"""Arguments parsing utilities."""
import os
import argparse
[docs]class ArgMixin:
"""
Utility mixin that can be used with Enums for cmdline arg parsing.
Supports:
* 'kebab-case' <-> 'CONSTANT_NAME' conversion.
* Custom parser logic that displays
all available options on failure.
* Pretty help text rendering for each option.
(need to be used with `argparse.RawTextHelpFormatter`)
"""
[docs] @classmethod
def str_to_enum(cls, val):
"""
`my-enum` -> EnumClass.MY_ENUM
"""
try:
return cls[val.upper().replace("-", "_")]
except KeyError:
msg = "Invalid value: `{}`, available values are: {}".format(
val,
", ".join(
["`{}`".format(cls.enum_to_str(enm)) for enm in cls]
),
)
raise KeyError(msg)
[docs] @classmethod
def enum_to_str(cls, enm):
"""
EnumClass.MY_ENUM -> `my-enum`
"""
return enm.name.lower().replace("_", "-")
[docs] @classmethod
def parse(cls, arg):
"""
Get the enum for given cmdline arg in string form, display
all available options when an invalid value is parsed.
"""
try:
return cls.str_to_enum(arg).value
except KeyError as e:
raise argparse.ArgumentTypeError(str(e))
[docs] @classmethod
def get_descriptions(cls):
"""
Override this method to return a dictionary with Enums as keys
and description strings as values.
This will later on be rendered via `--help` command.
"""
return {}
[docs] @classmethod
def get_help_text(cls, default):
"""Render help text in the 'arg-value': 'description' format."""
descriptions = cls.get_descriptions()
help_strings = []
help_strings.append("(default: {})".format(default))
if descriptions:
for enm in cls:
help_strings.append(
'"{}" - {}'.format(cls.enum_to_str(enm), descriptions[enm])
)
return "\n".join(help_strings)
[docs] @classmethod
def get_parser_context(cls, default=None, **kwargs):
"""
Shortcut method for populating
`Argparse.parser.add_argument` params.
"""
return dict(
type=cls.parse,
default=default,
help=cls.get_help_text(default=default),
**kwargs
)