ENH: lazy_xp_function namespaces support

Author: crusaderky

src/array_api_extra/testing.py

@@ -57,9 +57,8 @@ def lazy_xp_function(  # type: ignore[no-any-explicit]
     """
     Tag a function to be tested on lazy backends.
 
-    Tag a function, which must be imported in the test module globals, so that when any
-    tests defined in the same module are executed with ``xp=jax.numpy`` the function is
-    replaced with a jitted version of itself, and when it is executed with
+    Tag a function so that when any tests are executed with ``xp=jax.numpy`` the
+    function is replaced with a jitted version of itself, and when it is executed with
     ``xp=dask.array`` the function will raise if it attempts to materialize the graph.
     This will be later expanded to provide test coverage for other lazy backends.
 
@@ -121,19 +120,59 @@ def test_myfunc(xp):
 
     Notes
     -----
-    A test function can circumvent this monkey-patching system by calling `func` as an
-    attribute of the original module. You need to sanitize your code to make sure this
-    does not happen.
+    In order for this tag to be effective, the test function must be imported into the
+    test module globals without namespace; alternatively its namespace must be declared
+    in a ``lazy_xp_modules`` list in the test module globals.
 
-    Example::
+    Example 1::
 
-      import mymodule from mymodule import myfunc
+      from mymodule import myfunc
 
       lazy_xp_function(myfunc)
 
       def test_myfunc(xp):
-          a = xp.asarray([1, 2]) b = myfunc(a)  # This is jitted when xp=jax.numpy c =
-          mymodule.myfunc(a)  # This is not
+          x = myfunc(xp.asarray([1, 2]))
+
+    Example 2::
+
+      import mymodule
+
+      lazy_xp_modules = [mymodule]
+      lazy_xp_function(mymodule.myfunc)
+
+      def test_myfunc(xp):
+          x = mymodule.myfunc(xp.asarray([1, 2]))
+
+    A test function can circumvent this monkey-patching system by using a namespace
+    outside of the two above patterns. You need to sanitize your code to make sure this
+    only happens intentionally.
+
+    Example 1::
+
+      import mymodule
+      from mymodule import myfunc
+
+      lazy_xp_function(myfunc)
+
+      def test_myfunc(xp):
+          a = xp.asarray([1, 2])
+          b = myfunc(a)  # This is jitted when xp=jax.numpy
+          c = mymodule.myfunc(a)  # This is not
+
+    Example 2::
+
+      import mymodule
+
+      class naked:
+          myfunc = mymodule.myfunc
+
+      lazy_xp_modules = [mymodule]
+      lazy_xp_function(mymodule.myfunc)
+
+      def test_myfunc(xp):
+          a = xp.asarray([1, 2])
+          b = mymodule.myfunc(a)  # This is jitted when xp=jax.numpy
+          c = naked.myfunc(a)  # This is not
     """
     tags = {
         "allow_dask_compute": allow_dask_compute,
@@ -154,11 +193,13 @@ def patch_lazy_xp_functions(
     Test lazy execution of functions tagged with :func:`lazy_xp_function`.
 
     If ``xp==jax.numpy``, search for all functions which have been tagged with
-    :func:`lazy_xp_function` in the globals of the module that defines the current test
+    :func:`lazy_xp_function` in the globals of the module that defines the current test,
+    as well as in the ``lazy_xp_modules`` list in the globals of the same module,
     and wrap them with :func:`jax.jit`. Unwrap them at the end of the test.
 
     If ``xp==dask.array``, wrap the functions with a decorator that disables
-    ``compute()`` and ``persist()``.
+    ``compute()`` and ``persist()`` and ensures that exceptions and warnings are raised
+    eagerly.
 
