Before:
- `bool`: a flag
- `Option<_>`: not required
- `Option<Option<_>>` is not required and when it is present, the value
is not required
- `Vec<_>`: multiple values, optional
- `Option<Vec<_>>`: multiple values, min values of 0, optional
After:
- `bool`: a flag
- `Option<_>`: not required
- `Option<Option<_>>` is not required and when it is present, the value
is not required
- `Vec<_>`: multiple occurrences, optional
- optional: `Vec` implies 0 or more, so should not imply required
- `Option<Vec<_>>`: multiple occurrences, optional
- optional: Use over `Vec` to detect when no option being present when
using multiple values
Motivations:
My priorities were:
1. Are we getting in the users way?
2. Does the API make sense?
3. Does the API encourage best practices?
I was originally concerned about the lack of composability with
`Option<Option<_>>` and `Option<Vec<_>>` (and eventually `Vec<Vec<_>>`).
It prescribes special meaning to each type depending on where it shows
up, rather than providing a single meaning for a type generally. You
then can't do things like have `Option<_>` mean "required argument with
optional value" without hand constructing it. However, in practice the
outer type correlates with the argument occurrence and the inner type
with the value. It is rare to want the value behavior without also the
occurrence behavior. So I figure it is probably fine as long as people
can set the flags to manually get the behavior they want.
`Vec<_>` implies multiple occurrences, rather than multiple values.
Anecdotally, whenever I've used the old `Arg::multiple`, I thought I was
getting `Arg::multiple_occurrences` only. `Arg::multiple_values`,
without any bounds or delimiter requirement, can lead to a confusing
user experience and isn't a good default for these. On top of that, if
someone does have an unbounded or a delimiter multiple values, they are
probably also using multiple occurrences.
`Vec<_>` is optional because a `Vec` implies 0 or more, so we stick to
the meaning of the rust type. At least for me, I also rarely need a
required with multiple occurrences argument but more often need optional
with multiple occurrences.
`Option<Vec<_>>` ends up matching `Vec<_>` which can raise the question
of why have it. Some users might prefer the type. Otherwise, this is
so users can detect whether the argument is present or not when using
`min_values(0)`. Rather than defining an entire policy around this and
having users customize it, or setting `min_values(0)` without the rest
of a default policy, this gives people a blank slate to work from.
Another design option would have been to not infer any special-type
settings if someone sets a handful of settings manually, which would
have avoided the confusion in Issue clap-rs/clap 2599 but I see that
being confusing (for someone who knows the default, they will be
expecting it to be additive; which flags disable inferred settings?) and
brittle (as flags are added or changed, how do we ensure we keep this
up?).
Tests were added to ensure we support people customizing the behavior to
match their needs.
This is not solving:
- `Vec<Vec<_>>`, see clap-rs/clap 2924
- `(T1, T2)`, `Vec<(T1, T2)>`, etc, see clap-rs/clap 1717
- `Vec<Option<_>>` and many other potential combinations
Fixes clap-rs/clap 1772
Fixes clap-rs/clap 2599
See also clap-rs/clap 2195
In #27, we removed some default features. When doing so, some places
weren't updated but `doc` feature covered it ... except it was only
partially updated. This makes sure we test all the features.
This both distances itself from our 'require' terminology and aligns
itself with `Option::expect`, making it more likely for people to guess
the intended behavior.
This makes it easier for us to compose. Before, we had to infer things
like "bold" based on the color. Now we just say "error" and get all of
the formatting specific to that.
Too many times people have to disable default features. Let's try to
have a more minimal out of box experience.
- `derive`: people are already used to adding this feature for serde
- `cargo`: not needed for derive
- `env`: most probably don't use this
- `unicode`: most CLIs are probably ASCII. We should do a debug warn
about this though
BREAKING CHANGE: `derive`, `cargo`, `env`, and `unicode` are no longer
on by default.
This ports our example testing over to [trycmd](https://docs.rs/) so
we can:
- More thoroughly test our examples
- Provide always-up-to-date example usage
The old way of testing automatically picked up examples. This new way
requires we have a `.md` file that uses the example in some way.
Notes:
- Moved overall example description to the `.md` file
- I added cross-linking between related examples
- `14_groups` had a redundant paragraph (twice talked about "one and
only one"
This is intended to replace the runtime usage parser and is not meant to
be a complete API in of itself, like `clap_app!`. What is in scope is
everything that visually makes sense as in a usage string (see
[docopt](http://docopt.org/) for inspiration). General setting of
attributes is out of scope.
This deviates from both `clap_app` and the runtime usage parser
- `clap_app` supported multiple values but has a bug because we made
`Arg::value_name` non-appending, so we aren't supporting this yet
- We do not yet support optional flags that take a value
- In both, `...` is multiple occurrences and values while its only
multiple occurrences for us
- We explicitly support optional values for flags
- Unlike `clap_app`, our name is optional
- Unlike runtime usage parser, our name syntax is simpler
- Unlike runtime usage parser, our name syntax does not allow modifiers
Its more limited than I would like. Hopefully some people better with
macros can expand the feature set and turn more runtime errors into
compile-time errors.
This is to prepare for deprecating the runtime usage parser (#8).
