Fix manual verification of elements_ratios

optimade/models/structures.py

@@ -612,7 +612,7 @@ def elements_must_be_alphabetical(cls, v):
     @validator("elements_ratios", whole=True)
     def ratios_must_sum_to_one(cls, v):
         assert (
-            abs(sum(v) - 1) < EPS
+            abs(sum(v) - 1) <= EPS
         ), f"elements_ratios MUST sum to 1 within floating point accuracy. It sums to: {sum(v)}"
         return v
 

optimade/models/toplevel.py

@@ -164,7 +164,7 @@ class ResponseMeta(Meta):
 
 class StructureResponseOne(Success):
     meta: ResponseMeta = Schema(...)
-    data: Union[StructureResource, Dict[str, Any]] = Schema(...)
+    data: Union[StructureResource, Dict[str, Any], None] = Schema(...)
 
 
 class StructureResponseMany(Success):

optimade/server/entry_collections.py

@@ -106,7 +106,7 @@ def find(
         else:
             more_data_available = False
             data_available = self.count(**criteria)
-            if data_available != 1:
+            if data_available > 1:
                 raise HTTPException(
                     status_code=404,
                     detail=f"Instead of a single entry, {data_available} entries were found",
@@ -121,7 +121,7 @@ def find(
             results.append(self.resource_cls(**StructureMapper.map_back(doc)))
 
         if isinstance(params, SingleEntryQueryParams):
-            results = results[0]
+            results = results[0] if results else None
 
         return results, more_data_available, data_available, all_fields - fields
 

optimade/server/main.py

@@ -240,11 +240,14 @@ def get_single_structure(
     links = ToplevelLinks(next=None)
     if fields and results is not None:
         results = handle_response_fields(results, fields)[0]
+
+    data_returned = 1 if results else 0
+
     return StructureResponseOne(
         links=links,
         data=results,
         meta=meta_values(
-            str(request.url), data_available, data_available, more_data_available
+            str(request.url), data_returned, data_available, more_data_available
         ),
     )
 

optimade/server/tests/test_server.py

@@ -140,3 +140,14 @@ def test_structures_endpoint_data(self):
         self.assertTrue(
             "_exmpl__mp_chemsys" in self.json_response["data"]["attributes"]
         )
+
+
+class SingleStructureEndpointEmptyTest(EndpointTests, unittest.TestCase):
+
+    test_id = "non_existent_id"
+    request_str = f"/structures/{test_id}"
+    response_cls = StructureResponseOne
+
+    def test_structures_endpoint_data(self):
+        self.assertTrue("data" in self.json_response)
+        self.assertEqual(self.json_response["data"], None)