     This function should be typically called by your library's `xp` fixture that runs
     tests on multiple backends::
@@ -184,29 +225,33 @@ def xp(request, monkeypatch):
     lazy_xp_function : Tag a function to be tested on lazy backends.
     pytest.FixtureRequest : `request` test function parameter.
     """
-    globals_ = cast("dict[str, Any]", request.module.__dict__)  # type: ignore[no-any-explicit]
-
-    def iter_tagged() -> Iterator[tuple[str, Callable[..., Any], dict[str, Any]]]:  # type: ignore[no-any-explicit]
-        for name, func in globals_.items():
-            tags: dict[str, Any] | None = None  # type: ignore[no-any-explicit]
-            with contextlib.suppress(AttributeError):
-                tags = func._lazy_xp_function  # pylint: disable=protected-access
-            if tags is None:
-                with contextlib.suppress(KeyError, TypeError):
-                    tags = _ufuncs_tags[func]
-            if tags is not None:
-                yield name, func, tags
+    mod = cast(ModuleType, request.module)
+    mods = [mod, *cast(list[ModuleType], getattr(mod, "lazy_xp_modules", []))]
+
+    def iter_tagged() -> (  # type: ignore[no-any-explicit]
+        Iterator[tuple[ModuleType, str, Callable[..., Any], dict[str, Any]]]
+    ):
+        for mod in mods:
+            for name, func in mod.__dict__.items():
+                tags: dict[str, Any] | None = None  # type: ignore[no-any-explicit]
+                with contextlib.suppress(AttributeError):
+                    tags = func._lazy_xp_function  # pylint: disable=protected-access
+                if tags is None:
+                    with contextlib.suppress(KeyError, TypeError):
+                        tags = _ufuncs_tags[func]
+                if tags is not None:
+                    yield mod, name, func, tags
 
     if is_dask_namespace(xp):
-        for name, func, tags in iter_tagged():
+        for mod, name, func, tags in iter_tagged():
             n = tags["allow_dask_compute"]
             wrapped = _dask_wrap(func, n)
-            monkeypatch.setitem(globals_, name, wrapped)
+            monkeypatch.setattr(mod, name, wrapped)
 
     elif is_jax_namespace(xp):
         import jax
 
-        for name, func, tags in iter_tagged():
+        for mod, name, func, tags in iter_tagged():
             if tags["jax_jit"]:
                 # suppress unused-ignore to run mypy in -e lint as well as -e dev
                 wrapped = cast(  # type: ignore[no-any-explicit]
@@ -217,7 +262,7 @@ def iter_tagged() -> Iterator[tuple[str, Callable[..., Any], dict[str, Any]]]:
                         static_argnames=tags["static_argnames"],
                     ),
                 )
-                monkeypatch.setitem(globals_, name, wrapped)
+                monkeypatch.setattr(mod, name, wrapped)
 
 
 class CountingDaskScheduler(SchedulerGetCallable):

tests/test_testing.py

@@ -108,6 +108,7 @@ def non_materializable(x: Array) -> Array:
     and it will trigger an expensive computation in dask.
     """
     xp = array_namespace(x)
+    # Crashes inside jax.jit
     # On dask, this triggers two computations of the whole graph
     if xp.any(x < 0.0) or xp.any(x > 10.0):
         msg = "Values must be in the [0, 10] range"
@@ -261,3 +262,39 @@ def test_lazy_xp_function_eagerly_raises(da: ModuleType):
     x = da.arange(3)
     with pytest.raises(ValueError, match="Hello world"):
         dask_raises(x)
+
+
+class Wrapped:
+    def f(x: Array) -> Array:  # noqa: N805  # pyright: ignore[reportSelfClsParameterName]
+        xp = array_namespace(x)
+        # Crash in jax.jit and trigger compute() on dask
+        if not xp.all(x):
+            msg = "Values must be non-zero"
+            raise ValueError(msg)
+        return x
+
+
+class Naked:
+    f = Wrapped.f  # pyright: ignore[reportUnannotatedClassAttribute]
+
+
+lazy_xp_function(Wrapped.f)
+lazy_xp_modules = [Wrapped]
+
+
+def test_lazy_xp_modules(xp: ModuleType, library: Backend):
+    x = xp.asarray([1.0, 2.0])
+    y = Naked.f(x)
+    xp_assert_equal(y, x)
+
+    if library is Backend.JAX:
+        with pytest.raises(
+            TypeError, match="Attempted boolean conversion of traced array"
+        ):
+            Wrapped.f(x)
+    elif library is Backend.DASK:
+        with pytest.raises(AssertionError, match=r"dask\.compute"):
+            Wrapped.f(x)
+    else:
+        y = Wrapped.f(x)
+        xp_assert_equal(y, x)