From 374212ad8313f86b9d993134ecb98ad3d62281db Mon Sep 17 00:00:00 2001
From: crusaderky <crusaderky@gmail.com>
Date: Wed, 23 Apr 2025 18:50:31 +0100
Subject: [PATCH] [WIP] ENH: dask+cupy, dask+sparse etc. namespaces

---
 array_api_compat/common/_helpers.py     | 25 ++++++++++---
 array_api_compat/dask/array/__init__.py |  1 +
 array_api_compat/dask/array/_aliases.py | 13 ++++++-
 array_api_compat/dask/array/_meta.py    | 49 +++++++++++++++++++++++++
 4 files changed, 81 insertions(+), 7 deletions(-)
 create mode 100644 array_api_compat/dask/array/_meta.py

diff --git a/array_api_compat/common/_helpers.py b/array_api_compat/common/_helpers.py
index 77175d0d..a518b126 100644
--- a/array_api_compat/common/_helpers.py
+++ b/array_api_compat/common/_helpers.py
@@ -397,7 +397,9 @@ def is_dask_namespace(xp: Namespace) -> bool:
     """
     Returns True if `xp` is a Dask namespace.
 
-    This includes both ``dask.array`` itself and the version wrapped by array-api-compat.
+    This includes ``dask.array`` itself, the version wrapped by array-api-compat,
+    and the bespoke namespaces generated by
+    ``array_api_compat.dask.array.wrap_namespace``.
 
     See Also
     --------
@@ -411,7 +413,13 @@ def is_dask_namespace(xp: Namespace) -> bool:
     is_pydata_sparse_namespace
     is_array_api_strict_namespace
     """
-    return xp.__name__ in {"dask.array", _compat_module_name() + ".dask.array"}
+    da_compat_name = _compat_module_name() + '.dask.array'
+    name = xp.__name__
+    return (
+        name in {'dask.array', da_compat_name} 
+        or name.startswith(da_compat_name + '.')
+        and name[len(da_compat_name) + 1:] not in ("linalg", "fft")
+    )
 
 
 def is_jax_namespace(xp: Namespace) -> bool:
@@ -597,9 +605,16 @@ def your_function(x, y):
         elif is_dask_array(x):
             if _use_compat:
                 _check_api_version(api_version)
-                from ..dask import array as dask_namespace
-
-                namespaces.add(dask_namespace)
+                from ..dask.array import wrap_namespace
+
+                # The meta-namespace is only used to generate the meta-array, so it
+                # would be useless to create a namespace such as e.g.
+                # array_api_compat.dask.array.array_api_compat.cupy.
+                # It would get worse once you vendor array-api-compat!
+                # So keep it clean with array_api_compat.dask.array.cupy.
+                mxp = array_namespace(x._meta, use_compat=False)
+                xp = wrap_namespace(mxp)
+                namespaces.add(xp)
             else:
                 import dask.array as da
 
diff --git a/array_api_compat/dask/array/__init__.py b/array_api_compat/dask/array/__init__.py
index 1e47b960..fec80197 100644
--- a/array_api_compat/dask/array/__init__.py
+++ b/array_api_compat/dask/array/__init__.py
@@ -4,6 +4,7 @@
 
 # These imports may overwrite names from the import * above.
 from ._aliases import *  # noqa: F403
+from ._meta import wrap_namespace # noqa: F401
 
 __array_api_version__: Final = "2024.12"
 
diff --git a/array_api_compat/dask/array/_aliases.py b/array_api_compat/dask/array/_aliases.py
index 9687a9cd..86704e77 100644
--- a/array_api_compat/dask/array/_aliases.py
+++ b/array_api_compat/dask/array/_aliases.py
@@ -152,6 +152,7 @@ def asarray(
     dtype: DType | None = None,
     device: Device | None = None,
     copy: py_bool | None = None,
+    like: Array | None = None,
     **kwargs: object,
 ) -> Array:
     """
@@ -168,7 +169,11 @@ def asarray(
             if copy is False:
                 raise ValueError("Unable to avoid copy when changing dtype")
             obj = obj.astype(dtype)
-        return obj.copy() if copy else obj  # pyright: ignore[reportAttributeAccessIssue]
+        if copy:
+            obj = obj.copy()
+        if like is not None:
+            obj = da.asarray(obj, like=like)
+        return obj
 
     if copy is False:
         raise NotImplementedError(
@@ -177,7 +182,11 @@ def asarray(
 
     # copy=None to be uniform across dask < 2024.12 and >= 2024.12
     # see https://github.com/dask/dask/pull/11524/
-    obj = np.array(obj, dtype=dtype, copy=True)
+    if like is not None:
+        mxp = array_namespace(like)
+        obj = mxp.asarray(obj, dtype=dtype, copy=True)
+    else:
+        obj = np.array(obj, dtype=dtype, copy=True)
     return da.from_array(obj)
 
 
diff --git a/array_api_compat/dask/array/_meta.py b/array_api_compat/dask/array/_meta.py
new file mode 100644
index 00000000..9365ad2a
--- /dev/null
+++ b/array_api_compat/dask/array/_meta.py
@@ -0,0 +1,49 @@
+import functools
+import sys
+import types
+
+from ...common._helpers import is_numpy_namespace
+from ...common._typing import Namespace
+
+__all__ = ['wrap_namespace']
+
+
+def wrap_namespace(xp: Namespace) -> Namespace:
+    """Create a bespoke Dask namespace that wraps around another namespace.
+
+    Parameters
+    ----------
+    xp : namespace
+        Namespace to be wrapped by Dask
+
+    Returns
+    -------
+    namespace :
+        A module object that duplicates array_api_compat.dask.array, with the
+        difference that all creation functions will create an array with the same
+        meta namespace as the input.
+    """
+    from .. import array as da_compat
+
+    if is_numpy_namespace(xp):
+        return da_compat
+
+    mod_name = f'{da_compat.__name__}.{xp.__name__}'
+    try:
+        return sys.modules[mod_name]
+    except KeyError:
+        pass
+
+    mod = types.ModuleType(mod_name)
+    sys.modules[mod_name] = mod
+
+    meta = xp.empty(())
+    for name, v in da_compat.__dict__.items():
+        if name.startswith('_'):
+            continue
+        if name in {'arange',  'asarray', 'empty', 'eye', 'from_dlpack',
+                    'full', 'linspace', 'ones', 'zeros'}:
+            v = functools.wraps(v)(functools.partial(v, like=meta))
+        setattr(mod, name, v)
+
+    return mod