Validate aggregation callables accept single positional argument

Author: shuofengzhang

neat/aggregations.py

@@ -49,7 +49,7 @@ class InvalidAggregationFunction(TypeError):
     pass
 
 
-def validate_aggregation(function):  # TODO: Recognize when need `reduce`
+def validate_aggregation(function):
     if not callable(function):
         raise InvalidAggregationFunction("A callable object is required.")
 
@@ -60,17 +60,12 @@ def validate_aggregation(function):  # TODO: Recognize when need `reduce`
             return
         raise InvalidAggregationFunction("Unable to inspect aggregation callable signature.") from exc
 
-    accepts_positional = any(
-        parameter.kind in (
-            inspect.Parameter.POSITIONAL_ONLY,
-            inspect.Parameter.POSITIONAL_OR_KEYWORD,
-            inspect.Parameter.VAR_POSITIONAL,
-        )
-        for parameter in signature.parameters.values()
-    )
-
-    if not accepts_positional:
-        raise InvalidAggregationFunction("A function taking at least one positional argument is required")
+    try:
+        signature.bind(object())
+    except TypeError as exc:
+        raise InvalidAggregationFunction(
+            "A function taking a single positional argument is required"
+        ) from exc
 
 
 class AggregationFunctionSet:

tests/test_aggregation.py

@@ -91,6 +91,10 @@ def keyword_only_function(*, items):
     return sum(items)
 
 
+def two_argument_function(items, scale):
+    return sum(items) * scale
+
+
 def test_function_set():
     s = aggregations.AggregationFunctionSet()
     assert s.get('sum') is not None
@@ -165,6 +169,21 @@ def test_bad_add3():
         raise Exception("Should have had a TypeError/derived for keyword_only_function")
 
 
+def test_bad_add4():
+    local_dir = os.path.dirname(__file__)
+    config_path = os.path.join(local_dir, 'test_configuration')
+    config = neat.Config(neat.DefaultGenome, neat.DefaultReproduction,
+                         neat.DefaultSpeciesSet, neat.DefaultStagnation,
+                         config_path)
+
+    try:
+        config.genome_config.add_aggregation('two_argument_function', two_argument_function)
+    except TypeError:
+        pass
+    else:
+        raise Exception("Should have had a TypeError/derived for two_argument_function")
+
+
 if __name__ == '__main__':
     test_sum()
     test_product()