[luatex] tex.fontidentifier vs. \pdftracingfonts

[Robert]

On 03.04.16 18:10, I wrote:
> tex.fontidentifier is supposed to return the csname of a font, but if
> \pdftracingsfonts=1, it will additionally include the fontname, which is
> not what I would expect:
>
> \input luaotfload.sty
> \font\x = "Latin Modern Roman" \x
> \pdftracingfonts1
> \directlua{texio.write_nl(tex.fontidentifier(font.current()))}
> \bye
>
> yields `\x ("Latin Modern Roman")' instead of `\x'.
>
> (This is with luatex 0.80.)

...and still with 0.95, where \pdftracingfonts has been renamed to 
\tracingfonts (which, BTW, conflicts with the tracefnt package).

Furthermore, somewhat related, with \tracingoutput=1, the log file does 
not contain any info about font expansion:

\ifx\directlua\undefined
  \font\x = cmr10 at 12pt\x
  \pdftracingfonts1
  \pdfadjustspacing2
  \pdffontexpand\x 20 20 1 autoexpand
\else
  \input luaotfload.sty
  \font\x = "Latin Modern Roman" at 12pt \x
  \tracingfonts1
  \adjustspacing2
  \expandglyphsinfont\x 20 20 1 autoexpand
\fi
  \tracingoutput1
  \showboxdepth\maxdimen
  \showboxbreadth\maxdimen
  \hsize=1pt
Test
  \bye

With pdftex, this will yield lines like:

| ...\x (cmr10-20 at 12.0pt) T

(font, expansion value, size),
whereas with luatex, it's just:

|...\x ("Latin Modern Roman") T

(no expansion value, no step).

Best,
-- 
  Robert