options: fix typing of add_to_argparse

Which wants a string, but then passes that string to a function that
wants an OptionKey, which means that we'll always miss the lookup in
BULITIN_DIR_NOPREFIX_OPTIONS, and return the default. The only case this
gets used we cast an OptionKey to str, and then pass that. So instead,
do the cast inside the function when necessary and pass the OptionKey

mesonbuild/coredata.py

@@ -857,10 +857,10 @@ def save(obj: CoreData, build_dir: str) -> str:
 
 def register_builtin_arguments(parser: argparse.ArgumentParser) -> None:
     for n, b in options.BUILTIN_OPTIONS.items():
-        b.add_to_argparse(str(n), parser, '')
+        b.add_to_argparse(n, parser, '')
     for n, b in options.BUILTIN_OPTIONS_PER_MACHINE.items():
-        b.add_to_argparse(str(n), parser, ' (just for host machine)')
-        b.add_to_argparse(str(n.as_build()), parser, ' (just for build machine)')
+        b.add_to_argparse(n, parser, ' (just for host machine)')
+        b.add_to_argparse(n.as_build(), parser, ' (just for build machine)')
     parser.add_argument('-D', action='append', dest='projectoptions', default=[], metavar="option",
                         help='Set the value of an option, can be used several times to set multiple options.')
 

mesonbuild/options.py

@@ -588,7 +588,7 @@ def prefixed_default(self, name: 'OptionKey', prefix: str = '') -> T.Any:
             pass
         return self.default
 
-    def add_to_argparse(self, name: str, parser: argparse.ArgumentParser, help_suffix: str) -> None:
+    def add_to_argparse(self, name: OptionKey, parser: argparse.ArgumentParser, help_suffix: str) -> None:
         kwargs: ArgparseKWs = {}
 
         c = self._argparse_choices()
@@ -601,9 +601,9 @@ def add_to_argparse(self, name: str, parser: argparse.ArgumentParser, help_suffi
         if c and not b:
             kwargs['choices'] = c
         kwargs['default'] = argparse.SUPPRESS
-        kwargs['dest'] = name
+        kwargs['dest'] = str(name)
 
-        cmdline_name = self.argparse_name_to_arg(name)
+        cmdline_name = self.argparse_name_to_arg(str(name))
         parser.add_argument(cmdline_name, help=h + help_suffix, **kwargs)