fix: ensure that __copy__ and __deepcopy__ are enabled. (#1695)

* fix: ensure that  and  are enabled.

* Implemented all the (missing) copy/deepcopy methods.

* refactor: use private parameters where possible

* fix: use `_length` not `_zeros_length` in `RegularArray.copy()``

NB. I did think about introducing a `zeros_length` attribute, but I am concerned that we would need to take a great deal of care in handling this parameter for no good cause. Instead, we should make it such that the `length` parameter is the only externally visible one.

* refactor: replace `Content.__deepcopy__` with abstract method

This will ensure we *have* to implement this routine. Although we could use a dynamic deepcopy, it opens us up to more bugs (explicit vs implicit) and hides some of the copying logic.

* refactor: remove unneeded optional in `__deepcopy__` signature.

* fix: use `copy.deepcopy` to dispatch copying

This avoids handling deep copying in two places

* fix: `deepcopy(behavior)` in `Array/Record.__deepcopy__`

* fix: use `copy.deepcopy` in tests

Co-authored-by: Angus Hollands <goosey15@gmail.com>

src/awkward/_v2/contents/bitmaskedarray.py

@@ -39,6 +39,17 @@ def copy(
             self._nplike if nplike is unset else nplike,
         )
 
+    def __copy__(self):
+        return self.copy()
+
+    def __deepcopy__(self, memo):
+        return self.copy(
+            mask=copy.deepcopy(self._mask, memo),
+            content=copy.deepcopy(self._content, memo),
+            identifier=copy.deepcopy(self._identifier, memo),
+            parameters=copy.deepcopy(self._parameters, memo),
+        )
+
     def __init__(
         self,
         mask,

src/awkward/_v2/contents/bytemaskedarray.py

@@ -34,6 +34,17 @@ def copy(
             self._nplike if nplike is unset else nplike,
         )
 
+    def __copy__(self):
+        return self.copy()
+
+    def __deepcopy__(self, memo):
+        return self.copy(
+            mask=copy.deepcopy(self._mask, memo),
+            content=copy.deepcopy(self._content, memo),
+            identifier=copy.deepcopy(self._identifier, memo),
+            parameters=copy.deepcopy(self._parameters, memo),
+        )
+
     def __init__(
         self, mask, content, valid_when, identifier=None, parameters=None, nplike=None
     ):

src/awkward/_v2/contents/content.py

@@ -1559,16 +1559,11 @@ def with_parameter(self, key, value):
 
         return out
 
-    def __deepcopy__(self, memo=None):
-        cls = self.__class__
-        new_instance = cls.__new__(cls)
-        memo = {id(self): new_instance}
-        for k, v in self.__dict__.items():
-            if k == "_nplike":
-                new_instance._nplike = v
-            else:
-                setattr(new_instance, k, copy.deepcopy(v, memo))
-        return new_instance
+    def __copy__(self):
+        raise ak._v2._util.error(NotImplementedError)
+
+    def __deepcopy__(self, memo):
+        raise ak._v2._util.error(NotImplementedError)
 
     def _jax_flatten(self):
         from awkward._v2._connect.jax import _find_numpyarray_nodes, AuxData

src/awkward/_v2/contents/emptyarray.py

@@ -1,5 +1,7 @@
 # BSD 3-Clause License; see https://github.com/scikit-hep/awkward-1.0/blob/main/LICENSE
 
+import copy
+
 import awkward as ak
 from awkward._v2.contents.content import Content, unset
 from awkward._v2.forms.emptyform import EmptyForm
@@ -24,6 +26,15 @@ def copy(
             self._nplike if nplike is unset else nplike,
         )
 
+    def __copy__(self):
+        return self.copy()
+
+    def __deepcopy__(self, memo):
+        return self.copy(
+            identifier=copy.deepcopy(self._identifier, memo),
+            parameters=copy.deepcopy(self._parameters, memo),
+        )
+
     def __init__(self, identifier=None, parameters=None, nplike=None):
         if nplike is None:
             nplike = numpy

src/awkward/_v2/contents/indexedarray.py

@@ -30,6 +30,17 @@ def copy(
             self._nplike if nplike is unset else nplike,
         )
 
