Allow storing float not-a-number values in MySQL database (as NULL va…

…lue)

shc/interfaces/mysql.py

@@ -3,6 +3,7 @@
 import enum
 import json
 import logging
+import math
 from typing import Optional, Type, Generic, List, Tuple, Any, Dict, Callable
 
 import aiomysql
@@ -316,7 +317,8 @@ def _get_to_mysql_converter(type_: Type[T]) -> Callable[[T], Any]:
         elif issubclass(type_, int):
             return lambda value: int(value)  # type: ignore  # type_ is equivalent to T -> int(a: int) is valid
         elif issubclass(type_, float):
-            return lambda value: float(value)  # type: ignore  # type_ is equivalent to T -> float(a: float) is valid
+            # type_ is equivalent to T -> float(a: float) is valid
+            return lambda value: None if math.isnan(value) else float(value)  # type: ignore
         elif issubclass(type_, str):
             return lambda value: str(value)
         elif issubclass(type_, enum.Enum):
@@ -328,10 +330,15 @@ def _get_to_mysql_converter(type_: Type[T]) -> Callable[[T], Any]:
     def _get_from_mysql_converter(type_: Type[T]) -> Callable[[Any], T]:
         if type_ is bool:
             return lambda x: bool(x)  # type: ignore  # type_ is equivalent to T -> type_ is bool here
-        elif type_ in (int, float, str):
+        elif type_ in (int, str):
             return lambda x: x
-        elif issubclass(type_, (bool, int, float, str, enum.Enum)):
+        elif type_ is float:
+            return lambda x: x if x is not None else float("nan")
+        elif issubclass(type_, (bool, int, str, enum.Enum)):
             return lambda value: type_(value)  # type: ignore  # type_ is equivalent to T -> type_() is an instance of T
+        elif issubclass(type_, float):
+            # type_ is equivalent to T -> type_() is an instance of T
+            return lambda value: type_(value) if value is not None else type_(float("nan"))  # type: ignore
         else:
             return lambda value: from_json(type_, json.loads(value))
 

test/interfaces/test_mysql.py

@@ -1,5 +1,6 @@
 import datetime
 import asyncio
+import math
 import unittest
 import urllib.parse
 from typing import Tuple, Type, Iterable, Dict, NamedTuple, Sequence, Any
@@ -117,6 +118,7 @@ async def _create_log_variable_with_data(self, type_: Type[T], data: Iterable[Tu
     async def test_persistence_variables(self) -> None:
         data: Sequence[Tuple[str, Sequence[Any]]] = [
             ("test_int", [5, 7]),
+            ("test_float", [3.14, float("nan")]),
             ("test_string", ["foo", "bar"]),
             ("test_tuple", [ExampleTuple(42, 3.14, "foo"), ExampleTuple(56, 0.414, "[{bar🙂😕}]")]),
         ]
@@ -125,4 +127,7 @@ async def test_persistence_variables(self) -> None:
                 variable = self.interface.persistence_variable(type(value_list[0]), variable_name)
                 for value in value_list:
                     await variable.write(value, [self])
-                self.assertEqual(value_list[-1], await variable.read())
+                if isinstance(value_list[-1], float) and math.isnan(value_list[-1]):
+                    self.assertTrue(math.isnan(await variable.read()))
+                else:
+                    self.assertEqual(value_list[-1], await variable.read())