fix(deck): Always preserve fields in update_card for partial updates

The Deck PUT API is a full replacement, not a partial update.
Previously, title and description were conditionally sent, causing:
- 400 errors when title not provided (it's required)
- Description being cleared when not explicitly set

Now all required fields (title, type, owner) and description are
always included in the payload using current card values when not
explicitly provided. This matches the existing pattern for type/owner.

Also simplified owner extraction since DeckCard.validate_owner
already ensures it's always a string.

Fixes #452

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

nextcloud_mcp_server/client/deck.py

@@ -285,28 +285,23 @@ class DeckClient(BaseNextcloudClient):
         archived: Optional[bool] = None,
         done: Optional[str] = None,
     ) -> None:
-        # First, get the current card to use existing values for required fields
+        # Deck PUT API is a full replacement - all required fields must be sent.
+        # Fetch current card to preserve values for fields not being updated.
         current_card = await self.get_card(board_id, stack_id, card_id)
 
-        json_data = {}
-        if title is not None:
-            json_data["title"] = title
-        if description is not None:
-            json_data["description"] = description
-        # Type is required by the API, use provided or keep current
-        json_data["type"] = type if type is not None else current_card.type
-        # Owner is required by the API, use provided or keep current
-        json_data["owner"] = (
-            owner
-            if owner is not None
-            else (
-                current_card.owner
-                if isinstance(current_card.owner, str)
-                else current_card.owner.uid
-                if hasattr(current_card.owner, "uid")
-                else current_card.owner.primaryKey
-            )
-        )
+        # Build payload with required fields always included
+        json_data = {
+            # Title is required by the API
+            "title": title if title is not None else current_card.title,
+            # Type is required by the API
+            "type": type if type is not None else current_card.type,
+            # Owner is required by the API (model validator ensures it's a string)
+            "owner": owner if owner is not None else current_card.owner,
+            # Description must be sent to preserve it (PUT clears omitted fields)
+            "description": description
+            if description is not None
+            else (current_card.description or ""),
+        }
         if order is not None:
             json_data["order"] = order
         if duedate is not None:

