Deprecate passing of None to jax.numpy.array

CHANGELOG.md

@@ -14,6 +14,10 @@ Remember to align the itemized text with the first line of an item within a list
 * Deprecations
   * The previously-deprecated `sym_pos` argument has been removed from
     {func}`jax.scipy.linalg.solve`. Use `assume_a='pos'` instead.
+  * Passing `None` to {func}`jax.array` or {func}`jax.asarray`, either directly or
+    within a list or tuple, is deprecated and now raises a {obj}`FutureWarning`.
+    It currently is converted to NaN, and in the future will raise a {obj}`TypeError`.
+   
 
 ## jaxlib 0.4.21
 

jax/_src/numpy/lax_numpy.py

@@ -110,6 +110,8 @@ set_printoptions = np.set_printoptions
 
 @util._wraps(np.iscomplexobj)
 def iscomplexobj(x: Any) -> bool:
+  if x is None:
+    return False
   try:
     typ = x.dtype.type
   except AttributeError:
@@ -2085,6 +2087,13 @@ def array(object: Any, dtype: DTypeLike | None = None, copy: bool = True,
     object = object.__jax_array__()
   object = tree_map(lambda leaf: leaf.__jax_array__()
                     if hasattr(leaf, "__jax_array__") else leaf, object)
+  leaves = tree_leaves(object, is_leaf=lambda x: x is None)
+  if any(leaf is None for leaf in leaves):
+    # Added Nov 16 2023
+    warnings.warn(
+      "None encountered in jnp.array(); this is currently treated as NaN. "
+      "In the future this will result in an error.",
+      FutureWarning, stacklevel=2)
     leaves = tree_leaves(object)
   if dtype is None:
     # Use lattice_result_type rather than result_type to avoid canonicalization.

tests/lax_numpy_test.py

@@ -3218,6 +3218,11 @@ class LaxBackedNumpyTests(jtu.JaxTestCase):
     with self.assertRaisesRegex(OverflowError, "Python int too large.*"):
       jnp.array([0, val])
 
+  def testArrayNoneWarning(self):
+    # TODO(jakevdp): make this an error after the deprecation period.
+    with self.assertWarnsRegex(FutureWarning, r"None encountered in jnp.array\(\)"):
+      jnp.array([0.0, None])
+
   def testIssue121(self):
     assert not np.isscalar(jnp.array(3))