How to use app_from_crate! in clap_app!

[xaocon]

Clap version

2.33.3 - though I checked masters docstrings and I don't see any improvement.

Where

clap/src/macros.rs

Line 169 in 3907e11

/// Allows you to build the `App` instance from your Cargo.toml at compile time.

https://docs.rs/clap/2.33.3/clap/macro.app_from_crate.html

What's wrong

It's not clear how to develop this into a fully formed app. I was hoping to use it like clap_app! but with sections removed that had already been filled but that didn't work. I tried chaining them a couple of different ways. I tried using the result from app_from_crate! as the first argument to clap_app! but none of that works. Macros in Macros don't seem to work anywhere as I originally tried using the crate_*! macros to fill in clap_app!. I'm not sure there is a good way to set up options if you use app_from_crate! but it doesn't seem like it's a very helpful macro if not.

How to fix

I'm not really sure. If someone could explain it to me I wouldn't mind putting in a PR for it but I don't have enough understanding of macros to make sense of it currently.

[pksunkara]

Here's an example,

clap/tests/app_from_crate.rs

Line 16 in 6ce1e4f

fn app_from_crate() {

And the macro code is pretty self-explanatory.

clap/src/macros.rs

Line 194 in 3907e11

macro_rules! app_from_crate {

[xaocon]

The app_from_crate! code is pretty self-explanatory but I had hoped to use app_from_crate! with the argument building style from clap_app! and I can't make sense of that one. I guess you're saying that there's not a good way to build out arguments for the app using macros if you use app_from_crate!? It turns out I had had a mistake in my syntax that was keeping me from using the crate_*! macros in clap_app! so it's not really much of a big deal to just use clap_app!.

If there is some reasonable way to use the macro arguments from clap_app! with app_from_crate! then I think it would be helpful mention it in the documents as I believe it wasn't completely unreasonable for me to think that was possible. If there is, I think it would be helpful to show how in the example. In either case, I'd be happy to open a PR for it. I also noticed a small typo in the crate_license! macro docs that I could correct at the same time.

[pksunkara]

Can you paste your code?

[pksunkara]

And no, app_from_crate! cannot be used with clap_app

[xaocon]

This is what it looks like now. It works but I'll probably try to tweak a little.

		let matches = clap_app!(myapp =>
			(version: crate_version!())
			(author: crate_authors!())
			(about: crate_description!())
			(@arg output: -o --output [DIR] "Output directory (defaults to working directory)")
			(@arg cafile: -c --cafile [File] "Alternative CA file to use")
			(@arg dryrun: -d --dryrun "Don't actually download files")
			(@arg URL: +required "Sets the input file to use")
		).get_matches();

I had hoped to do something like:

		let matches = app_from_crate!(
			(@arg output: -o --output [DIR] "Output directory (defaults to working directory)")
			(@arg cafile: -c --cafile [File] "Alternative CA file to use")
			(@arg dryrun: -d --dryrun "Don't actually download files")
			(@arg URL: +required "Sets the input file to use")
		).get_matches();

or maybe

		let matches = clap_app!(myapp =>
			app_from_crate!()
			(@arg output: -o --output [DIR] "Output directory (defaults to working directory)")
			(@arg cafile: -c --cafile [File] "Alternative CA file to use")
			(@arg dryrun: -d --dryrun "Don't actually download files")
			(@arg URL: +required "Sets the input file to use")
		).get_matches();

but I couldn't see how that would work. I couldn't see the usefulness of app_from_crate! if it doesn't provide a helpful way to add args so I thought I was missing something. I only thought it might be helpful to add some clarity to the docs.

This is the typo I was talking about

clap/src/macros.rs

Line 47 in 3907e11

/// .version(crate_license!())

[pksunkara]

Fixed the typo, but your first code example is the only way to do it.

[xaocon]

Sounds good. I wasn't really hoping for you to make them work that way. Just thought it might be worth mentioning one way or another in the app_from_crate! macro docs. Thanks for the help!