fix: Only show_default on --*/--no-* pair bool arguments for the ac…

…tual default.

CHANGELOG.md

@@ -15,6 +15,7 @@ s.
 - feat: User defined parsers can access the `TypeView` by accepting it as an argument.
 - feat: Add new API for defining subcommands as methods.
 - feat: Add Arg.show_default option to optionally avoid displaying default in help text.
+- fix: Only show_default on `--*/--no-*` pair bool arguments for the actual default.
 
 ## 0.23
 

src/cappa/arg.py

@@ -621,11 +621,18 @@ def explode_negated_bool_args(args: typing.Sequence[Arg]) -> typing.Iterable[Arg
             positives = [item for item in long if "--no-" not in item]
             if negatives and positives:
                 positive_arg = dataclasses.replace(
-                    arg, long=positives, action=ArgAction.store_true
+                    arg,
+                    long=positives,
+                    action=ArgAction.store_true,
+                    show_default=arg.default is True,
                 )
                 negative_arg = dataclasses.replace(
-                    arg, long=negatives, action=ArgAction.store_false
+                    arg,
+                    long=negatives,
+                    action=ArgAction.store_false,
+                    show_default=arg.default is False,
                 )
+
                 yield positive_arg
                 yield negative_arg
                 yielded = True

tests/arg/test_show_default.py

@@ -0,0 +1,71 @@
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+import pytest
+from typing_extensions import Annotated
+
+import cappa
+from tests.utils import TestOutput, backends, parse
+
+
+@backends
+def test_show_default_default_true(backend, capsys):
+    @dataclass
+    class Command:
+        foo: bool = False
+
+    assert parse(Command, backend=backend).foo is False
+
+    with pytest.raises(cappa.HelpExit):
+        parse(Command, "--help", backend=backend)
+
+    output = TestOutput.from_capsys(capsys)
+    assert "(Default: False)" in output.stdout
+
+
+@backends
+def test_show_default_set_false(backend, capsys):
+    @dataclass
+    class Command:
+        foo: Annotated[bool, cappa.Arg(show_default=False)] = False
+
+    assert parse(Command, backend=backend).foo is False
+
+    with pytest.raises(cappa.HelpExit):
+        parse(Command, "--help", backend=backend)
+
+    output = TestOutput.from_capsys(capsys)
+    assert "(Default: False)" not in output.stdout
+
+
+@backends
+def test_show_default_no_option_shows_for_false_default(backend, capsys):
+    @dataclass
+    class Command:
+        foo: Annotated[bool, cappa.Arg(long="--foo/--no-foo")] = False
+
+    assert parse(Command, backend=backend).foo is False
+
+    with pytest.raises(cappa.HelpExit):
+        parse(Command, "--help", backend=backend)
+
+    stdout = TestOutput.from_capsys(capsys).stdout.replace(" ", "")
+    assert "[--foo](Default:True)" not in stdout
+    assert "[--no-foo](Default:False)" in stdout
+
+
+@backends
+def test_show_default_no_option_shows_for_true_default(backend, capsys):
+    @dataclass
+    class Command:
+        foo: Annotated[bool, cappa.Arg(long="--foo/--no-foo")] = True
+
+    assert parse(Command, backend=backend).foo is True
+
+    with pytest.raises(cappa.HelpExit):
+        parse(Command, "--help", backend=backend)
+
+    stdout = TestOutput.from_capsys(capsys).stdout.replace(" ", "")
+    assert "[--foo](Default:True)" in stdout
+    assert "[--no-foo](Default:False)" not in stdout

tests/utils.py

@@ -1,4 +1,5 @@
 import contextlib
+from dataclasses import dataclass
 from typing import Union
 from unittest.mock import patch
 
@@ -57,3 +58,17 @@ def ignore_docstring_parser(monkeypatch):
 
 def strip_trailing_whitespace(text):
     return "\n".join([line.rstrip() for line in text.split("\n")])
+
+
+@dataclass
+class TestOutput:
+    stdout: str
+    stderr: str
+
+    @classmethod
+    def from_capsys(cls, capsys):
+        outerr = capsys.readouterr()
+
+        out = strip_trailing_whitespace(outerr.out)
+        err = strip_trailing_whitespace(outerr.err)
+        return cls(out, err)