Adding punctuation to the end of an extender in melismata

Punctuation can be added to the end of an extender in melismata by overriding the default stencil for LyricExtender.

For convenience, this snippet applies the stencil override as a tweak to the extender event.

\version "2.24.0"

%% http://lsr.di.unimi.it/LSR/Item?id=643

%LSR contributed by Neil Puttock

#(define (extend text . padding)
   (let ((extender (make-music 'ExtenderEvent))
	 ;; optional padding
	 (padding (if (pair? padding)
		      (car padding)
		      0)))
     #{ 
       \tweak 
         stencil
         #(lambda (grob)
           (let* ((orig (ly:grob-original grob))
                  (siblings (ly:spanner-broken-into orig)))
           
             (if (or (null? siblings)
                 (and (>= (length siblings) 2)
                      (eq? (car (last-pair siblings)) grob)))
             (ly:stencil-combine-at-edge
               (ly:lyric-extender::print grob)
               X RIGHT
               (grob-interpret-markup grob text)
               padding))))
         $extender
     #}))

%Define custom extenders, first with extra padding
extendComma = #(extend "," 0.2)
extendExclaim = #(extend "!")

\score {  
  <<
    \new Staff \new Voice = melody \relative c' {
      c4( d e f)
      g4( f e2)
    }
    \new Lyrics \lyricsto melody {
      Aah \extendComma
      Ooh \extendExclaim
    }
  >>
  \layout {
    \context {
      \Lyrics
      \consists "Tweak_engraver"
    }
  }
}