What is the deal with `org-agenda-skip-deadline-prewarning-if-scheduled', 'pre-scheduled, and specific deadline lead times?

What is the deal with `org-agenda-skip-deadline-prewarning-if-scheduled', 'pre-scheduled, and specific deadline lead times?

[Trevor Murphy]

Hi, list!  tl;dr given the setting alluded to in the subject line, 
I'm
dissatisfied with the behavior of the following example 
(scheduling and
deadline timestrings use "today" as pseudocode):

* TODO check deadline skipping with specific lead time and 
  'pre-scheduled
DEADLINE: <today+2d -3d> SCHEDULED: <today+1d>

I would like to hack the code to change the behavior, but I'm 
concerned about
breaking a zillion other things at the same time.  Comments and 
suggestions
welcome.

Still with me?  Longer description below:

The documentation says
(http://orgmode.org/manual/Deadlines-and-scheduling.html):

You can specify a different lead time for warnings for specific 
deadlines
using the following syntax.  Here is an example with a warning 
period of 5
days =DEADLINE: <2004-02-29 Sun -5d>=.  This warning is 
deactivated if the
task gets scheduled and you set
=org-agenda-skip-deadline-prewarning-if-scheduled= to =t=.

I have o-a-s-d-p-i-s set to 'pre-scheduled.  Suppose today is 
Wednesday,
2014-10-08, and I create an agenda file "example.org" with the 
following
contents:

* TODO check deadline skipping with specific lead time
DEADLINE: <2014-10-10 Fri> SCHEDULED: <2014-10-09 Thu>

Then the deadline warning does not appear in today's agenda.  This 
is what I
want, and I think this is what I should expect with the 
'pre-scheduled
setting.

However, if I use the following contents instead (note the 
specified warning
period):

* TODO check deadline skipping with specific lead time
DEADLINE: <2014-10-10 Fri -3d> SCHEDULED: <2014-10-09 Thu>

The deadline warning *reappears* in today's agenda.  I think this 
is a bug.  I
think I've ruled out the personal-configuration sources of the 
behavior, and
instead traced it to the following code in 
`org-agenda-get-deadlines':

  (setq wdays (if suppress-prewarning
                  (let ((org-deadline-warning-days 
                  suppress-prewarning))
                    (org-get-wdays s))
                (org-get-wdays s))
                ...)

In `org-agenda-get-deadlines', with o-a-s-d-p-i-s set to 
'pre-scheduled, the
code stores the gap between scheduling and deadline information in 
the local
variable `suppress-prewarning'.  As you can see in the citation 
above, o-a-g-d
then let-binds the user option `org-deadline-warning-days' to 
match and calls
`org-get-wdays' to figure out the appropriate amount of 
warning-day lead time.

But!  Check out what `org-get-wdays' does with specific warning 
periods in the deadline timestring:

  (cond
    ...
   ((string-match "-\\([0-9]+\\)\\([hdwmy]\\)\\(\\'\\|>\\| \\)" 
   ts)
    ;; lead time is specified.
    (floor (* (string-to-number (match-string 1 ts))
              (cdr (assoc (match-string 2 ts)
                          '(("d" . 1)    ("w" . 7)
                            ("m" . 30.4) ("y" . 365.25)
                            ("h" . 0.041667)))))))

`org-get-wdays' never checks `org-deadline-warning-days' in this 
branch, and
so never gets a chance to see the `suppress-prewarning' 
information passed in
from `org-agenda-get-deadlines'.

At this point I'm stuck.  I'd like to hack into `org-get-wdays' 
some code that
says "Yes, there's a specific warning period.  However, there's 
also some
prewarning suppression going on, so we should take that into 
consideration."
But I'd like to avoid changing the existing behavior for when 
there is no
prewarning suppression and the specific warning period just 
happens to be
longer than the user option `org-deadline-warning-days'.

If you're still reading, thanks.  Please let me know if you have 
any
suggestions, questions, or comments about what I'm trying to do.

--
Trevor Murphy
GnuPG Key: 0x83881C0A