Support ArgumentDefaultsHelpFormatter by allowing extra calls to default_factory #70
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Still check that default_factory takes effect called at parsing time, but allow additional calls to default_factory in order to initialize argparse option default This breaks if default_factory has side-effects but that is an extremely bad idea. It's much more useful to support ArgumentDefaultsHelpFormatter instead.
…elds with dataclass-level defaults This prevents argparse from assigning the argparse-level default. This ensures that any default_factory is always called at parsing time instead of parser-creation time.
This is an explicit test for the expected behavior in issue mivade#32
…t_factory treatment
…ult_factory behavior change
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Fixes issues #32 and #65
ArgumentDefaultsHelpFormatter is currently broke because argparse_dataclass always passes a default value of
dataclasses.MISSINGto argparse. This is done in order to ensure that when default_factory is used it is only called exactly once at parse time.Relax this behavior to allow an additional call to default_factory at parser creation time so that defaults are properly visible. This can break when default_factory has side-effects but that would be a very bad practice.
It is still guaranteed that default_factory() is called for each new parse so something like
default_factory=dt.datetime.nowworks exactly as expected.This is implemented by initializing an argparse.Namespace before parsing which fills in all fields which have dataclass-level default values. This prevents argparse from assigning the argparse-level default and ensures that default_factory is called for a fresh result each parse.