fix(api): handle organizations with no emissions in /sums (#693) (#1172)

GET /organizations/{id}/sums returns 500 with `{"detail": "Generic error"}`
for any organization that has no emissions logged in the requested
period. From the dashboard side this makes new or quiet organizations
look broken.

Tracing through `get_organization_detailed_sums`, the joins are outer
joins but the timestamp filter on `Emission` ends up in the WHERE clause
and so cancels them out for empty organizations. The query returns
nothing, `.first()` returns `None`, and the router hands `None` back to
FastAPI which trips the global exception handler and masks the real
shape of the response.

I kept the SQL alone and handled the empty case in the usecase, where
`get_one_organization` is already available for the metadata. When the
sums query comes back as `None` we look the organization up and return
a zero-valued `OrganizationReport`. Rebuilding the joins would be a
larger, more invasive change than what the issue asks for.

Added a parallel unit test in
`tests/api/usecase/organization/test_organization_detailed_sums.py`
that mocks both repository methods so it runs without a database. On
the unfixed code it fails on the first attribute access on `None`; on
the fixed code it passes. The existing happy-path test is unchanged.

Closes #693

Author: Hore01

carbonserver/carbonserver/api/usecases/organization/organization_sum.py

@@ -16,4 +16,27 @@ def compute_detailed_sum(
             start_date,
             end_date,
         )
-        return sums
+        if sums is not None:
+            return sums
+
+        # No emissions in the requested period. Return zeros so the dashboard
+        # still gets a valid report rather than a 500.
+        organization = self._organization_repository.get_one_organization(
+            organization_id
+        )
+        return OrganizationReport(
+            organization_id=organization.id,
+            name=organization.name,
+            description=organization.description,
+            emissions=0.0,
+            cpu_power=0.0,
+            gpu_power=0.0,
+            ram_power=0.0,
+            cpu_energy=0.0,
+            gpu_energy=0.0,
+            ram_energy=0.0,
+            energy_consumed=0.0,
+            duration=0,
+            emissions_rate=0.0,
+            emissions_count=0,
+        )

carbonserver/tests/api/usecase/organization/test_organization_detailed_sums.py

@@ -1,11 +1,13 @@
 from datetime import datetime
 from unittest import mock
+from uuid import UUID
 
 import dateutil.relativedelta
 
 from carbonserver.api.infra.repositories.repository_organizations import (
     SqlAlchemyRepository,
 )
+from carbonserver.api.schemas import Organization
 from carbonserver.api.usecases.organization.organization_sum import (
     OrganizationSumsUsecase,
 )
@@ -53,3 +55,27 @@ def test_sum_computes_for_organization_id():
         actual_organization_global_sum_by_experiment[0]["emissions"]
         == expected_emission_sum
     )
+
+
+def test_sum_returns_zero_report_when_organization_has_no_emissions():
+    """Issue #693: an organization with no emissions in the requested period
+    should get back a zero-valued report instead of triggering the global
+    "Generic error" handler.
+    """
+    repository_mock = mock.Mock(spec=SqlAlchemyRepository)
+    repository_mock.get_organization_detailed_sums.return_value = None
+    repository_mock.get_one_organization.return_value = Organization(
+        id=UUID(ORG_ID),
+        name="Quiet Org",
+        description="An organization that has not logged anything yet.",
+    )
+    usecase = OrganizationSumsUsecase(repository_mock)
+
+    report = usecase.compute_detailed_sum(ORG_ID, START_DATE, END_DATE)
+
+    assert report.organization_id == UUID(ORG_ID)
+    assert report.name == "Quiet Org"
+    assert report.emissions == 0.0
+    assert report.energy_consumed == 0.0
+    assert report.duration == 0
+    assert report.emissions_count == 0