ignore extra macos parameter

[sixcorners]

When you start an app on macos it will sometimes pass a process serial number. This blows up apps that use clap.
The place where it is getting passed for me is from the "App downloaded from the internet" dialog box. When you click open it will try to open the rust app but fail and do nothing. If you ignored a parameter that looks like this -psn_0_5539144 on macos then this would be fixed for all apps using clap.

Rust Version

rustc 1.39.0

Affected Version of clap

whatever the latest is (v2.31.2)

Expected Behavior Summary

App doesn't fail when running from the "App downloaded from the internet" dialog box.

Actual Behavior Summary

"error: Found argument '-p' which wasn't expected, or isn't valid in this context"

Steps to Reproduce the issue

Launch a rust application on macos from the "App downloaded from the internet" warning dialog box.

[nixpulvis]

IMO, this is a tragic interface being forced upon the community by Apple. Why should argument parsers need to deal with this, or applications without a need for the PSN. Couldn't it be passed in the ENV much more transparently?

Either way it seems many applications don't care about this PSN, for example:

https://github.com/bitcoin/bitcoin/blob/b6e34afe9735faf97d6be7a90fafd33ec18c0cbb/src/util/system.cpp#L383-L389

So adding an option to ignore it on macOS may make sense. I wouldn't want non-macOS code to need to care though.

[chrisduerr]

If this was ignored in clap directly, I also think that it probably shouldn't just be done automatically without any compile-time checks. If a user wants to add their own -psn flag, things shouldn't explode.

Though I don't think it's possible to build the string -psn_ as option right now, so that should be fine. But blocking just -psn would certainly cause huge troubles.

[woelper]

I had this issue, too - in case it helps anyone, i used .get_matches_from() and filtered incoming arguments before with let args: Vec<String> = std::env::args().filter(|a| !a.contains("psn_")).collect();