Edition Engraver bug?

[Stefano Troncaro]

Hi everyone! I tried to isolate the issue with Tie directions that I posted earlier and I'm fairly confident I've stumbled upon a bug.

Look at the output of this snippet (Sorry for the length, I made it as short as I could)

\version "2.19.80"
\language "english"
\include "oll-core/package.ily"
\loadPackage edition-engraver
\addEdition test
\consistToContexts #edition-engraver Voice

\layout {
  \context {
    \Score
    \time 6/4
    \omit TimeSignature
    \omit Clef
  }
}

forceRebelTie =
#(define-music-function (dir) (ly:dir?)
   #{
     \override Tie.before-line-breaking =
     #(lambda (grob)
        (ly:grob-set-property! grob 'direction dir)) #} )

ovA = \once \tieDown
ovB = \once \override Tie.direction = #DOWN
ovC = \once \forceRebelTie #DOWN

formA = \new Staff \with { instrumentName = "All V1" } << 
  \new Voice \relative c'' { \voiceOne b~ 4 4~ 4 4~ 4} >>
formB = \new Staff \with { instrumentName = "1V V1" } <<
  \new Voice \relative c'' { b~ \voiceOne 4 \oneVoice 4~ \voiceOne 4 \oneVoice 4~ \voiceOne 4 } >>
controlA = \new Staff \with { instrumentName = "No EE" } <<
  \new Voice \relative c'' { \voiceOne \ovA b~ 4 4~ 4 4~ 4 } >>
controlB = \new Staff \with { instrumentName = "No EE" } <<
  \new Voice \relative c'' { \voiceOne \ovB b~ 4 4~ 4 4~ 4 } >>
controlC = \new Staff \with { instrumentName = "No EE" } <<
  \new Voice \relative c'' { \voiceOne \ovC b~ 4 4~ 4 4~ 4 } >>


\markup "Results with \\tieDown"

\editionMod test 1 0 Voice.A \ovA
\editionMod test 1 0 Voice.B \ovA
\score {
  \new StaffGroup <<
    \formA
    \formB
    \controlA
  >>
}

\markup "Results with \\override Tie.direction"

\editionMod test 1 0 Voice.D \ovB
\editionMod test 1 0 Voice.E \ovB
\score {
  \new StaffGroup <<
    \formA
    \formB
    \controlB
  >>
}

\markup "Results with ly:grob-set-property!"

\editionMod test 1 0 Voice.G \ovC
\editionMod test 1 0 Voice.H \ovC
\score {
  \new StaffGroup <<
    \formA
    \formB
    \controlC
  >>
}

\markup "No overrides (default behavior for comparison)"
\score {
  \new StaffGroup <<
    \formA
    \formB
  >>
}

When \voiceOne is in full effect, both \once \tieDown and \once \override Tie.direction seem to have a permanent effect that kicks in after the moment they are used, which is exactly the opposite to what they should do (take effect only in the moment they are called and revert to the previous behavior after). This is very clear when you compare the All V1 Staff with the No EE Staff: the All V1 behaves in the exact opposite way.

I have absolutely no idea about why this may be happening, but I'm certain that one should expect the EE to achieve the same results that manually writing the code in the desired place and moment would.

Hopefully Jan-Peter or someone more knowledgeable than I can look into it!

I hope this "research" can be useful!

Stéfano