perf: improve Array initialisation performance

src/awkward/_v2/highlevel.py

@@ -1095,7 +1095,7 @@ def __getattr__(self, where):
         Note that while fields can be accessed as attributes, they cannot be
         *assigned* as attributes. See #ak.Array.__setitem__ for more.
         """
-        if where in dir(type(self)):
+        if hasattr(type(self), where):
             return super().__getattribute__(where)
         else:
             if where in self._layout.fields:
@@ -1135,7 +1135,7 @@ def __setattr__(self, name, value):
 
         to add or modify a field.
         """
-        if name in dir(type(self)) or name.startswith("_"):
+        if name.startswith("_") or hasattr(type(self), name):
             super().__setattr__(name, value)
         elif name in self._layout.fields:
             raise ak._v2._util.error(
@@ -1817,7 +1817,7 @@ def __getattr__(self, where):
            * the field name is not a valid Python identifier or is a Python
              keyword.
         """
-        if where in dir(type(self)):
+        if hasattr(type(self), where):
             return super().__getattribute__(where)
         else:
             if where in self._layout.fields:

tests/v2/test_1511-set-attribute.py

@@ -5,7 +5,7 @@
 import numpy as np
 
 
-def test():
+def test_array():
     record = ak._v2.contents.RecordArray(
         [ak._v2.contents.NumpyArray(np.arange(10))], ["x"]
     )
@@ -19,3 +19,68 @@ def test():
 
     array._not_an_existing_attribute = 10
     assert array._not_an_existing_attribute == 10
+
+
+def test_record():
+    record = ak._v2.contents.RecordArray(
+        [ak._v2.contents.NumpyArray(np.arange(10))], ["x"]
+    )
+    array = ak._v2.Array(record)
+    record = array[0]
+
+    with pytest.raises(AttributeError):
+        record.x = 10
+
+    with pytest.raises(AttributeError):
+        record.not_an_existing_attribute = 10
+
+    record._not_an_existing_attribute = 10
+    assert record._not_an_existing_attribute == 10
+
+
+class BadBehaviorBase:
+    FIELD_STRING = "I am not a list of fields!"
+
+    @property
+    def fields(self):
+        return self.__class__.FIELD_STRING
+
+    @fields.setter
+    def fields(self, value):
+        self.__class__.FIELD_STRING = value
+
+
+class BadBehaviorArray(BadBehaviorBase, ak._v2.Array):
+    pass
+
+
+class BadBehaviorRecord(BadBehaviorBase, ak._v2.Record):
+    pass
+
+
+behavior = {("*", "bad"): BadBehaviorArray, "bad": BadBehaviorRecord}
+
+
+def test_bad_behavior_array():
+    record = ak._v2.contents.RecordArray(
+        [ak._v2.contents.NumpyArray(np.arange(10))], ["x"]
+    )
+    array = ak._v2.Array(record, with_name="bad", behavior=behavior)
+    assert isinstance(array, BadBehaviorArray)
+
+    assert array.fields == BadBehaviorArray.FIELD_STRING
+    array.fields = "yo ho ho and a bottle of rum"
+    assert array.fields == "yo ho ho and a bottle of rum"
+
+
+def test_bad_behavior_record():
+    record = ak._v2.contents.RecordArray(
+        [ak._v2.contents.NumpyArray(np.arange(10))], ["x"]
+    )
+    array = ak._v2.Array(record, with_name="bad", behavior=behavior)
+    record = array[0]
+    assert isinstance(record, BadBehaviorRecord)
+
+    assert record.fields == BadBehaviorRecord.FIELD_STRING
+    record.fields = "yo ho ho and a bottle of rum"
+    assert record.fields == "yo ho ho and a bottle of rum"