+    def __copy__(self):
+        return self.copy()
+
+    def __deepcopy__(self, memo):
+        return self.copy(
+            index=copy.deepcopy(self._index, memo),
+            content=copy.deepcopy(self._content, memo),
+            identifier=copy.deepcopy(self._identifier, memo),
+            parameters=copy.deepcopy(self._parameters, memo),
+        )
+
     def __init__(self, index, content, identifier=None, parameters=None, nplike=None):
         if not (
             isinstance(index, Index)

src/awkward/_v2/contents/indexedoptionarray.py

@@ -31,6 +31,17 @@ def copy(
             self._nplike if nplike is unset else nplike,
         )
 
+    def __copy__(self):
+        return self.copy()
+
+    def __deepcopy__(self, memo):
+        return self.copy(
+            index=copy.deepcopy(self._index, memo),
+            content=copy.deepcopy(self._content, memo),
+            identifier=copy.deepcopy(self._identifier, memo),
+            parameters=copy.deepcopy(self._parameters, memo),
+        )
+
     def __init__(self, index, content, identifier=None, parameters=None, nplike=None):
         if not (
             isinstance(index, Index)

src/awkward/_v2/contents/listarray.py

@@ -32,6 +32,18 @@ def copy(
             self._nplike if nplike is unset else nplike,
         )
 
+    def __copy__(self):
+        return self.copy()
+
+    def __deepcopy__(self, memo):
+        return self.copy(
+            starts=copy.deepcopy(self._starts, memo),
+            stops=copy.deepcopy(self._stops, memo),
+            content=copy.deepcopy(self._content, memo),
+            identifier=copy.deepcopy(self._identifier, memo),
+            parameters=copy.deepcopy(self._parameters, memo),
+        )
+
     def __init__(
         self, starts, stops, content, identifier=None, parameters=None, nplike=None
     ):

src/awkward/_v2/contents/listoffsetarray.py

@@ -30,6 +30,17 @@ def copy(
             self._nplike if nplike is unset else nplike,
         )
 
+    def __copy__(self):
+        return self.copy()
+
+    def __deepcopy__(self, memo):
+        return self.copy(
+            offsets=copy.deepcopy(self._offsets, memo),
+            content=copy.deepcopy(self._content, memo),
+            identifier=copy.deepcopy(self._identifier, memo),
+            parameters=copy.deepcopy(self._parameters, memo),
+        )
+
     def __init__(self, offsets, content, identifier=None, parameters=None, nplike=None):
         if not isinstance(offsets, Index) and offsets.dtype in (
             np.dtype(np.int32),

src/awkward/_v2/contents/numpyarray.py

@@ -1,6 +1,7 @@
 # BSD 3-Clause License; see https://github.com/scikit-hep/awkward-1.0/blob/main/LICENSE
 
 import copy
+
 import awkward as ak
 from awkward._v2.contents.content import Content, unset
 from awkward._v2.forms.numpyform import NumpyForm
@@ -27,6 +28,16 @@ def copy(
             self._nplike if nplike is unset else nplike,
         )
 
+    def __copy__(self):
+        return self.copy()
+
+    def __deepcopy__(self, memo):
+        return self.copy(
+            data=copy.deepcopy(self._data, memo),
+            identifier=copy.deepcopy(self._identifier, memo),
+            parameters=copy.deepcopy(self._parameters, memo),
+        )
+
     def __init__(self, data, identifier=None, parameters=None, nplike=None):
         if nplike is None:
             nplike = ak.nplike.of(data)
@@ -1364,14 +1375,6 @@ def _to_nplike(self, nplike):
             nplike=nplike,
         )
 
-    def __deepcopy__(self, memo=None):
-        return ak._v2.contents.NumpyArray(
-            copy.deepcopy(self._data),
-            copy.deepcopy(self._identifier),
-            copy.deepcopy(self._parameters),
-            self._nplike,
-        )
-
     def _layout_equal(self, other, index_dtype=True, numpyarray=True):
         if numpyarray:
             return (

src/awkward/_v2/contents/recordarray.py

@@ -35,6 +35,17 @@ def copy(
             self._nplike if nplike is unset else nplike,
         )
 
+    def __copy__(self):
+        return self.copy()
+
+    def __deepcopy__(self, memo):
+        return self.copy(
+            contents=[copy.deepcopy(x, memo) for x in self._contents],
+            fields=copy.deepcopy(self._fields, memo),
+            identifier=copy.deepcopy(self._identifier, memo),
+            parameters=copy.deepcopy(self._parameters, memo),
+        )
+
     def __init__(
         self,
         contents,