Fix type checking of Union parameters (#495)

Author: leplatrem

poucave/app.py

@@ -91,10 +91,7 @@ def __init__(
                 raise ValueError(f"Unknown parameter '{param}' for '{module}'")
             # Make sure specifed value matches function param type.
             _type = self.func.__annotations__[param]
-            # Get back to original type (eg. List[str] -> list)
-            raw_type = getattr(_type, "__origin__", _type)
-            # Cast to expected type (will raise ValueError)
-            self.params[param] = raw_type(value)
+            self.params[param] = utils.cast_value(_type, value)
 
     async def run(self, cache=None, force=False) -> Tuple[Any, bool, Any, int]:
         identifier = f"{self.project}/{self.name}"

poucave/utils.py

@@ -5,7 +5,7 @@
 from contextlib import asynccontextmanager
 from datetime import datetime, timezone
 from itertools import chain
-from typing import Any, AsyncGenerator, Dict, List, Optional, Tuple
+from typing import Any, AsyncGenerator, Dict, List, Optional, Tuple, Union
 
 import aiohttp
 import backoff
@@ -215,3 +215,20 @@ async def wrapper(request):
         return web.json_response(view_result, status=status_code)
 
     return wrapper
+
+
+def cast_value(_type, value):
+    # Get back to original type (eg. List[str] -> list)
+    raw_type = getattr(_type, "__origin__", _type)
+    if raw_type is Union:
+        types = [getattr(t, "__origin__", t) for t in _type.__args__]
+    else:
+        types = [raw_type]
+    # Cast to the first compatible type.
+    while t := types.pop():
+        try:
+            return t(value)
+        except (TypeError, ValueError):
+            # Wrong parameter type. Raise if no more type to try.
+            if len(types) == 0:
+                raise

tests/conftest.py

@@ -1,5 +1,5 @@
 import os
-from typing import List
+from typing import List, Union
 
 import pytest
 import responses
@@ -16,7 +16,7 @@
 URL_PARAMETERS = ["max_age"]
 
 
-async def run(max_age: int, from_conf: int, extras: List = []):
+async def run(max_age: Union[int, float], from_conf: int, extras: List = []):
     """
     Fake check that returns the input parameters.
     Used for testing, from `tests/config.toml`.