The largest organizational change is that methods used to generate the help are
implemented by the Help object and not the App, FlagBuilder, Parser, etc.
The new code is based heavily on the old one with a few minor modifications
aimed to reduce code duplication and coupling between the Help and the rest
of the code.
The new code turn things around: instead of having a HelpWriter that holds an
AnyArg object and a method that is called with a writer as argument,
there is a Help Object that holds a writer and a method that is called with a
writer as an argument.
There are still things to do such as moving `create_usage` outside the Parser.
The peformance has been affected, probably by the use of Trait Objects. This
was done as a way to reduce code duplication (i.e. in the unified help code).
This performance hit should not affect the usability as generating and printing
the help is dominated by user interaction and IO.
The old code to generate the help is still functional and is the active one.
The new code has been tested against the old one by generating help strings
for most of the examples in the repo.
`write_nspaces` has three differences with `write_spaces`
1. Accepts arguments with attribute access (such as self.writer)
2. The order of the arguments is swapped to make the writer the first
argument as in other write related macros.
3. Does not use the `write!` macro under the hood but rather calls
directly `write`
I have chosen to put the function under a new name to avoid backwards
compatibility problem but it might be better to migrate everything to
`write_nspaces` (and maybe rename it `write_spaces`)
Writing the help requires read only access to Parser's flags, opts
and positionals. This commit provides 3 functions returning iterators
over those collections (`iter_*`) allowing to have function outside
the parser to generate the help.
This commit introduces a new trait (`DispOrder`) with a single function
(`fn disp_order(&self) -> usize`). It is use to expose the display order
of an argument in a read-only manner.
Use ::std::result::Result to make macro hygienic.
I ran into an error using
```
struct Error {}
pub type Result<T> = ::std::result::Result<T, Error>;
arg_enum!{
....
}
~~~
Attached is a fix.
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Passing empty values, such as `--feature ""` now stores the empty string
correctly as a value (assuming empty values are allowed as per the arg
configuration)
Closes#470
Now if the terminal size is too small to properly wrap the help text
lines, it will default to just wrapping normalling as it should.
This is determined on a per help text basis, so because the terminal
size is too small for a single argument's help to wrap properly, all
other arguments will still wrap and align correctly. Only the one
affected argument will not align properly.
Closes#453
