Re: [RFC] Quoting property names in tag/property matches [Was: [BUG?] Matching tags: & operator no more implicit between tags and special property]

[Jens Schmidt <jschmidt4gnu@vodafonemail.de>]

> On 2023-08-23  12:31, Ihor Radchenko wrote:
> 
>> Jens, we got an edge case with "-", after all.
>>
>> What is happening here is that the new parser
>> (https://orgmode.org/list/9132e58f-d89e-f7df-bbe4-43d53a2367d2@vodafonemail.de)
>> treats the above match string as
>>
>> property "tag-TODO" not equal "TODO"
>>
>> instead of
>>
>> not tag equal "tag" and not TODO equal "TODO"

Right.  And you already provided in the other branch of this
discussion a direction how to resolve that:

> [...] In case of ambiguity TAG1-TAG2-TAG3-PROP="" like we see here, we
> should prefer multiple shorter conditions: TAG1 && -TAG2 && -TAG3 && PROP=""
> 
> When "TAG1-TAG2" is an actual tag name with dash, we may allow escaping.

But I'd like to clarify that.  From the Org syntax

  https://orgmode.org/worg/org-syntax.html#Headings

I understood that tag names cannot contain minus characters,
and `org-tag-re' does not match any, either.  So we are talking
about property names only, right?  At least I'll do so in the
following ...


Then the question is what quoting scheme to use for property
names.  The previous one used before my commit f689eb4

  (A) "\\-" => "-"

never has been documented and never has been working properly,
since the *matching* of these was done on *prop* names, but
the *unescaping* on *tag* names.  So we are basically free to
come up with something new.

Some obvious choice would be a simpler single backslash

  (B) "\-" => "-"

And when I have been "fixing" the parser, I also thought that

  (C) ":...:" => "..."

would give a nice and somewhat logical quoting scheme.  That is,
if a property name contains "special" characters, it could be
surrounded by colons to quote these.

So we have so far quoting schemes A, B, C, with my preference
being C.  Any other proposals?


I'll focus on C, where there is one big cave-at:  The main
regexp in `org-make-tags-matcher' also allows for (undocumented)
colons as inclusive search term separator:

  ;; exclusion and inclusion (the latter being implicit)
  "\\(?1:[-+:]\\)?"
            ^
   
Which collides with the colons used by quoting scheme C.  I'd
rather sacrifice that use of colon as search term separator,
TBH.

Given the property name syntax in

  https://orgmode.org/worg/org-syntax.html#Node_Properties

the subre in `org-make-tags-matcher' to match property names
should then look similar to

  "\\(?5:[[:alnum:]_]+\\|:[^[:space:]]+?:\\)"

, right (colons being stripped off later)?  I'm really asking
about the trailing plus signs here, but these do not seem to
make sense in property queries.


What do you think?