paw compatibility + minor improv.

[swfsql]

I had an error to use this library in combination with structopt + paw, so I added paw as an optional dependency behind a feature.
Also added a minor improvement for Verbosity::set_default.

[epage]

I had an error to use this library in combination with structopt + paw, so I added paw as an optional dependency behind a feature.

How does having a paw dependency fix our support for paw?

[swfsql]

I added one demonstration as a new commentary, and I'm also now repeating what I placed in there, but I think that this is the case because on how structopt macros references paw.

[matthiasbeyer]

These patches do not change anything.

Sorry to say, but I'd reject this.

[swfsql]

I admit that this is surprising, but it does make a difference.
I made a repo to demonstrate this; you can check it by running:

git clone https://github.com/swfsql/clap-comp-example.git
cd clap-comp-example

git checkout afce9fd
cargo check

git checkout 89594fe
cargo check

git diff afce9fd

The main is just:

#[derive(structopt::StructOpt)]
struct Args {
    #[structopt(flatten)]
    verbose: clap_verbosity_flag::Verbosity,
}
#[paw::main]
fn main(args: Args) {}

The initial Cargo.toml is:

[package]
name = "example-a"
version = "0.1.0"
authors = ["Thi <swfsql@gmail.com.br>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
paw = "1.0.0"
structopt = { version = "0.3.0", features = ["paw"] }

[dependencies.clap-verbosity-flag]
version = "0.3.1"

(which fails to compile)

The final Cargo.toml is:

[package]
name = "example-a"
version = "0.1.0"
authors = ["Thi <swfsql@gmail.com.br>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
paw = "1.0.0"
structopt = { version = "0.3.0", features = ["paw"] }

[dependencies.clap-verbosity-flag]
version = "0.3.1"
features = ["paw-compatibility"]

[patch.crates-io.clap-verbosity-flag]
git = "https://github.com/swfsql/clap-verbosity-flag"
rev = "d9f92b7"

(which compiles), where in this I patched it to use the one from this PR.

I think that this is the case because on how structopt macros references paw.

[epage]

Providing the error is helpful

error[E0433]: failed to resolve: use of undeclared type or module `paw`
  --> /Users/edpage/.cargo/registry/src/github.com-1ecc6299db9ec823/clap-verbosity-flag-0.3.1/src/lib.rs:21:10
   |
21 | #[derive(structopt::StructOpt, Debug, Clone)]
   |          ^^^^^^^^^^^^^^^^^^^^ use of undeclared type or module `paw`

error: aborting due to previous erro

So structopt has been configured with paw but when processing the macro within clap-verbosity-flag, it only has visibility to the dependencies of clap-verbosity-flag.

Personally, I wish macros had an option to run as if they were coming from their own crate because they make it easy to break abstractions, like here. Either structopt needs to re-export paw like they do clap or every random structopt crate has to be aware of paw and provide a feature to satisfy the dependency.

Created an issue over at TeXitoi/structopt#407

[swfsql]

I see! Thanks for creating the issue for them.