api: validate zero-duration posts for non-instantaneous sensors

Agent-Logs-Url: https://github.com/FlexMeasures/flexmeasures/sessions/eb04c29e-a8cf-4f7b-885f-fbe2ec4ef622

Co-authored-by: Flix6x <30658763+Flix6x@users.noreply.github.com>

Author: Copilot

documentation/changelog.rst

@@ -14,6 +14,7 @@ Infrastructure / Support
 
 Bugfixes
 -----------
+* Return a clear validation error (instead of a server ZeroDivisionError) when posting instantaneous (0-minute) data to non-instantaneous sensors via ``[POST] /sensors/(id)/data`` [see `PR #2116 <https://www.github.com/FlexMeasures/flexmeasures/pull/2116>`_]
 
 
 v0.32.0 | April 15, 2026

flexmeasures/api/common/schemas/sensor_data.py

@@ -329,10 +329,11 @@ def check_resolution_compatibility_of_sensor_data(self, data, **kwargs):
         # The event frequency is inferred by assuming sequential, equidistant values within a time interval.
         # The event resolution is assumed to be equal to the event frequency.
         inferred_resolution = data["duration"] / len(data["values"])
+        error_message = f"Resolution of {inferred_resolution} is incompatible with the sensor's required resolution of {required_resolution}."
+        if len(data["values"]) == 1 and inferred_resolution == timedelta(hours=0):
+            raise ValidationError(error_message)
         if inferred_resolution % required_resolution != timedelta(hours=0):
-            raise ValidationError(
-                f"Resolution of {inferred_resolution} is incompatible with the sensor's required resolution of {required_resolution}."
-            )
+            raise ValidationError(error_message)
 
     @validates_schema
     def check_multiple_instantaneous_values(self, data, **kwargs):

flexmeasures/api/v3_0/tests/test_sensor_data.py

@@ -187,6 +187,31 @@ def test_post_invalid_sensor_data(
     )
 
 
+@pytest.mark.parametrize(
+    "requesting_user", ["test_supplier_user_4@seita.nl"], indirect=True
+)
+def test_post_non_instantaneous_sensor_data_with_zero_duration_single_value(
+    client, setup_api_test_data, requesting_user
+):
+    post_data = make_sensor_data_request_for_gas_sensor(
+        num_values=1,
+        duration="PT0M",
+        unit="m³/h",
+    )
+    sensor = setup_api_test_data["some gas sensor"]
+
+    response = client.post(
+        url_for("SensorAPI:post_data", id=sensor.id),
+        json=post_data,
+    )
+
+    assert response.status_code == 422
+    assert (
+        "Resolution of 0:00:00 is incompatible"
+        in response.json["message"]["combined_sensor_data_description"]["_schema"][0]
+    )
+
+
 @pytest.mark.parametrize(
     "requesting_user", ["test_supplier_user_4@seita.nl"], indirect=True
 )