Support non-Unix options (e.g. find -exec, bash +O shopt, cmd.exe /c, gcc -Wl,)

[mkayaalp]

Child Tasks:

• Support alternative name/value separator #3026
• Support for single hyphen in long arguments #1210 (if we generalize it to this case)

Please complete the following tasks

• I have searched the discussions
• I have searched the existing issues

Describe your use case

There are many CLIs that do not follow the Unix way of short vs. long options. While it might not be a good idea for new programs to have such an interface, it may be needed for compatibility.

Examples

1. Long option with a single hyphen-minus (-) instead of a double hyphen-minus (--)

The examples are probably too many to count, as this is very common. From the output of find --help:

      -ilname PATTERN -iname PATTERN -inum N -iwholename PATTERN -iregex PATTERN
      -links N -lname PATTERN -mmin N -mtime N -name PATTERN -newer FILE

From the output of gcc --help:

  -dumpspecs               Display all of the built in spec strings.
  -dumpversion             Display the version of the compiler.
  -dumpmachine             Display the compiler's target processor.

From the output of ld --help:

  -rpath PATH                 Set runtime shared library search path
  -rpath-link PATH            Set link time shared library search path
  -shared, -Bshareable        Create a shared library
  -pie, --pic-executable      Create a position independent executable

From the output of qemu-system-x86_64 --help

-serial dev     redirect the serial port to char device 'dev'
-parallel dev   redirect the parallel port to char device 'dev'
-monitor dev    redirect the monitor to char device 'dev'

2. Long option with a single plus (+) instead of a double hyphen-minus (--)

I'm sure there are others, but I can point to the output of Xwayland --help for this:

+xinerama              Enable XINERAMA extension
-xinerama              Disable XINERAMA extension
...
+extension name        Enable extension
-extension name        Disable extension

3. Short option with a plus (+) instead of a hyphen-minus (-)

In this case it is a short option because it can be combined as +OO opt1 opt2. Although the value needs to be separated with a space: +Oopt1 does not work. From man 1 bash:

       [-+]O [shopt_option]
                 shopt_option  is  one  of  the  shell options accepted by the
                 shopt  builtin  (see  SHELL  BUILTIN  COMMANDS  below).    If
                 shopt_option is present, -O sets the value of that option; +O
                 unsets it.  If shopt_option is not supplied,  the  names  and
                 values  of the shell options accepted by shopt are printed on
                 the standard output.  If the invocation  option  is  +O,  the
                 output is displayed in a format that may be reused as input.

4. No space between option and value

As in short options, but the option is not a single character, so combining is not possible. From gcc --help:

  -Wa,<options>            Pass comma-separated <options> on to the assembler.
  -Wp,<options>            Pass comma-separated <options> on to the preprocessor.
  -Wl,<options>            Pass comma-separated <options> on to the linker.

(I guess it looks like W is the short option and the first value a/p/l signifies assembler, preprocessor, or linker. But combining such short options would not make sense.)

5. Long option with value after equals (=), but without the double hyphen-minus (--)

From dd --help

  count=N         copy only N input blocks
  ibs=BYTES       read up to BYTES bytes at a time (default: 512)
  if=FILE         read from FILE instead of stdin
  iflag=FLAGS     read as per the comma separated symbol list
  obs=BYTES       write BYTES bytes at a time (default: 512)
  of=FILE         write to FILE instead of stdout
  oflag=FLAGS     write as per the comma separated symbol list

6. Windows way: slash (/) instead of double hyphen-minus (--) and colon (:) instead of equals (=)

Not very familiar with Windows command line parameters, but from examples it seems only long options, mostly single-letter, are used. They are still "long" options since there is no combining. Option values are separated by a space or a colon (:). Also, /? is the equivalent of -h, --help.

cmd [/c|/k] [/s] [/q] [/d] [/a|/u] [/t:{<b><f> | <f>}] [/e:{on | off}] [/f:{on | off}] [/v:{on | off}] [<string>]

icacls <filename> [/grant[:r] <sid>:<perm>[...]] [/deny <sid>:<perm>[...]] [/remove[:g|:d]] <sid>[...]] [/t] [/c] [/l] [/q] [/setintegritylevel <Level>:<policy>[...]]

pathping [/n] [/h <maximumhops>] [/g <hostlist>] [/p <Period>] [/q <numqueries> [/w <timeout>] [/i <IPaddress>] [/4 <IPv4>] [/6 <IPv6>][<targetname>]

winnt32 [/checkupgradeonly] [/cmd: <CommandLine>] [/cmdcons] [/copydir:{i386|ia64}\<FolderName>] [/copysource: <FolderName>] [/debug[<Level>]:[ <FileName>]] [/dudisable] [/duprepare: <pathName>] [/dushare: <pathName>] [/emsport:{com1|com2|usebiossettings|off}] [/emsbaudrate: <BaudRate>] [/m: <FolderName>]  [/makelocalsource] [/noreboot] [/s: <Sourcepath>] [/syspart: <DriveLetter>] [/tempdrive: <DriveLetter>] [/udf: <ID>[,<UDB_File>]] [/unattend[<Num>]:[ <AnswerFile>]]

Describe the solution you'd like

Instead of (or in addition to) specifying short vs. long, maybe we could specify:

• The prefix: "-", "--", "/", "+", ""
• Whether to combine as in short options or not
• Whether to allow, or require, or disallow space between the option name and its value
• The separator between the option name and its value(s): "=", ":"

Alternatives, if applicable

No response

Additional Context

No response

[epage]

My comment in #1210 speaks of a general solution that would cover the wider case than just single hyphens in long arguments.

Whether to allow, or require, or disallow space between the option name and its value

We do have requires_equals, granted that only switches between allow space vs disallow and doesn't cover require space.

It doesn't allow a different separator value. We'd need to create a name, add support for it, and deprecate the existing function (since it name references the syntax and not the general semantics). We'd end up with a pair like use_delimiter and value_delimiter.

[epage]

I broke the name/value separator part out into a child task

[mkayaalp]

Thank you for looking into this.

We do have requires_equals, granted that only switches between allow space vs disallow and doesn't cover require space.

Since creating this issue, I looked at CLI guidelines of POSIX, GNU, Solaris and realized that handling of space in clap for optional option-arguments is not the Unix way: #3030

[Burning1020]

Excuse me, when will we support for the single hyphen feature? Is there any PR working on it?

[epage]

Work to be done for this:

1. Implementing clap_lex Done
2. Creating a trait for it that is object safe (not started)
3. Modify clap::Command so it accepts an alternative clap_lex implementation

When doing these, we need to balance

• Performance
• Compile time and binary size for the default case
• API compatibility
  • the trait needs to be defined somewhere that has the same API guarantees as clap
  • clap_lex does not yet have those guarantees. I would rather not have os_str_bytes in the API either

However, this is not a high priority for me but the 4.x issues are.