Deduplicate --help option definition (pallets#2563)

Co-authored-by: Andreas Backx <[email protected]>

src/click/__init__.py

@@ -19,6 +19,7 @@
 from .decorators import confirmation_option as confirmation_option
 from .decorators import group as group
 from .decorators import help_option as help_option
+from .decorators import HelpOption as HelpOption
 from .decorators import make_pass_decorator as make_pass_decorator
 from .decorators import option as option
 from .decorators import pass_context as pass_context

src/click/core.py

@@ -1285,25 +1285,19 @@ def get_help_option_names(self, ctx: Context) -> t.List[str]:
         return list(all_names)
 
     def get_help_option(self, ctx: Context) -> t.Optional["Option"]:
-        """Returns the help option object."""
+        """Returns the help option object.
+
+        Unless ``add_help_option`` is ``False``.
+        """
         help_options = self.get_help_option_names(ctx)
 
         if not help_options or not self.add_help_option:
             return None
 
-        def show_help(ctx: Context, param: "Parameter", value: str) -> None:
-            if value and not ctx.resilient_parsing:
-                echo(ctx.get_help(), color=ctx.color)
-                ctx.exit()
-
-        return Option(
-            help_options,
-            is_flag=True,
-            is_eager=True,
-            expose_value=False,
-            callback=show_help,
-            help=_("Show this message and exit."),
-        )
+        # Avoid circular import.
+        from .decorators import HelpOption
+
+        return HelpOption(help_options)
 
     def make_parser(self, ctx: Context) -> OptionParser:
         """Creates the underlying option parser for this command."""

src/click/decorators.py

@@ -522,32 +522,41 @@ def callback(ctx: Context, param: Parameter, value: bool) -> None:
     return option(*param_decls, **kwargs)
 
 
-def help_option(*param_decls: str, **kwargs: t.Any) -> t.Callable[[FC], FC]:
-    """Add a ``--help`` option which immediately prints the help page
+class HelpOption(Option):
+    """Pre-configured ``--help`` option which immediately prints the help page
     and exits the program.
+    """
 
-    This is usually unnecessary, as the ``--help`` option is added to
-    each command automatically unless ``add_help_option=False`` is
-    passed.
+    def __init__(
+        self,
+        param_decls: t.Optional[t.Sequence[str]] = None,
+        **kwargs: t.Any,
+    ) -> None:
+        if not param_decls:
+            param_decls = ("--help",)
 
-    :param param_decls: One or more option names. Defaults to the single
-        value ``"--help"``.
-    :param kwargs: Extra arguments are passed to :func:`option`.
-    """
+        kwargs.setdefault("is_flag", True)
+        kwargs.setdefault("expose_value", False)
+        kwargs.setdefault("is_eager", True)
+        kwargs.setdefault("help", _("Show this message and exit."))
+        kwargs.setdefault("callback", self.show_help)
 
-    def callback(ctx: Context, param: Parameter, value: bool) -> None:
-        if not value or ctx.resilient_parsing:
-            return
+        super().__init__(param_decls, **kwargs)
 
-        echo(ctx.get_help(), color=ctx.color)
-        ctx.exit()
+    @staticmethod
+    def show_help(ctx: Context, param: Parameter, value: bool) -> None:
+        """Callback that print the help page on ``<stdout>`` and exits."""
+        if value and not ctx.resilient_parsing:
+            echo(ctx.get_help(), color=ctx.color)
+            ctx.exit()
 
-    if not param_decls:
-        param_decls = ("--help",)
 
-    kwargs.setdefault("is_flag", True)
-    kwargs.setdefault("expose_value", False)
-    kwargs.setdefault("is_eager", True)
-    kwargs.setdefault("help", _("Show this message and exit."))
-    kwargs["callback"] = callback
+def help_option(*param_decls: str, **kwargs: t.Any) -> t.Callable[[FC], FC]:
+    """Decorator for the pre-configured ``--help`` option defined above.
+
+    :param param_decls: One or more option names. Defaults to the single
+        value ``"--help"``.
+    :param kwargs: Extra arguments are passed to :func:`option`.
+    """
+    kwargs.setdefault("cls", HelpOption)
     return option(*param_decls, **kwargs)