Re: [PATCH] Clarify that REST is not supported on the start TIME in a time-range timestamp.

[Ihor Radchenko]

"Tom Alexander" <tom@fizz.buzz> writes:

> Potentially related, org-mode is accepting this malformed timestamp from[1]:
> ```
> <2016-02-14 Sun ++y>
> ```
>
> The org-mode documentation[2] only includes REST with TIME, defining TIME as 
> "H:MMREST". The above does not have any TIME but it accepts the timestamp 
> anyway:
> ...
> Perhaps that grammar is wrong and REST needs to be separated from TIME?

We have no internal consistency here, AFAIR.
The actual matching is done with

(defconst org-element--timestamp-regexp
  (concat org-ts-regexp-both
          "\\|"
          "\\(?:<[0-9]+-[0-9]+-[0-9]+[^>\n]+?\\+[0-9]+[dwmy]>\\)"
          "\\|"
          "\\(?:<%%\\(?:([^>\n]+)\\)>\\)")
  "Regexp matching any timestamp type object.")

with org-ts-regexp-both matching

(rx (seq
       (= 4 digit) "-" (= 2 digit) "-" (= 2 digit)
       (optional " " (*? nonl))))

(and also brackets)

Then, `org-element-timestamp-parser' looks for DATE/TIME/REPEATERS/etc
inside the above match, disregarding any order:

(string-match
                    
"[012]?[0-9]:[0-5][0-9]\\(-\\([012]?[0-9]\\):\\([0-5][0-9]\\)\\)"
                    date-start)

(string-match "\\([.+]?\\+\\)\\([0-9]+\\)\\([hdwmy]\\)"
                                 raw-value)                    

(string-match "\\(-\\)?-\\([0-9]+\\)\\([hdwmy]\\)" raw-value)

However, not all the Org code is using org-element parser yet. Certain
parts of Org are matching manually using a separate, more strict
regexps, like org-ts-regexp0, org-ts-regexp1, ...

So, we chose to use a more strict definition in org-syntax for the time
being, before we consolidate things together in more uniform ways.

As for the problem with REST you raised, I am inclined to remove it from
syntax doc for the time being - it only creates more confusion,
unfortunately.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
or support my work at <https://liberapay.com/yantar92>