mc.ext.ini conversion - incorrect escaping in the Regex section

[fedy]

It looks like in mc version 4.8.31 the mc.ext.ini file's Regex= expressions needs double escaping of the special characters (like .)

For example for mp4 videos the (auto generated) default is:

[mp4]
Regex=\\.(mp4|m4v|mpe?g)$

Probably as a result of an automatic conversion of this file from previous format I ended up with a config where the . in Regexes are prepended with just a single \. That result in most setting using Regex just not working. Newly generated mc.ext.ini contains double escaped Regexes like above and works just fine, but all previous user customization are lost.

Not sure if the need for double escaping was intended, but there seems to be a mismatch between the currently required format and the format produced by the conversion.

[fedy]

Correction - example again (codeblock):

[mp4]
Regex=\\.(mp4|m4v|mpe?g)$
RegexIgnoreCase=true
Include=video

[andrew_b]

Replying to fedy:

It looks like in mc version 4.8.31 the mc.ext.ini file's Regex= expressions needs double escaping of the special characters (like .)

Correct. This is already done in #4502.

Probably as a result of an automatic conversion of this file from previous format

mc doesn't provide any automatic conversion for this file.

[fedy]

Sorry, wrong assumption.

Investigated further:
The Regex syntax change (regarding escaping) must have happened between versions 4.8.30 and 4.8.31 (specifically the ones distributed in Fedora 38 and Fedora 40).

It has probably something to do with the (change in?) glib handling mentioned in the top of the newly generated file in the Regex= syntax section , quoting:

#            An unescaped backslash \ is handled as invalid escape sequences in glib = 2.77.3 and
#            glib >= 2.79 (https://gitlab.gnome.org/GNOME/glib/-/issues/3094), therefore backslash
#            must be escaped.

... still, incompatible change so maybe this report (or possibly some FAQ entry?) might help others looking for reasons while suddenly half of their file associations are not working.