fix: __all__ references tilecpp even when the backend is unavailable

[andrewwhitecdw]

This PR addresses the following issue in src/tilegym/ops/__init__.py: all references tilecpp even when the backend is unavailable.

Changes

• src/tilegym/ops/__init__.py: all references tilecpp even when the backend is unavailable.

Details

--- a/src/tilegym/ops/__init__.py
+++ b/src/tilegym/ops/__init__.py
@@ -1,3 +1,5 @@
-# Import CUDA Tile C++ backend if available
-if is_backend_available("tilecpp"):
-    from . import tilecpp
+# Import CUDA Tile C++ backend if available
+if is_backend_available("tilecpp"):
+    from . import tilecpp
+else:
+    tilecpp = None  # type: ignore

Tests

• tests/test_ops_init.py

--- /dev/null
+++ b/tests/test_ops_init.py
@@ -0,0 +1,21 @@
+"""Regression tests for optional tilecpp export in tilegym.ops."""
+import tilegym.ops as ops
+
+
+def test_tilecpp_name_is_always_bound():
+    """When the tilecpp backend is unavailable, the name must still exist."""
+    assert hasattr(ops, "tilecpp")
+
+
+def test_tilecpp_exported_only_when_available():
+    if ops.tilecpp is None:
+        assert "tilecpp" not in ops.__all__
+    else:
+        assert "tilecpp" in ops.__all__
+
+
+def test_star_import_does_not_raise_when_tilecpp_unavailable():
+    # ``from tilegym.ops import *`` previously raised AttributeError when
+    # tilecpp was unavailable because ``__all__`` still referenced it.
+    namespace = {}
+    exec("from tilegym.ops import *", namespace)
+    assert ("tilecpp" in namespace) == (ops.tilecpp is not None)

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