[BUG] Org 9.5.3 fails to display agenda (error "rx form ‘regexp’ requires args satisfying ‘stringp’")

[Edmund Christian Herenz <eherenz@eso.org>]

Dear Developers,

thank you for the hard work on Org-mode.  I recently updated to 9.5.3
using elpa on GNU Emacs 26.1 and suddenly org-mode fails to display
the agenda (Debug message below).  This is not a smooth upgrade
experience, and some tests on core-functionality on supported emacs
versions would be appreciated.

Debugger entered--Lisp error: (error "rx form ‘regexp’ requires args satisfying ‘stringp’")
  signal(error ("rx form ‘regexp’ requires args satisfying ‘stringp’"))
  error("rx form `%s' requires args satisfying `%s'" regexp stringp)
  rx-check((regexp org-ts-regexp3))
  rx-regexp((regexp org-ts-regexp3))
  rx-form((regexp org-ts-regexp3) |)
  #f(compiled-function (x) #<bytecode 0x12af431>)((regexp org-ts-regexp3))
  mapconcat(#f(compiled-function (x) #<bytecode 0x12af431>) ((regexp org-ts-regexp3) (regexp org-element--timestamp-regexp)) "\\|")
  rx-or((or (regexp org-ts-regexp3) (regexp org-element--timestamp-regexp)))
  rx-form((or (regexp org-ts-regexp3) (regexp org-element--timestamp-regexp)))
  rx-to-string((or (regexp org-ts-regexp3) (regexp org-element--timestamp-regexp)) t)
  #f(compiled-function (&rest regexps) #<bytecode 0x1291fd9>)((or (regexp org-ts-regexp3) (regexp org-element--timestamp-regexp)))
  (rx (or (regexp org-ts-regexp3) (regexp org-element--timestamp-regexp)))
  (if (eq extended 'agenda) (rx (or (regexp org-ts-regexp3) (regexp org-element--timestamp-regexp))) org-ts-regexp3)
  (if extended (if (eq extended 'agenda) (rx (or (regexp org-ts-regexp3) (regexp org-element--timestamp-regexp))) org-ts-regexp3) org-ts-regexp2)
  (let* ((regexp (if extended (if (eq extended 'agenda) (rx (or (regexp org-ts-regexp3) (regexp org-element--timestamp-regexp))) org-ts-regexp3) org-ts-regexp2)) (pos (point)) (match\? (let ((boundaries (org-in-regexp regexp))) (save-match-data (cond ((null boundaries) nil) ((eq extended 'lax) t) (t (or (and (eq extended 'agenda) (or (org-at-planning-p) (org-at-property-p) (and (bound-and-true-p org-agenda-include-inactive-timestamps) (org-at-clock-log-p)))) (eq 'timestamp (save-excursion (when (= pos (cdr boundaries)) (forward-char -1)) (org-element-type (org-element-context))))))))))) (cond ((not match\?) nil) ((= pos (match-beginning 0)) 'bracket) ((= pos (1- (match-end 0))) 'bracket) ((= pos (match-end 0)) 'after) ((org-pos-in-match-range pos 2) 'year) ((org-pos-in-match-range pos 3) 'month) ((org-pos-in-match-range pos 7) 'hour) ((org-pos-in-match-range pos 8) 'minute) ((or (org-pos-in-match-range pos 4) (org-pos-in-match-range pos 5)) 'day) ((and (or (match-end 8) (match-end 5)) (> pos (or (match-end 8) (match-end 5))) (< pos (match-end 0))) (- pos (or (match-end 8) (match-end 5)))) (t 'day)))
  org-at-timestamp-p(agenda)
  org-agenda-get-timestamps(nil)
  org-agenda-get-day-entries("/home/ehere/science_works/calendar.org" (4 25 2022) :deadline :scheduled :timestamp :sexp)
  apply(org-agenda-get-day-entries "/home/ehere/science_works/calendar.org" (4 25 2022) (:deadline :scheduled :timestamp :sexp))
  org-agenda-list(nil)
  funcall-interactively(org-agenda-list nil)
  call-interactively(org-agenda-list)
  org-agenda(nil)
  funcall-interactively(org-agenda nil)
  call-interactively(org-agenda nil nil)
  command-execute(org-agenda)

Best regards,
Christian

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Edmund Christian Herenz (ESO Fellow)     Office: M152
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