If I have a magic Vim regex in a string literal, is there a way to convert the whole regex into an alternative representation that uses a different magic mode, so I could paste that equivalent regex into source code?
For instance, if I want to convert this magic-mode pattern:
'\m-\=\<\d\+L\=\>\|0[xX][0-9a-fA-F]\+\>'
to very-magic-mode to make it more readable, something like:
'\v-=<\d+L=>|0[xX][0-9a-fA-F]+>'
I often make mistakes trying to convert them by hand.
The command
:s\v\\(\W)/\1/
should suffice to transform most any pattern into \v mode. It won't swap out the lil' \m marker though - and to my knowledge that's impossible in a single replacement. It's short enough to type manually though, and then you can just do :s/\\m/\\v for the mode marker.
\W is shorthand for [^a-zA-Z0-9_] which is the (negated) set of characters that very magic mode operates on. This just deletes any backslashes immediately preceding one of those characters.
Known issue: This will replace \\ inside strings to \. You could replace \W with \c[^a-z0-9\_] to mitigate this, but it'll still mess up your regex literal if you run it multiple times and also fail on longer escape strings (containing \\\\ for example)
Update: The original question makes it unclear if you need to transform \v back to \m, but the command there is:
:s/\v(\\)@<!(\c[^a-z0-9\-\\\[\]\'_])/\\\2/
based on @Wolfie's answer:
:subs #\v\\(\W)#\1#gc
to use # instead of / (I hate / and \ together):
:subs ^\/^#^gc
May need some manual check
[0-9]+into a no magic one... ;-)