter(self.command, self.prog))
 
 
-class BooleanOptionalAction(argparse.Action):
-    """Simplified backport of same-named class from 3.9 onward.
-
-    We know more about the called context here, and thus need much less of the
-    logic. Also, we support 3.8, which does not have the original class, so we
-    couldn't use it anyway.
-    """
-
-    def __init__(self, **kwargs):
-        super().__init__(nargs=0, **kwargs)
-
-    def __call__(self, parser, namespace, values, option_string=None):
-        assert isinstance(option_string, str)
-        setattr(namespace, self.dest, not option_string.startswith("--no-"))
-
-
 def custom_action(arg: Arg, action: Callable):
     class CustomAction(argparse.Action):
         def __call__(  # type: ignore
diff --git a/src/cappa/parser.py b/src/cappa/parser.py
index 325d0af..b94fdcd 100644
--- a/src/cappa/parser.py
+++ b/src/cappa/parser.py
@@ -624,11 +624,12 @@ class Value(typing.Generic[T]):
     value: T
 
 
-def store_bool(val: bool):
-    def store():
-        return val
+def store_true():
+    return True
 
-    return store
+
+def store_false():
+    return False
 
 
 def store_count(context: ParseContext, arg: Arg):
@@ -645,13 +646,13 @@ def store_append(context: ParseContext, arg: Arg, value: Value[typing.Any]):
     return result
 
 
-process_options = {
+process_options: dict[ArgAction, typing.Callable] = {
     ArgAction.help: HelpAction.from_context,
     ArgAction.version: VersionAction.from_arg,
     ArgAction.completion: CompletionAction.from_value,
     ArgAction.set: store_set,
-    ArgAction.store_true: store_bool(True),
-    ArgAction.store_false: store_bool(False),
+    ArgAction.store_true: store_true,
+    ArgAction.store_false: store_false,
     ArgAction.count: store_count,
     ArgAction.append: store_append,
 }
diff --git a/tests/arg/test_bool.py b/tests/arg/test_bool.py
index 7f401de..1c83f31 100644
--- a/tests/arg/test_bool.py
+++ b/tests/arg/test_bool.py
@@ -168,3 +168,29 @@ class ArgTest:
     with patch("os.environ", new={"ENV_DEFAULT": "1"}):
         test = parse(ArgTest, "--env-default", backend=backend)
     assert test.env_default is True
+
+
+@backends
+def test_sole_no_arg(backend):
+    @dataclass
+    class ArgTest:
+        no_dry_run: bool = False
+
+    test = parse(ArgTest, backend=backend)
+    assert test.no_dry_run is False
+
+    test = parse(ArgTest, "--no-dry-run", backend=backend)
+    assert test.no_dry_run is True
+
+
+@backends
+def test_sole_no_arg_inverted(backend):
+    @dataclass
+    class ArgTest:
+        no_dry_run: bool = True
+
+    test = parse(ArgTest, backend=backend)
+    assert test.no_dry_run is True
+
+    test = parse(ArgTest, "--no-dry-run", backend=backend)
+    assert test.no_dry_run is False