Preserve URI parameters on jCal round-trip

Author: binggao1230

news/1524.bugfix

@@ -0,0 +1 @@
+Preserve ``URI`` value parameters on a jCal round-trip. :meth:`vUri.from_jcal <icalendar.prop.uri.vUri.from_jcal>` passed the parameters positionally, but ``vUri.__new__`` takes ``encoding`` as its second positional argument, so the parameters were consumed as the encoding and dropped (for example ``ATTACH;FMTTYPE=...`` or ``CONFERENCE;FEATURE=...`` lost their parameters). They are now passed as the ``params`` keyword. Prepared with the assistance of an AI coding agent (Anthropic's Claude Opus 4.8). @gaoflow

src/icalendar/prop/uri.py

@@ -102,7 +102,7 @@ def from_jcal(cls, jcal_property: list) -> Self:
         JCalParsingError.validate_property(jcal_property, cls)
         return cls(
             jcal_property[3],
-            Parameters.from_jcal_property(jcal_property),
+            params=Parameters.from_jcal_property(jcal_property),
         )
 
     @property

src/icalendar/tests/rfc_7265_jcal/test_uri_parameters_round_trip.py

@@ -0,0 +1,74 @@
+"""Property parameters on URI-typed properties must survive a jCal round-trip.
+
+``vUri.from_jcal`` used to pass the parsed parameters as the second *positional*
+argument. Unlike every other value type, ``vUri.__new__`` takes an ``encoding``
+argument in that slot (``vUri(value, encoding, /, params=None)``), so the
+:class:`~icalendar.parser.Parameters` object was bound to ``encoding`` and
+silently discarded, leaving ``params`` at its default of ``None``.
+
+As a result parameters such as ``FMTTYPE`` (ATTACH), ``FEATURE``/``LABEL``
+(CONFERENCE) or ``RELTYPE`` (RELATED-TO) were dropped whenever a URI property was
+read back from jCal, breaking the round-trip required by :rfc:`7265`.
+"""
+
+from icalendar import Calendar, Component, Event, vUri
+from icalendar.parser import Parameters
+
+
+def _jcal_round_trip(component: Component) -> Component:
+    return Component.from_jcal(component.to_jcal())
+
+
+def test_vuri_from_jcal_keeps_parameters():
+    """The root cause: ``vUri.from_jcal`` must attach the parsed parameters."""
+    jcal_property = ["attach", {"fmttype": "text/plain"}, "uri", "http://example.com"]
+    uri = vUri.from_jcal(jcal_property)
+    assert uri.params == Parameters({"FMTTYPE": "text/plain"})
+    # The value (and the ``encoding`` slot the parameters used to be bound to)
+    # is still parsed correctly.
+    assert str(uri) == "http://example.com"
+
+
+def test_attach_fmttype_survives_jcal_round_trip():
+    event = Event()
+    event.add("UID", "1")
+    event.add(
+        "ATTACH",
+        vUri("http://example.com/report.txt", params={"FMTTYPE": "text/plain"}),
+    )
+    restored = _jcal_round_trip(event)
+    assert restored["ATTACH"].params["FMTTYPE"] == "text/plain"
+    assert b"ATTACH;FMTTYPE=text/plain:" in restored.to_ical()
+
+
+def test_conference_multiple_parameters_survive_jcal_round_trip():
+    """Several parameters on the same URI property are all preserved."""
+    event = Event()
+    event.add("UID", "1")
+    event.add(
+        "CONFERENCE",
+        vUri("tel:+1-555-0100", params={"FEATURE": "AUDIO", "LABEL": "Call in"}),
+    )
+    restored = _jcal_round_trip(event)
+    params = restored["CONFERENCE"].params
+    assert params["FEATURE"] == "AUDIO"
+    assert params["LABEL"] == "Call in"
+
+
+def test_jcal_round_trip_is_idempotent_for_uri_parameters():
+    """``to_jcal`` of the reparsed component equals the original jCal."""
+    calendar = Calendar()
+    calendar.add("VERSION", "2.0")
+    calendar.add("PRODID", "-//test//EN")
+    event = Event()
+    event.add("UID", "1")
+    event.add(
+        "ATTACH", vUri("http://example.com/x.txt", params={"FMTTYPE": "text/plain"})
+    )
+    event.add(
+        "CONFERENCE", vUri("https://chat.example.com/", params={"FEATURE": "VIDEO"})
+    )
+    calendar.add_component(event)
+
+    jcal = calendar.to_jcal()
+    assert Component.from_jcal(jcal).to_jcal() == jcal