internal: more careful crud response process

In most cases, crud API response process assumes that there are
always two response values, which is rather uncommon. The reason of that
is internal crud wrappers [1]. This patch reworks response process a bit
to more carefully process this unusual case and to not confuse
developers.

1. https://github.com/tarantool/crud/blob/53457477974fed42351cbd87f566d11e9f7e39bb/crud/common/schema.lua#L88

Author: DifferentialOrange

tarantool/connection.py

@@ -2158,7 +2158,7 @@ def crud_insert(self, space_name: str, values: Union[tuple, list],
 
         crud_resp = call_crud(self, "crud.insert", space_name, values, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2192,7 +2192,7 @@ def crud_insert_object(self, space_name: str, values: dict,
 
         crud_resp = call_crud(self, "crud.insert_object", space_name, values, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2230,7 +2230,7 @@ def crud_insert_many(self, space_name: str, values: Union[tuple, list],
         if crud_resp[0] is not None:
             res = CrudResult(crud_resp[0])
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             errs = []
             for err in crud_resp[1]:
                 errs.append(CrudError(err))
@@ -2271,7 +2271,7 @@ def crud_insert_object_many(self, space_name: str, values: Union[tuple, list],
         if crud_resp[0] is not None:
             res = CrudResult(crud_resp[0])
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             errs = []
             for err in crud_resp[1]:
                 errs.append(CrudError(err))
@@ -2306,7 +2306,7 @@ def crud_get(self, space_name: str, key: int, opts: Optional[dict] = None) -> Cr
 
         crud_resp = call_crud(self, "crud.get", space_name, key, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2345,7 +2345,7 @@ def crud_update(self, space_name: str, key: int, operations: Optional[list] = No
 
         crud_resp = call_crud(self, "crud.update", space_name, key, operations, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2377,7 +2377,7 @@ def crud_delete(self, space_name: str, key: int, opts: Optional[dict] = None) ->
 
         crud_resp = call_crud(self, "crud.delete", space_name, key, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2411,7 +2411,7 @@ def crud_replace(self, space_name: str, values: Union[tuple, list],
 
         crud_resp = call_crud(self, "crud.replace", space_name, values, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2445,7 +2445,7 @@ def crud_replace_object(self, space_name: str, values: dict,
 
         crud_resp = call_crud(self, "crud.replace_object", space_name, values, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2483,7 +2483,7 @@ def crud_replace_many(self, space_name: str, values: Union[tuple, list],
         if crud_resp[0] is not None:
             res = CrudResult(crud_resp[0])
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             errs = []
             for err in crud_resp[1]:
                 errs.append(CrudError(err))
@@ -2524,7 +2524,7 @@ def crud_replace_object_many(self, space_name: str, values: Union[tuple, list],
         if crud_resp[0] is not None:
             res = CrudResult(crud_resp[0])
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             errs = []
             for err in crud_resp[1]:
                 errs.append(CrudError(err))
@@ -2567,7 +2567,7 @@ def crud_upsert(self, space_name: str, values: Union[tuple, list],
 
         crud_resp = call_crud(self, "crud.upsert", space_name, values, operations, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2608,7 +2608,7 @@ def crud_upsert_object(self, space_name: str, values: dict,
 
         crud_resp = call_crud(self, "crud.upsert_object", space_name, values, operations, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2646,7 +2646,7 @@ def crud_upsert_many(self, space_name: str, values_operation: Union[tuple, list]
         if crud_resp[0] is not None:
             res = CrudResult(crud_resp[0])
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             errs = []
             for err in crud_resp[1]:
                 errs.append(CrudError(err))
@@ -2687,7 +2687,7 @@ def crud_upsert_object_many(self, space_name: str, values_operation: Union[tuple
         if crud_resp[0] is not None:
             res = CrudResult(crud_resp[0])
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             errs = []
             for err in crud_resp[1]:
                 errs.append(CrudError(err))
@@ -2726,7 +2726,7 @@ def crud_select(self, space_name: str, conditions: Optional[list] = None,
 
         crud_resp = call_crud(self, "crud.select", space_name, conditions, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2758,7 +2758,7 @@ def crud_min(self, space_name: str, index_name: str, opts: Optional[dict] = None
 
         crud_resp = call_crud(self, "crud.min", space_name, index_name, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2790,7 +2790,7 @@ def crud_max(self, space_name: str, index_name: str, opts: Optional[dict] = None
 
         crud_resp = call_crud(self, "crud.max", space_name, index_name, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return CrudResult(crud_resp[0])
@@ -2819,9 +2819,7 @@ def crud_truncate(self, space_name: str, opts: Optional[dict] = None) -> bool:
 
         crud_resp = call_crud(self, "crud.truncate", space_name, opts)
 
-        # In absence of an error, crud does not give
-        # variable err as nil (as in most cases).
-        if len(crud_resp) != 1:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return crud_resp[0]
@@ -2850,9 +2848,7 @@ def crud_len(self, space_name: str, opts: Optional[dict] = None) -> int:
 
         crud_resp = call_crud(self, "crud.len", space_name, opts)
 
-        # In absence of an error, crud does not give
-        # variable err as nil (as in most cases).
-        if len(crud_resp) != 1:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return crud_resp[0]
@@ -2877,9 +2873,7 @@ def crud_storage_info(self, opts: Optional[dict] = None) -> dict:
 
         crud_resp = call_crud(self, "crud.storage_info", opts)
 
-        # In absence of an error, crud does not give
-        # variable err as nil (as in most cases).
-        if len(crud_resp) != 1:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return crud_resp[0]
@@ -2915,7 +2909,7 @@ def crud_count(self, space_name: str, conditions: Optional[list] = None,
 
         crud_resp = call_crud(self, "crud.count", space_name, conditions, opts)
 
-        if crud_resp[1] is not None:
+        if len(crud_resp) > 1 and crud_resp[1] is not None:
             raise CrudModuleError(None, CrudError(crud_resp[1]))
 
         return crud_resp[0]
@@ -2938,6 +2932,7 @@ def crud_stats(self, space_name: str = None) -> CrudResult:
 
         crud_resp = call_crud(self, "crud.stats", space_name)
 
+        # There are no errors in `crud.stats`.
         res = None
         if len(crud_resp.data[0]) > 0:
             res = CrudResult(crud_resp.data[0])