From a059d30cad103bc6866ac264ced8feb371ba9fa1 Mon Sep 17 00:00:00 2001
From: Stef Pletinck <stef.pletinck@ugent.be>
Date: Mon, 24 Nov 2025 10:39:32 +0100
Subject: [PATCH] Fix: CORE Filter serialization

The Filter class' str method would not be called,
and the pydantic serialization logic could not deduce it.

Add an explicit field serializer to make it str.
---
 src/obelisk/asynchronous/core.py    | 10 +++++++++-
 src/tests/asynchronous/core_test.py | 12 ++++++++++++
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/obelisk/asynchronous/core.py b/src/obelisk/asynchronous/core.py
index 2007ef8..51f2089 100644
--- a/src/obelisk/asynchronous/core.py
+++ b/src/obelisk/asynchronous/core.py
@@ -24,6 +24,7 @@
     model_validator,
     SerializerFunctionWrapHandler,
     WrapSerializer,
+    field_serializer,
 )
 from typing import (
     Annotated,
@@ -157,7 +158,7 @@ class QueryParams(BaseModel):
     """List of Field Names, with their potential prefixes and suffixes, to select ordering. None user server defaults."""
     dataType: DataType | None = None
     """Data type expected to be returned, is mandatory if the `value` field is requested in the `fields` parameter"""
-    filter_: Annotated[str | Filter | None, Field(serialization_alias="filter")] = None
+    filter_: Annotated[str | Filter | None, Field(serialization_alias="filter",)] = None
     """
     Obelisk CORE handles filtering in [RSQL format](https://obelisk.pages.ilabt.imec.be/obelisk-core/query.html#rsql-format),
     to make it easier to also programatically write these filters, we provide the `obelisk.types.core.Filter` option as well.
@@ -181,6 +182,13 @@ def to_dict(self) -> dict[str, Any]:
             exclude_none=True, by_alias=True, mode="json", exclude={"dataset"}
         )
 
+    @field_serializer('filter_', mode='plain')
+    def serialize_filter(self, value: Filter | str | None) -> str | None:
+        if value is None or isinstance(value, str):
+            return value
+
+        return str(value)
+
 
 class ChunkedParams(BaseModel):
     """
diff --git a/src/tests/asynchronous/core_test.py b/src/tests/asynchronous/core_test.py
index 7f8c8c2..d7747b0 100644
--- a/src/tests/asynchronous/core_test.py
+++ b/src/tests/asynchronous/core_test.py
@@ -1,4 +1,5 @@
 from obelisk.asynchronous.core import QueryParams
+from obelisk.types.core import Filter, Comparison
 
 
 def test_query_param_serialize():
@@ -24,3 +25,14 @@ def test_comma_separate_string():
     assert data["groupBy"] == "dataset,timestamp"
     assert data["orderBy"] == "timestamp,value"
 
+
+
+def test_filter_serialize():
+    filter_ = Filter().add_and(Comparison.equal("metric", "smartphone.acceleration::number[]"), Comparison.greater_equal("timestamp", 123456))
+    q = QueryParams(
+        dataset="83989232",
+        filter_=filter_,
+        dataType="number[]",
+    )
+    dump = q.to_dict()
+    assert "filter" in dump