fix: CalDAV Autodiscovery - XML war doppelt verschachtelt

Property-Elemente wurden unter einem Container mit demselben Tag
erzeugt, z.B.:
  <current-user-principal>
    <current-user-principal>    <!-- falsch, doppelt -->
      <href>/dav/adam/</href>
    </current-user-principal>
  </current-user-principal>

Clients wie DAVx5 und Thunderbird erkennen dadurch den Principal
nicht und melden "Kein CalDAV-Dienst gefunden". XML-Generierung
umgebaut - Response-Helfer bekommen jetzt eine populate_prop-
Callback, die die tatsaechlichen Property-Children direkt ins
<prop>-Element setzt.

Zusaetzlich:
* /.well-known/caldav und /carddav akzeptieren jetzt auch PROPFIND,
  OPTIONS, HEAD (einige Clients halten die Methode beim ersten
  Aufruf bei).
* Kalender-Response enthaelt current-user-privilege-set (leer, als
  Signal dass der Client nicht ACL-abhaengig pruefen muss).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/__init__.py

@@ -92,15 +92,14 @@ def create_app(config_class=Config):
     app.register_blueprint(dav_bp)
 
     # Well-known URLs for CalDAV/CardDAV auto-discovery (iOS, DAVx5, etc.).
-    # RFC 6764 says we should do a 301 to the DAV root; clients then PROPFIND
+    # RFC 6764 requires 301; PROPFIND auf /.well-known/caldav gibt manche
-    # to walk principal/home-set/calendars. The path intentionally does NOT
+    # Clients direkt ab (Method-Preservation) - also auch dort akzeptieren
-    # include a username - the user authenticates via HTTP Basic and the
+    # und auf /dav/ weiterleiten. Alle HTTP-Methoden werden registriert.
-    # server routes them to their own principal.
+    @app.route('/.well-known/caldav', methods=['GET', 'PROPFIND', 'OPTIONS', 'HEAD'])
-    @app.route('/.well-known/caldav')
     def wellknown_caldav():
         return redirect('/dav/', code=301)
 
-    @app.route('/.well-known/carddav')
+    @app.route('/.well-known/carddav', methods=['GET', 'PROPFIND', 'OPTIONS', 'HEAD'])
     def wellknown_carddav():
         return redirect('/dav/', code=301)
 

backend/app/dav/caldav.py

@@ -139,79 +139,62 @@ def options(subpath=''):
 # PROPFIND
 # ---------------------------------------------------------------------------
 
-def _propstat_ok(href: str, props: dict) -> ET.Element:
+def _make_response(href: str, populate_prop) -> ET.Element:
-    """Build a <response> element with one 200 propstat containing the
+    """Build a <response><href/><propstat><prop>...</prop><status>200</status>
-    given (qname -> element or string or None) properties."""
+    </propstat></response> element. `populate_prop` is a callable that gets
+    the <prop> element and appends the actual property sub-elements to it."""
     resp = ET.Element(_qn('d', 'response'))
     ET.SubElement(resp, _qn('d', 'href')).text = href
     propstat = ET.SubElement(resp, _qn('d', 'propstat'))
     prop = ET.SubElement(propstat, _qn('d', 'prop'))
-    for qname, value in props.items():
+    populate_prop(prop)
-        el = ET.SubElement(prop, qname)
-        if isinstance(value, ET.Element):
-            el.append(value)
-        elif isinstance(value, list):
-            for child in value:
-                el.append(child)
-        elif value is not None:
-            el.text = str(value)
     ET.SubElement(propstat, _qn('d', 'status')).text = 'HTTP/1.1 200 OK'
     return resp
 
 
-def _resource_type(*kinds: str) -> ET.Element:
-    el = ET.Element(_qn('d', 'resourcetype'))
-    for k in kinds:
-        if k == 'collection':
-            ET.SubElement(el, _qn('d', 'collection'))
-        elif k == 'calendar':
-            ET.SubElement(el, _qn('c', 'calendar'))
-        elif k == 'principal':
-            ET.SubElement(el, _qn('d', 'principal'))
-    return el
-
-
 def _root_response(href: str, user: User) -> ET.Element:
-    principal = ET.Element(_qn('d', 'current-user-principal'))
+    def populate(prop):
-    ET.SubElement(principal, _qn('d', 'href')).text = f'/dav/{user.username}/'
+        rt = ET.SubElement(prop, _qn('d', 'resourcetype'))
-    return _propstat_ok(href, {
+        ET.SubElement(rt, _qn('d', 'collection'))
-        _qn('d', 'resourcetype'): _resource_type('collection'),
+        ET.SubElement(prop, _qn('d', 'displayname')).text = 'Mini-Cloud DAV'
-        _qn('d', 'displayname'): 'Mini-Cloud DAV',
+        cup = ET.SubElement(prop, _qn('d', 'current-user-principal'))
-        _qn('d', 'current-user-principal'): principal,
+        ET.SubElement(cup, _qn('d', 'href')).text = f'/dav/{user.username}/'
-    })
+    return _make_response(href, populate)
 
