[pytree][Easy] preserve dict keys in insertion order in CXX pytree (#130140)

`optree` and JAX pytree traversal the `dict` in sorted key ordering (see [Key Ordering for Dictionaries](https://github.com/metaopt/optree#key-ordering-for-dictionaries)). While in PyTorch Python pytree, we traversal the `dict` in insertion order. See also:

- #114392

This aligns the behavior of CXX pytree with Python pytree.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/130140
Approved by: https://github.com/zou3519

test/test_pytree.py

@@ -23,7 +23,6 @@ from torch.testing._internal.common_utils import (
     run_tests,
     skipIfTorchDynamo,
     subtest,
-    TEST_WITH_TORCHDYNAMO,
     TestCase,
 )
 
@@ -805,7 +804,6 @@ if "optree" in sys.modules:
             py_pytree.TreeSpec(tuple, None, []) != py_pytree.TreeSpec(list, None, []),
         )
 
-    @unittest.skipIf(TEST_WITH_TORCHDYNAMO, "Dynamo test in test_treespec_repr_dynamo.")
     def test_treespec_repr(self):
         # Check that it looks sane
         pytree = (0, [0, 0, [0]])
@@ -820,20 +818,6 @@ if "optree" in sys.modules:
             ),
         )
 
-    @unittest.skipIf(not TEST_WITH_TORCHDYNAMO, "Eager test in test_treespec_repr.")
-    def test_treespec_repr_dynamo(self):
-        # Check that it looks sane
-        pytree = (0, [0, 0, [0]])
-        _, spec = py_pytree.tree_flatten(pytree)
-        self.assertExpectedInline(
-            repr(spec),
-            """\
-TreeSpec(tuple, None, [*,
-  TreeSpec(list, None, [*,
-    *,
-    TreeSpec(list, None, [*])])])""",
-        )
-
     @parametrize(
         "spec",
         [
@@ -1365,21 +1349,12 @@ class TestCxxPytree(TestCase):
     def test_treespec_equality(self):
         self.assertEqual(cxx_pytree.LeafSpec(), cxx_pytree.LeafSpec())
 
-    @unittest.skipIf(TEST_WITH_TORCHDYNAMO, "Dynamo test in test_treespec_repr_dynamo.")
     def test_treespec_repr(self):
         # Check that it looks sane
         pytree = (0, [0, 0, [0]])
         _, spec = cxx_pytree.tree_flatten(pytree)
-        self.assertEqual(repr(spec), "PyTreeSpec((*, [*, *, [*]]), NoneIsLeaf)")
-
-    @unittest.skipIf(not TEST_WITH_TORCHDYNAMO, "Eager test in test_treespec_repr.")
-    def test_treespec_repr_dynamo(self):
-        # Check that it looks sane
-        pytree = (0, [0, 0, [0]])
-        _, spec = cxx_pytree.tree_flatten(pytree)
-        self.assertExpectedInline(
-            repr(spec),
-            "PyTreeSpec((*, [*, *, [*]]), NoneIsLeaf, namespace='torch')",
+        self.assertEqual(
+            repr(spec), "PyTreeSpec((*, [*, *, [*]]), NoneIsLeaf, namespace='torch')"
         )
 
     @parametrize(

torch/utils/_cxx_pytree.py

@@ -61,6 +61,10 @@ __all__ = [
 ]
 
 
+__TORCH_DICT_SESSION = optree.dict_insertion_ordered(True, namespace="torch")
+__TORCH_DICT_SESSION.__enter__()  # enable globally and permanently
+
+
 T = TypeVar("T")
 S = TypeVar("S")
 U = TypeVar("U")
@@ -285,20 +289,15 @@ def tree_flatten(
 
     >>> tree = {"b": (2, [3, 4]), "a": 1, "c": None, "d": 5}
     >>> tree_flatten(tree)
-    ([1, 2, 3, 4, None, 5], PyTreeSpec({'a': *, 'b': (*, [*, *]), 'c': *, 'd': *}, NoneIsLeaf))
+    ([2, 3, 4, 1, None, 5], PyTreeSpec({'b': (*, [*, *]), 'a': *, 'c': *, 'd': *}, NoneIsLeaf, namespace='torch'))
     >>> tree_flatten(1)
-    ([1], PyTreeSpec(*, NoneIsLeaf))
+    ([1], PyTreeSpec(*, NoneIsLeaf, namespace='torch'))
     >>> tree_flatten(None)
-    ([None], PyTreeSpec(*, NoneIsLeaf))
-
-    For unordered dictionaries, :class:`dict` and :class:`collections.defaultdict`, the order is
-    dependent on the **sorted** keys in the dictionary. Please use :class:`collections.OrderedDict`
-    if you want to keep the keys in the insertion order.
-
+    ([None], PyTreeSpec(*, NoneIsLeaf, namespace='torch'))
     >>> from collections import OrderedDict
     >>> tree = OrderedDict([("b", (2, [3, 4])), ("a", 1), ("c", None), ("d", 5)])
     >>> tree_flatten(tree)
-    ([2, 3, 4, 1, None, 5], PyTreeSpec(OrderedDict({'b': (*, [*, *]), 'a': *, 'c': *, 'd': *}), NoneIsLeaf))
+    ([2, 3, 4, 1, None, 5], PyTreeSpec(OrderedDict({'b': (*, [*, *]), 'a': *, 'c': *, 'd': *}), NoneIsLeaf, namespace='torch'))
 
     Args:
         tree (pytree): A pytree to flatten.
@@ -357,7 +356,7 @@ def tree_iter(
 
     >>> tree = {"b": (2, [3, 4]), "a": 1, "c": None, "d": 5}
     >>> list(tree_iter(tree))
-    [1, 2, 3, 4, None, 5]
+    [2, 3, 4, 1, None, 5]
     >>> list(tree_iter(1))
     [1]
     >>> list(tree_iter(None))
@@ -392,7 +391,7 @@ def tree_leaves(
 
     >>> tree = {"b": (2, [3, 4]), "a": 1, "c": None, "d": 5}
     >>> tree_leaves(tree)
-    [1, 2, 3, 4, None, 5]
+    [2, 3, 4, 1, None, 5]
     >>> tree_leaves(1)
     [1]
     >>> tree_leaves(None)
@@ -427,11 +426,11 @@ def tree_structure(
 
     >>> tree = {"b": (2, [3, 4]), "a": 1, "c": None, "d": 5}
     >>> tree_structure(tree)
-    PyTreeSpec({'a': *, 'b': (*, [*, *]), 'c': *, 'd': *}, NoneIsLeaf)
+    PyTreeSpec({'b': (*, [*, *]), 'a': *, 'c': *, 'd': *}, NoneIsLeaf, namespace='torch')
     >>> tree_structure(1)
-    PyTreeSpec(*, NoneIsLeaf)
+    PyTreeSpec(*, NoneIsLeaf, namespace='torch')
     >>> tree_structure(None)
-    PyTreeSpec(*, NoneIsLeaf)
+    PyTreeSpec(*, NoneIsLeaf, namespace='torch')
 
     Args:
         tree (pytree): A pytree to flatten.