Re: [Patch v4] lib: regexp matching in 'subject' and 'from'

[Tomi Ollila <tomi.ollila@iki.fi>]

On Thu, Feb 09 2017, David Bremner <david@tethera.net> wrote:

> Jani Nikula <jani@nikula.org> writes:
>
>>
>> Theoretically "/" is an acceptable character in message-ids [1]. Rare,
>> unlikely, but acceptable. Searching for message-id's beginning with "/"
>> would have to use regexps, which would break in all sorts of ways
>> throughout the stack. I don't think there are handy alternatives to
>> "/<regex>/", given the characters that are acceptable in message-ids,
>> but this is something to think about.
>
> Would telling the user to \ escape ( or double /) the initial / be good

a while ago I thought this double // but dismissed it quickly 
(re-searching just for single quote can be useful...) In the rare
cases anyone needs to disable regex processing, imo this \ is the
best idea i've (not) come up with.

some command line testing with(and -out) quoting:

$ printf %s\\n  id:\/some/crazy/message-id
id:/some/crazy/message-id

$ printf %s\\n  "id:\/some/crazy/message-id"
id:\/some/crazy/message-id

$ printf %s\\n  'id:\/some/crazy/message-id'
id:\/some/crazy/message-id


$ printf %s\\n  id:\\/some/crazy/message-id
id:\/some/crazy/message-id

$ printf %s\\n  "id:\\/some/crazy/message-id"
id:\/some/crazy/message-id

$ printf %s\\n  'id:\\/some/crazy/message-id'
id:\\/some/crazy/message-id

so:
$ printf %s\\n  'id:"\/some/crazy/message-id with spaces"'
id:"\/some/crazy/message-id with spaces"


> enough there? This would disable regex processing.  I guess this goes
> back to someone's earlier suggestion.  A third option would be to use
> single quotes there ("id:'/foo'"), but that isn't really consistent with
> either Xapian 
> or usual regex conventions.

$ printf %s\\n 'id:"'\''/foo with spaces ;D'\''"'
id:"'/foo with spaces ;D'"

or, perhaps this is clearer >;)

$ printf %s\\n 'id:"'"'"'/foo with spaces ;D'"'"'"'
id:"'/foo with spaces ;D'"

>
> So I guess my favourite idea ATM is to use id:\/some/crazy/message-id
> FWIW, I don't have any such message ids.
>
>> For example, could the regexp matcher for message-ids first check if the
>> "regexp" is a strict match with "/" and all, and accept those? This
>> might be a reasonable workaround if it can be made to work.
>
> We're building a query, so I think the equivalent is to make an OR, with
> the exact match and the regex posting source. That could be done,
> although I'm a bit uneasy about how this makes the syntax for id:
> different, so id:/foo would be legit, but from:/foo would be an error.
> Maybe the dwim-factor is worth it.
>
> d