 
 def _principal_response(user: User) -> ET.Element:
     href = f'/dav/{user.username}/'
-    home = ET.Element(_qn('c', 'calendar-home-set'))
+
+    def populate(prop):
+        rt = ET.SubElement(prop, _qn('d', 'resourcetype'))
+        ET.SubElement(rt, _qn('d', 'collection'))
+        ET.SubElement(rt, _qn('d', 'principal'))
+        ET.SubElement(prop, _qn('d', 'displayname')).text = user.username
+        cup = ET.SubElement(prop, _qn('d', 'current-user-principal'))
+        ET.SubElement(cup, _qn('d', 'href')).text = href
+        pu = ET.SubElement(prop, _qn('d', 'principal-URL'))
+        ET.SubElement(pu, _qn('d', 'href')).text = href
+        home = ET.SubElement(prop, _qn('c', 'calendar-home-set'))
         ET.SubElement(home, _qn('d', 'href')).text = href
-    principal_url = ET.Element(_qn('d', 'principal-URL'))
+    return _make_response(href, populate)
-    ET.SubElement(principal_url, _qn('d', 'href')).text = href
-    return _propstat_ok(href, {
-        _qn('d', 'resourcetype'): _resource_type('principal', 'collection'),
-        _qn('d', 'displayname'): user.username,
-        _qn('c', 'calendar-home-set'): home,
-        _qn('d', 'principal-URL'): principal_url,
-    })
 
 
 def _calendar_response(user: User, cal: Calendar) -> ET.Element:
     href = _href_calendar(user.username, cal.id)
-    supported = ET.Element(_qn('c', 'supported-calendar-component-set'))
+
+    def populate(prop):
+        rt = ET.SubElement(prop, _qn('d', 'resourcetype'))
+        ET.SubElement(rt, _qn('d', 'collection'))
+        ET.SubElement(rt, _qn('c', 'calendar'))
+        ET.SubElement(prop, _qn('d', 'displayname')).text = cal.name
+        ET.SubElement(prop, _qn('c', 'calendar-description')).text = cal.description or ''
+        supported = ET.SubElement(prop, _qn('c', 'supported-calendar-component-set'))
         comp = ET.SubElement(supported, _qn('c', 'comp'))
         comp.set('name', 'VEVENT')
-    color_el = ET.Element(_qn('ic', 'calendar-color'))
+        ET.SubElement(prop, _qn('ic', 'calendar-color')).text = cal.color or '#3788d8'
-    color_el.text = cal.color or '#3788d8'
+        ET.SubElement(prop, _qn('cs', 'getctag')).text = _calendar_ctag(cal)
-    getctag = ET.Element(_qn('cs', 'getctag'))
+        ET.SubElement(prop, _qn('d', 'current-user-privilege-set'))
-    getctag.text = _calendar_ctag(cal)
+    return _make_response(href, populate)
-    return _propstat_ok(href, {
-        _qn('d', 'resourcetype'): _resource_type('collection', 'calendar'),
-        _qn('d', 'displayname'): cal.name,
-        _qn('c', 'calendar-description'): cal.description or '',
-        _qn('c', 'supported-calendar-component-set'): supported,
-        _qn('ic', 'calendar-color'): color_el.text,
-        _qn('cs', 'getctag'): getctag.text,
-    })
 
 
 def _calendar_ctag(cal: Calendar) -> str:
@@ -223,14 +206,15 @@ def _calendar_ctag(cal: Calendar) -> str:
 
 def _event_response(user: User, cal: Calendar, event: CalendarEvent, include_data: bool = False) -> ET.Element:
     href = _href_event(user.username, cal.id, event.uid)
-    props = {
+
-        _qn('d', 'getetag'): _etag_for_event(event),
+    def populate(prop):
-        _qn('d', 'getcontenttype'): 'text/calendar; charset=utf-8; component=VEVENT',
+        ET.SubElement(prop, _qn('d', 'getetag')).text = _etag_for_event(event)
-        _qn('d', 'resourcetype'): ET.Element(_qn('d', 'resourcetype')),
+        ET.SubElement(prop, _qn('d', 'getcontenttype')).text = \
-    }
+            'text/calendar; charset=utf-8; component=VEVENT'
+        ET.SubElement(prop, _qn('d', 'resourcetype'))  # empty -> regular resource
         if include_data:
-        props[_qn('c', 'calendar-data')] = _wrap_vcalendar(cal, event)
+            ET.SubElement(prop, _qn('c', 'calendar-data')).text = _wrap_vcalendar(cal, event)
-    return _propstat_ok(href, props)
+    return _make_response(href, populate)
 
 
 def _wrap_vcalendar(cal: Calendar, event: CalendarEvent) -> str: