Adding own text to --help

[manio]

Hi.
I have the following clap code:
https://github.com/manio/aa-proxy-rs/blob/main/src/main.rs#L42
Which is leading to this result:
https://github.com/manio/aa-proxy-rs/tree/main?tab=readme-ov-file#usage

I want to ask if and how can I customize the first line with app name:
aa-proxy-rs 0.3.0
Currently in build.rs I am obtaining git revision which is then used in runtime like so:
aa-proxy-rs is starting, build: 20250419_100041, git: 20250418-4aca6bc-dirty

Can I customize the help somehow?

ps. I was looking at #460 but don't understand if and how can I use it :(

[epage]

The main way to customize it is through help_template though that doesn't work well for reporting runtime state (is starting) as you'll need to look it up even when --help isn't being used.

I'm interested in making help generation more modular, we just haven't gotten to it yet.

btw is there a reason you are still on clap v3?

[manio]

Thanks! Will look into this...

btw is there a reason you are still on clap v3?

No reason - I just copypasted the crate version from other project. Will have to upgrade it :)

[manio]

@epage
Just trying to upgrade to newest clap and got some problems:

error[E0425]: cannot find value `from_os_str` in this scope
  --> src/main.rs:70:15
   |
70 |         parse(from_os_str),
   |               ^^^^^^^^^^^ not found in this scope

error[E0425]: cannot find value `from_os_str` in this scope
  --> src/main.rs:88:24
   |
88 |     #[clap(long, parse(from_os_str), default_value = "/var/run/hostapd.conf")]
   |                        ^^^^^^^^^^^ not found in this scope

I was searching for properly migrate this code (tried try_from_str =, change PathBuf to OsString) but I stuck... what is the preferred way to parsing those file path arguments in new version?

[epage]

With clap v4, you no longer need to say how to parse a PathBuf or an OsString. We use a technique called "deref specialization" to know how to parse those specific types.

btw did you follow the migration guide at https://github.com/clap-rs/clap/blob/master/CHANGELOG.md#400---2022-09-28

[manio]

Ah, OK this in now clear, and the migration guide is what I've been missing, thanks again! :)

[manio]

@epage
Ed, Sorry for bothering again but I hope you don't mind.

I almost successfully migrated to newest clap with manio/aa-proxy-rs@dedd5da
However one single problem left. I was searching in the changelog for this but can't find anything related.
The problem is the default_missing_value here: https://github.com/manio/aa-proxy-rs/blob/main/src/main.rs#L68
It was working fine with previous clap version, but now it seems it is broken because when user pass only -c which means the default missing value with zeros has to be applied, clap is writing the error:
error: a value is required for '--connect <CONNECT>' but none was supplied

Can you help with this?
Of course it is supposed to work like this:

-c SPECIFIED_MAC_ADDRESS
-c       //here the default mac address with zeros has to be applied

[epage]

Option<Address> is treated as the whole option is not required (docs). If you want the value to be optional, then you need to specify that as well with num_args(0..=1) (docs).

[manio]

Worked, thanks again :)