Extend naming conventions with things to avoid

[elbrujohalcon]

Currently, our naming convention rules only allow for a single regex that identifies what is permitted/valid.
It would be nice to add an additional forbidden regex to identify things that are not valid, like function names starting with do_.

Ref: WhatsApp/erlfmt#91

[paulo-ferraz-oliveira]

For semantics purposes, a forbidden keyword might make sense... but then you'd always have to have an order in evaluation: if you accept and negate a given string, which one is valid?

Have you considered negative lookaheads, like ^(?!(^do_)).*$?

> {ok,RE} = re:compile("^(?!do_).*$").
{ok,{re_pattern,0,0,0,
                <<69,82,67,80,87,0,0,0,16,0,0,0,1,128,0,0,255,255,255,
                  255,255,255,...>>}}
> re:run("ado_", RE).                        
{match,[{0,4}]}
> re:run("do_", RE). 
nomatch

[elbrujohalcon]

HA! I didn't know about negative lookaheads.
I still think that a forbidden regex would be clearer and the usual semantics is "allow everything that matches with regex except if it matches forbidden regex". I would go with that, with the default for forbidden being none.

[paulo-ferraz-oliveira]

with the default for forbidden being none.

It could even be undefined :-)