Support flags with values in native completions

[epage]

See #3166 for more context

• code
• tests

Tasks

• feat(clap_complete): Support flags with values --flag barand -f bar in native completions #5539
• feat(clap_complete): Support -fbar and -f=bar in native completions #5576
• Deal with COMP_WORDBREAKS

[epage]

We currently support

• --foo=bar, see

  clap/clap_complete/src/dynamic/completer.rs

  Lines 106 to 124 in 4aefa3c

  	if let Some((flag, value)) = arg.to_long() {
  	if let Ok(flag) = flag {
  	if let Some(value) = value {
  	if let Some(arg) = cmd.get_arguments().find(|a| a.get_long() == Some(flag)) {
  	completions.extend(
  	complete_arg_value(value.to_str().ok_or(value), arg, current_dir)
  	.into_iter()
  	.map(|(os, help)| {
  	// HACK: Need better `OsStr` manipulation
  	(format!("--{}={}", flag, os.to_string_lossy()).into(), help)
  	}),
  	);
  	}
  	} else {
  	completions.extend(longs_and_visible_aliases(cmd).into_iter().filter_map(
  	|(f, help)| f.starts_with(flag).then(|| (format!("--{f}").into(), help)),
  	));
  	}
  	}

• bar, see

  clap/clap_complete/src/dynamic/completer.rs

  Lines 150 to 155 in 4aefa3c

  	if let Some(positional) = cmd
  	.get_positionals()
  	.find(|p| p.get_index() == Some(pos_index))
  	{
  	completions.extend(complete_arg_value(arg.to_value(), positional, current_dir));
  	}

We need to also support

• -f=bar
• -f bar
• --foo bar
• -fbar

Relevant code in the main parser

clap/clap_builder/src/parser/parser.rs

Line 179 in 4aefa3c

} else if let Some(short_arg) = arg_os.to_short() {

clap/clap_builder/src/parser/parser.rs

Lines 939 to 957 in 4aefa3c

	// Check for trailing concatenated value
	//
	// Cloning the iterator, so we rollback if it isn't there.
	let val = short_arg.clone().next_value_os().unwrap_or_default();
	debug!("Parser::parse_short_arg:iter:{c}: val={val:?}, short_arg={short_arg:?}");
	let val = Some(val).filter(|v| !v.is_empty());
	// Default to "we're expecting a value later".
	//
	// If attached value is not consumed, we may have more short
	// flags to parse, continue.
	//
	// e.g. `-xvf`, when require_equals && x.min_vals == 0, we don't
	// consume the `vf`, even if it's provided as value.
	let (val, has_eq) = if let Some(val) = val.and_then(|v| v.strip_prefix("=")) {
	(Some(val), true)
	} else {
	(val, false)
	};

See also

• https://docs.rs/clap_lex/latest/clap_lex/struct.ShortFlags.html

[HKalbasi]

I would like to take this.

[epage]

Shan is going to be taking this.