👽️ Ensure compatibility with Click 8.3.0 by restoring the original value_is_missing function

typer/core.py

@@ -403,6 +403,9 @@ def make_metavar(self, ctx: Union[click.Context, None] = None) -> str:
             var += "..."
         return var
 
+    def value_is_missing(self, value: Any) -> bool:
+        return _value_is_missing(self, value)
+
 
 class TyperOption(click.core.Option):
     def __init__(
@@ -593,6 +596,23 @@ def _write_opts(opts: Sequence[str]) -> str:
 
         return ("; " if any_prefix_is_slash else " / ").join(rv), help
 
+    def value_is_missing(self, value: Any) -> bool:
+        return _value_is_missing(self, value)
+
+
+def _value_is_missing(param: click.Parameter, value: Any) -> bool:
+    if value is None:
+        return True
+
+    # Click 8.3 and beyond
+    # if value is UNSET:
+    #     return True
+
+    if (param.nargs != 1 or param.multiple) and value == ():
+        return True  # pragma: no cover
+
+    return False
+
 
 def _typer_format_options(
     self: click.core.Command, *, ctx: click.Context, formatter: click.HelpFormatter