Replacing \newcommand by \DeclareRobustCommand makes a new command robust. But what about \renewcommand? Is there a command to robustly renew a command?
It would be possible to first use \renewcommand and then use \MakeRobustCommand of the makerobust package, but isn't there a "one-command-way"? (And does that one provide a starred form, same as \DeclareRobustCommand*?)
The etoolbox command provides a \renewrobustcmd macro as well as a \newrobustcmd (and their starred versions). Both use the new e-TeX way to define robust commands. Note that \DeclareRobustCommand is not checking if the command already exists and will not cause any errors if it does. This might result in trouble when a macro is defined twice on two different places and you don't know about it. The etoolbox macro include the checks.
"\DeclareRobustCommand is not checking if the command already exists and will not cause any errors if it does." - That is exactly the reason because of which I asked for a robust \renewcommand version. As I did not state that, it is good that you wrote it in the answer. Thanks!
etoolbox you could also redefine the macro with a dummy \renewcommand to check if it exists and then use \DeclareRobustCommand to redefine it in a robust way.
– Martin Scharrer
Jan 30 '18 at 14:22
\NewDocumentCommandfromxparse. – Flow Aug 25 '18 at 17:09