cmds.projects.CmdCreateFile: Fix --format help

The possible values of --format are defined by an Enum which is never
really used as such. Derive them from class introspection instead, i.e.
offer all formats that have a corresponding render_<format>() name.

Also, turn the option into real argparse-backed choices, and make the
argument mandatory, because that reflects the reality of the implementation
- there is no default.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/cmds/projects/CmdCreateFile.py

@@ -1,8 +1,12 @@
+from __future__ import annotations
+
 import sys
 
 from argparse import ArgumentParser, ArgumentTypeError, Namespace
-from enum import Enum, auto
-from typing import override
+from typing import TYPE_CHECKING, override
+
+if TYPE_CHECKING:
+    from typing import Iterable
 
 from ...lib.log import WARNING, log
 from ...lib.version.base import Syntax
@@ -17,10 +21,6 @@ def key_value(s: str) -> tuple[str, str]:
         raise ArgumentTypeError('Expected KEY=VALUE')
     return key, value
 
-# TODO: Put the more elaborate stuff into lib
-class Fmt(Enum):
-    Pyright = auto()
-
 class CmdCreateFile(Cmd):  # export
 
     def __jw_required(
@@ -50,6 +50,11 @@ class CmdCreateFile(Cmd):  # export
             ret = [module, *ret]
         return ret
 
+    @property
+    def __format_choices(self) -> Iterable[str]:
+        p = 'render_'
+        return [name.removeprefix(p) for name in dir(self) if name.startswith(p)]
+
     def __render(
         self,
         template_name: str,
@@ -100,12 +105,12 @@ class CmdCreateFile(Cmd):  # export
     @override
     def add_arguments(self, parser: ArgumentParser) -> None:
         super().add_arguments(parser)
+        format_choices = self.__format_choices
         parser.add_argument(
             '--format',
-            help = (
-                'Output format, for example: '
-                ', '.join([fmt.name.lower() for fmt in Fmt])
-            )
+            choices = format_choices,
+            required = True,
+            help = 'Output format, one of: ' + ', '.join(format_choices)
         )
         parser.add_argument(
             '--search-path',
@@ -132,6 +137,6 @@ class CmdCreateFile(Cmd):  # export
     @override
     async def _run(self, args: Namespace) -> None:
         method = getattr(self, 'render_' + args.format, None)
-        if method is None:  # Should be prevented by choices=[] but keeps linter happy
+        if method is None:  # choices already restricts this; keeps the linter happy
             raise Exception(f'Unsupported output format {args.format}')
         sys.stdout.write(method(args.module, args.field))