Second argument for .code 2 args is not optional

[fritzw]

In section "87.4.3 Defining Key Codes" under .code 2 args, the manual states:

The second argument is optional: if it is not provided, it will be the empty string. Because of the special way the 'value' is parsed, if you set 'value' to, for instance, first (without any braces), then #1 will be set to f and #2 will be set to irst.

This appears to be false. If you pass a single braced argument, pgfkeys will always parse the first character as #1 and the rest as #2, even if you use double braces. Only when using triple braces, does it work as advertised in the manual.

Minimal working example (MWE)

\documentclass{article}
\usepackage{tikz}

\tikzset{
	my plain key/.code 2 args={1=#1, 2=#2},
}

\begin{document}
\pgfkeys{/tikz/my plain key={Expected result}{}}

\pgfkeys{/tikz/my plain key={First only}}

\pgfkeys{/tikz/my plain key={First}{Second}}

\pgfkeys{/tikz/my plain key={{Double Braces}}}

\pgfkeys{/tikz/my plain key={{{Triple Braces}}}}
\end{document}

Result:

[hmenke]

Exact duplicate of #991. Please search existing issues before opening a new one.

[fritzw]

Sorry, I did a search for "code 2 args" but that did not turn up anything. Obviously I forgot to search for closed issues as well. :-(