Re: markup->string

[Thomas Morley]

Am So., 13. Nov. 2022 um 16:30 Uhr schrieb Jean Abou Samra <jean@abou-samra.fr>:
>
>
>
> > Le 13 nov. 2022 à 16:22, Thomas Morley <thomasmorley65@gmail.com> a écrit :
> >
> > Nevertheless, _if_ the old code is just (markup->string
> > <whatever-markup>), would it be possible to leave it untouched while
> > running convert-ly? After all it continues to work with 2.23. in this
> > simple manor, only inserting a more complex expression, if the old
> > code already has an optional argument?
> > Can't check myself, my python is as non-existent as my C++ ...
>
>
> How do you know if the old code does not use the optional argument? It could 
> be any Scheme expression, or even a #{ … #} expression. Scheme has more 
> syntax than one might think: there could be ; or #! or #| comments and all 
> sorts of things.
>
> One could special-case (markup->string <symbol>), catching a subset of those 
> cases. I’m not bothered by the current replacement, but would that make you 
> happier? In any case, we can’t reliably detect all cases of markup->string 
> applies to one argument only.
>
> Jean

Well, I have to admit I can't follow.
In my understanding the old markup->string has one or more arguments,
the first must be of type markup.
Obviously my understanding is not entirely correct.

Nevertheless the insertion done by convert-ly is not nice, imho. As a
mere user I'd think some bug happened.

Would it be feasable to do a type-checking for `headers' in
`headers-property-alist-chain'?
At least one could eliminate the (if ...) in the convert-rule.

Something at the lines of:

(define-public (headers-property-alist-chain headers)
  "Take a list of @code{\\header} blocks (Guile modules).  Return an
alist chain containing all of their bindings where the names have been
prefixed with @code{header:}.  This alist chain is suitable for
interpreting a markup in the context of these headers."
  (map
   (lambda (module)
     (map
      (lambda (entry)
        (cons
         (string->symbol
          (string-append "header:"
                         (symbol->string (car entry))))
         (cdr entry)))
      (ly:module->alist module)))
   (or headers '())))
^^^^^^^^^^^^^^^^^
Or if this to bold/optimistic:
(if (list? headers) headers '())

Cheers,
  Harm