Passing default/override arguments via the environment

[MoSal]

So, I wanted to add this feature to one of my tools. I didn't find a way to do it with clap alone. So I looked around. Found shlex, adapted it to work with OsStr/OsString types.

Then, getting all arguments including defaults/overrides via the environment is as simple as:

use std::env;
use shlex_os::ShlexOs;

// ...

impl Config {
    fn all_args() -> Vec<OsString> {
        let mut cmd_args = env::args_os();
        let bin = cmd_args.next()
          .expect("impossible no bin");
        let pre_str = env::var_os("SOMETOOL_PRE_ARGS")
          .unwrap_or_default();
        let post_str = env::var_os("SOMETOOL_POST_ARGS")
          .unwrap_or_default();
        [bin].into_iter()
            .chain(ShlexOs::new(pre_str))
            .chain(cmd_args)
            .chain(ShlexOs::new(post_str))
            .collect()
    }
    // ....
}

Did I go about this the right way, or did I miss something?

[epage]

Overall the approach seems fine and is similar to what is done for argfile. Doing this more generally and in clap would require resolving some issues around subcommands and anything else related to the similar #2836

FYI shlex would be easy to update to work on bytes which hopefully could then be made to work with os_str_bytes: comex/rust-shlex#12

[MoSal]

FYI shlex would be easy to update to work on bytes which hopefully could then be made to work with os_str_bytes: comex/rust-shlex#12

Would that look different than what I already done in my fork!

[epage]

1. My main point is that shlex is open to expanding support
2. I was only looking at supporting bytes at the shlex level and worrying about OsStr above it to keep the change minimal