Don't display defaults if the default value is None.

cyclopts/help.py

@@ -42,7 +42,7 @@ class SilentRich:
     """Dummy object that causes nothing to be printed."""
 
     def __rich_console__(self, console, options):
-        # This generator yields nothing, so 'rich' will print nothing for this object.
+        # This generator yields nothing, so ``rich`` will print nothing for this object.
         if False:
             yield
 
@@ -251,7 +251,9 @@ def is_short(s):
             if choices:
                 help_components.append(rf"[dim]\[choices: {choices}][/dim]")
 
-        if param.show_default and not is_required(parameter):
+        if not is_required(parameter) and (
+            param.show_default or (param.show_default is None and parameter.default is not None)
+        ):
             default = ""
             if isclass(type_) and issubclass(type_, Enum):
                 default = parameter.default.name.lower().replace("_", "-")

cyclopts/parameter.py

@@ -115,10 +115,11 @@ def validator(type_, value: Any) -> None:
     Defaults to ``parse`` value (``True``).
     """
 
-    show_default: bool = field(default=True)
+    show_default: Optional[bool] = field(default=None)
     """
     If a variable has a default, display the default in the help page.
-    Defaults to ``True``.
+
+    Defaults to ``None``, which is similar to ``True``, but will not display the default if it's ``None``.
     """
 
     show_choices: bool = field(default=True)

docs/source/vs_typer/help_defaults/README.rst

@@ -45,3 +45,6 @@ Cyclopts fixes this:
    # │ *  SRC,--src  File to compress. [required]                         │
    # │    DST,--dst  Path to save compressed data to. [default: out.zip]  │
    # ╰────────────────────────────────────────────────────────────────────╯
+
+Additionally, if the default value is ``None``, cyclopts's default configuration will **not** display ``[default: None]``.
+Typically ``None`` is a sentinel value who's true value gets set inside the function.

tests/test_help.py

@@ -288,7 +288,7 @@ def cmd(
     expected = dedent(
         """\
         ╭─ Parameters ───────────────────────────────────────────────────────╮
-        │ FOO,--foo,--empty-foo  Docstring for foo. [default: None]          │
+        │ FOO,--foo,--empty-foo  Docstring for foo.                          │
         ╰────────────────────────────────────────────────────────────────────╯
         """
     )