fix(parser): Provide default value for Actions #3786
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Actions were inspired by Python and Python does not implicitly default any field when an action is given. From a Builder API perspective, this seemed fine because we tend to focus the Builder API on giving the user all information so they can make their own decisions. When working on the Derive API, this became a problem because users were going to have to migrate from an implied default to an explicit default when a common default is good enough most of the time. This shouldn't interfere with Builder users getting more details when needed. This also highlighted two problems - We set the index for defaults - We don't debug_assert when applying conditional requirements with a default present
epage
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Jun 6, 2022
This is the derive support for clap-rs#3774 (see also clap-rs#3775, clap-rs#3777) This combined with `value_parser` replaces `parser`. The main frustration with this is that `ArgAction::Count` (the replacement for `parse(from_occurrences)` must be a `u64`. We could come up with a magic attribute that is meant to be the value parser's parsed type. We could then use `TryFrom` to convert the parsed type to the user's type to allow more. That is an exercise for the future. Alternatively, we have clap-rs#3792. Prep for this included - clap-rs#3782 - clap-rs#3783 - clap-rs#3786 - clap-rs#3789 - clap-rs#3793
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Actions were inspired by Python and Python does not implicitly default
any field when an action is given. From a Builder API perspective, this
seemed fine because we tend to focus the Builder API on giving the user
all information so they can make their own decisions. When working on
the Derive API, this became a problem because users were going to have
to migrate from an implied default to an explicit default when a common
default is good enough most of the time. This shouldn't interfere with
Builder users getting more details when needed.
This also highlighted two problems
default present