Re: guile-config: Command --help is not displayed when there are required arguments

[Alex Sassmannshausen]

Hi  Sirgazil,

sirgazil <address@hidden> writes:

> Hi,
>
> When using "guile-config" for declaring my CLIs I've noticed that if I
> define an argument as non-optional for a command, then trying to
> display the --help of that command fails.

You are correct.  This issue arises because guile-config uses (ice-9
getopt-long) internally to parse the command line arguments and handle
all the usual gnu cli argument niceties.

However this causes a chicken and egg problem: to execute help when the
--help flag is provide we need to have parsed the cli options.  But
getopt-long throws an error whilst parsing the cli options as soon as it
detects a mandatory argument is missing.

This is not ideal.  The solution would probably be have to be to
re-implement cli argument parsing outside of getopt-long, or to patch
getopt-long to not throw on validation-error but to return an
error-structure, which includes the parsed cli args, but also any
problems it encountered during validation.

Dunno which is better at this point, but I'll log your report and my
thoughts as a bug against guile-config for now.

Of course, patches implementing either solution, welcome! :-)

Best wishes,

Alex

>
> Consider the following script which displays "What yummy apple!" when it's 
> run like "$ eat apple":
>
>
> #+BEGIN_SRC scheme
> (use-modules (config)
>              (config api)
>              (ice-9 format)
>              (ice-9 match))
>
>
> ;;; CONSTANTS
> ;;; =========
>
> (define FRUITS
>   (list "apple" "banana" "kiwi" "mango"))
>
>
>
> ;;; VALIDATORS
> ;;; ==========
>
> (define (fruit? fruit)
>   (member fruit FRUITS))
>
>
>
> ;;; ARGUMENTS AND OPTIONS
> ;;; =====================
>
> (define fruit
>   (argument (name 'fruit)
>             (synopsis "The name of a fruit.")
>             (example "apple")
>             (optional? #false)
>             (test fruit?)))
>
>
>
> ;;; CLI SPECIFICATION
> ;;; =================
>
> (define spec
>   (configuration
>    (name 'eat)
>    (synopsis "Eat imaginary fruits.")
>    (version "1.0")
>    (arguments (list fruit))))
>
>
>
> ;;; CLI DISPATCHER
> ;;; ==============
>
> (define (dispatcher command spec)
>   #| Execute the appropriate procedure for the given COMMAND if it is
>   part of the given command-line interface specification.
>
>   COMMAND (list of strings)
>     A list of strings that represent a command-line instruction passed
>     to the program (see the Guile command-line procedure).
>
>   SPEC (Configuration)
>     A <configuration> record as specified by the guile-config library
>     specifying the command-line interface of the program.
>
>   RESULT
>     Execute the COMMAND or display help information if the COMMAND is
>     not recognized. |#
>   (let* ((options (getopt-config-auto command spec))
>          (fruit (option-ref options '(fruit))))
>     (catch 'match-error
>       (lambda ()
>         (match (full-command options)
>           ((_) (format #true "What yummy ~a!!~%" fruit))))
>
>       (lambda (. args)
>         (begin (display "ERROR: Command not found.")
>                (newline) (newline)
>                (emit-help options))))))
>
>
>
> ;;; RUN
> ;;; ===
>
> (dispatcher (command-line) spec)
>
> #+END_SRC
>
>
> Now, when I try to display the help information of the "eat" command, I get 
> this message:
>
>
> #+BEGIN_EXAMPLE
> $ eat --help
> error: eat: argument must be specified: fruit
> Usage: eat 
>
> Options:
> #+END_EXAMPLE
>
>
> Is this a bug or am I doing something wrong?
>
>
> ---
> https://sirgazil.bitbucket.io/