Brace delimited parameter in action

[muzimuzhi]

\documentclass{article}
\usepackage{unravel}

\def\mycmd#1#{}
\unravel{\mycmd arg{}}

\begin{document}
\end{document}

• Expected:

  [===== Step 1 =====] \mycmd = macro:#1#{->{}

• Actual:

  [===== Step 1 =====] \mycmd = macro:#1{->{

Note the trailing # in parameter text and ending } for replacement text are both missing.

||
|> \mycmd arg{}

[===== Step 1 =====] \mycmd = macro:#1{->{
||
|> {}

[===== Step 2 =====]
<| {
||
|> }

[===== Step 3 =====]
<| {}
||
|>

[===== End =====]

[blefloch]

Thanks for the many relevant issues you raised and sorry that they lingered for so long.

For this one, I don't see why you would expect macro:#1#{->{}. In fact, I simply use the output of \meaning\mycmd here, which is macro:#1{->{, which seems fine: it means that #1 is delimited by a left brace and the brace is left in the input stream. So I'm tempted to close it as not an issue, do you agree?

On the other hand, these types of macros are problematic for another reason as they break an optimization, see #61, thanks for pointing me to this case.

[muzimuzhi]

In fact, I simply use the output of \meaning\mycmd here, which is macro:#1{->{, which seems fine: it means that #1 is delimited by a left brace and the brace is left in the input stream.

You're right. I totally forgot the form of output of \meaning\mycmd here.