[luatex] glue fill order

[David Carlisle]

If I use tex.setglue the glue stretch and shrink orders come out one
less than I expect, I expected 1=fil, 2=fill, but I get 1=fi(?) 2=fil,
3=fill




\directlua{
local sp=65536
tex.setglue(100, 5*sp,1*sp,0,0,0)
tex.setglue(101, 5*sp,1*sp,0,1,0)
tex.setglue(102, 5*sp,2*sp,0,2,0)
tex.setglue(103, 5*sp,3*sp,0,3,0)
tex.setglue(104, 5*sp,4*sp,0,4,0)
}

\immediate\write20{100: \the\skip100}
\immediate\write20{101: \the\skip101}
\immediate\write20{102: \the\skip102}
\immediate\write20{103: \the\skip103}
\immediate\write20{104: \the\skip104}

\skip105= 5pt plus 1fil
\immediate\write20{105: \the\skip105}

\tracingonline1
\scrollmode
\setbox0\hbox to 10pt{\hskip\skip101 \showlists}
\showbox0
\bye


produces a terminal output



This is LuaTeX, Version 1.10.0 (TeX Live 2019)
 restricted system commands enabled.
(./fill.tex
100: 5.0pt plus 1.0pt
101: 5.0pt plus 1.0fi
102: 5.0pt plus 2.0fil
103: 5.0pt plus 3.0fill
104: 5.0pt plus 4.0filll
105: 5.0pt plus 1.0fil


### restricted horizontal mode entered at line 22
\glue 5.0 plus 1.0fi
spacefactor 1000
### vertical mode entered at line 0
prevdepth ignored

! OK.
l.22 \setbox0\hbox to 10pt{\hskip\skip101 \showlists
                                                  }
> \box0=
\hbox(0.0+0.0)x10.0, glue set 5.0fi, direction TLT
.\glue 5.0 plus 1.0fi

! OK.
l.23 \showbox0

)
(see the transcript file for additional information)
warning  (pdf backend): no pages of output.




David