From 75a8fa3a466fbb86ea2be5ea2afa429f50b27bce Mon Sep 17 00:00:00 2001
From: Simon Ruderich <simon@ruderich.org>
Date: Sun, 31 Aug 2025 10:28:41 +0200
Subject: [PATCH] Workaround broken ICS files with empty RDATE

---
 CHANGES.rst                                   |  1 +
 docs/credits.rst                              |  1 +
 src/icalendar/cal/component.py                |  3 +++
 src/icalendar/tests/calendars/empty_RDATE.ics | 19 +++++++++++++++++++
 4 files changed, 24 insertions(+)
 create mode 100644 src/icalendar/tests/calendars/empty_RDATE.ics

diff --git a/CHANGES.rst b/CHANGES.rst
index 3d1540e..9683c33 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -26,6 +26,7 @@ Minor changes:
 - Add ``new()`` method to ``vCalAddress`` class for consistent API usage. The method supports all RFC 5545 parameters including ``CN``, ``CUTYPE``, ``DELEGATED-FROM``, ``DELEGATED-TO``, ``DIR``, ``LANGUAGE``, ``PARTSTAT``, ``ROLE``, ``RSVP``, and ``SENT-BY``, with automatic ``mailto:`` prefix handling. See `Issue 870 <https://github.com/collective/icalendar/issues/870>`_.
 - Refactor ``set_duration`` methods in ``Event`` and ``Todo`` classes to eliminate code duplication by extracting common logic into shared ``set_duration_with_locking()`` function in ``icalendar.attr``. See `Issue 886 <https://github.com/collective/icalendar/issues/886>`_.
 - Make coverage submission optional for CI
+- Accept and ignore non-standard empty ``RDATE`` fields when parsing ICS files.
 
 Breaking changes:
 
diff --git a/docs/credits.rst b/docs/credits.rst
index ea5dd85..566e61d 100644
--- a/docs/credits.rst
+++ b/docs/credits.rst
@@ -39,6 +39,7 @@ icalendar contributors
 - Russ <russ@rw.id.au>
 - `Sashank Bhamidi <https://github.com/SashankBhamidi>`_
 - Sidnei da Silva <sidnei@enfoldsystems.com>
+- Simon Ruderich <simon@ruderich.org>
 - Stanislav Láznička <slaznick@redhat.com>
 - Stanislav Ochotnicky <sochotnicky@redhat.com>
 - Stefan Schwarzer <sschwarzer@sschwarzer.net>
diff --git a/src/icalendar/cal/component.py b/src/icalendar/cal/component.py
index 081f013..e7429d1 100644
--- a/src/icalendar/cal/component.py
+++ b/src/icalendar/cal/component.py
@@ -379,6 +379,9 @@ class Component(CaselessDict):
                         parsed_components = [
                             factory(factory.from_ical(vals, params["TZID"]))
                         ]
+                    # Workaround broken ICS files with empty RDATE
+                    elif name == "RDATE" and vals == "":
+                        parsed_components = []
                     else:
                         parsed_components = [factory(factory.from_ical(vals))]
                 except ValueError as e:
diff --git a/src/icalendar/tests/calendars/empty_RDATE.ics b/src/icalendar/tests/calendars/empty_RDATE.ics
new file mode 100644
index 0000000..ffc2c95
--- /dev/null
+++ b/src/icalendar/tests/calendars/empty_RDATE.ics
@@ -0,0 +1,19 @@
+BEGIN:VCALENDAR
+PRODID:-//Events Calendar//iCal4j 1.0//EN
+CALSCALE:GREGORIAN
+VERSION:2.0
+METHOD:PUBLISH
+BEGIN:DAYLIGHT
+TZNAME:CEST
+TZOFFSETFROM:+0100
+TZOFFSETTO:+0200
+DTSTART:19160430T230000
+RDATE:
+RDATE:
+RDATE:
+RDATE:
+RDATE:
+RDATE:
+RDATE:
+END:DAYLIGHT
+END:VCALENDAR