tests/client/deck/test_deck_update_card_api.py

@@ -0,0 +1,194 @@
+"""
+Integration tests for DeckClient.update_card API behavior.
+
+These tests define the EXPECTED behavior for partial card updates:
+- Only fields explicitly passed should be modified
+- All other fields should be preserved unchanged
+
+Related issues:
+- nextcloud-mcp-server #452: DeckClient.update_card partial update bugs
+- deck #3127: REST API Docs: missing parameter in "update cards"
+- deck #4106: Provide a working example of API usage to update a cards details
+"""
+
+import pytest
+
+pytestmark = [pytest.mark.integration]
+
+
+@pytest.fixture
+async def deck_test_card(nc_client):
+    """Create a board, stack, and card for testing, cleanup after."""
+    board = await nc_client.deck.create_board("Test Update Card API", "FF0000")
+    stack = await nc_client.deck.create_stack(board.id, "Test Stack", 1)
+    card = await nc_client.deck.create_card(
+        board.id,
+        stack.id,
+        "Original Title",
+        type="plain",
+        description="Original description",
+    )
+
+    yield {
+        "board_id": board.id,
+        "stack_id": stack.id,
+        "card_id": card.id,
+        "card": card,
+    }
+
+    # Cleanup
+    await nc_client.deck.delete_board(board.id)
+
+
+class TestDeckClientUpdateCard:
+    """
+    Test DeckClient.update_card() partial update behavior.
+
+    Expected: Only explicitly provided fields are updated, all others preserved.
+    """
+
+    async def test_update_title_only_preserves_description(
+        self, nc_client, deck_test_card
+    ):
+        """Updating only the title should preserve the description."""
+        await nc_client.deck.update_card(
+            board_id=deck_test_card["board_id"],
+            stack_id=deck_test_card["stack_id"],
+            card_id=deck_test_card["card_id"],
+            title="New Title",
+        )
+
+        updated = await nc_client.deck.get_card(
+            deck_test_card["board_id"],
+            deck_test_card["stack_id"],
+            deck_test_card["card_id"],
+        )
+        assert updated.title == "New Title"
+        assert updated.description == "Original description"
+
+    async def test_update_description_only(self, nc_client, deck_test_card):
+        """Updating only the description should work and preserve other fields."""
+        await nc_client.deck.update_card(
+            board_id=deck_test_card["board_id"],
+            stack_id=deck_test_card["stack_id"],
+            card_id=deck_test_card["card_id"],
+            description="New description only",
+        )
+
+        updated = await nc_client.deck.get_card(
+            deck_test_card["board_id"],
+            deck_test_card["stack_id"],
+            deck_test_card["card_id"],
+        )
+        assert updated.title == "Original Title"
+        assert updated.description == "New description only"
+
+    async def test_update_title_and_description(self, nc_client, deck_test_card):
+        """Updating title and description together should work."""
+        await nc_client.deck.update_card(
+            board_id=deck_test_card["board_id"],
+            stack_id=deck_test_card["stack_id"],
+            card_id=deck_test_card["card_id"],
+            title="New Title",
+            description="New description",
+        )
+
+        updated = await nc_client.deck.get_card(
+            deck_test_card["board_id"],
+            deck_test_card["stack_id"],
+            deck_test_card["card_id"],
+        )
+        assert updated.title == "New Title"
+        assert updated.description == "New description"
+
+    async def test_update_duedate_only(self, nc_client, deck_test_card):
+        """Updating only the duedate should work and preserve other fields."""
+        await nc_client.deck.update_card(
+            board_id=deck_test_card["board_id"],
+            stack_id=deck_test_card["stack_id"],
+            card_id=deck_test_card["card_id"],
+            duedate="2025-12-31T23:59:59+00:00",
+        )
+
+        updated = await nc_client.deck.get_card(
+            deck_test_card["board_id"],
+            deck_test_card["stack_id"],
+            deck_test_card["card_id"],
+        )
+        assert updated.title == "Original Title"
+        assert updated.description == "Original description"
+        assert updated.duedate is not None
+
+    async def test_update_archived_only(self, nc_client, deck_test_card):
+        """Updating only the archived status should work and preserve other fields."""
+        await nc_client.deck.update_card(
+            board_id=deck_test_card["board_id"],
+            stack_id=deck_test_card["stack_id"],
+            card_id=deck_test_card["card_id"],
+            archived=True,
+        )
+
+        updated = await nc_client.deck.get_card(
+            deck_test_card["board_id"],
+            deck_test_card["stack_id"],
+            deck_test_card["card_id"],
+        )
+        assert updated.title == "Original Title"
+        assert updated.description == "Original description"
+        assert updated.archived is True
+
+    async def test_update_order_only(self, nc_client, deck_test_card):
+        """Updating only the order should work and preserve other fields."""
+        await nc_client.deck.update_card(
+            board_id=deck_test_card["board_id"],
+            stack_id=deck_test_card["stack_id"],
+            card_id=deck_test_card["card_id"],
+            order=99,
+        )
+
+        updated = await nc_client.deck.get_card(
+            deck_test_card["board_id"],
+            deck_test_card["stack_id"],
+            deck_test_card["card_id"],
+        )
+        assert updated.title == "Original Title"
+        assert updated.description == "Original description"
+        assert updated.order == 99
+
+    async def test_update_preserves_type(self, nc_client, deck_test_card):
+        """Type should be preserved when not explicitly changed."""
+        original = deck_test_card["card"]
+
+        await nc_client.deck.update_card(
+            board_id=deck_test_card["board_id"],
+            stack_id=deck_test_card["stack_id"],
+            card_id=deck_test_card["card_id"],
+            title="Changed Title",
+        )
+
+        updated = await nc_client.deck.get_card(
+            deck_test_card["board_id"],
+            deck_test_card["stack_id"],
+            deck_test_card["card_id"],
+        )
+        assert updated.type == original.type
+        assert updated.description == "Original description"
+
+    async def test_update_preserves_owner(self, nc_client, deck_test_card):
+        """Owner should be preserved when not explicitly changed."""
+        original = deck_test_card["card"]
+
+        await nc_client.deck.update_card(
+            board_id=deck_test_card["board_id"],
+            stack_id=deck_test_card["stack_id"],
+            card_id=deck_test_card["card_id"],
+            title="Changed Title",
+        )
+
+        updated = await nc_client.deck.get_card(
+            deck_test_card["board_id"],
+            deck_test_card["stack_id"],
+            deck_test_card["card_id"],
+        )
+        assert updated.owner == original.owner
+        assert updated.description == "Original description"