Add deprecation flag on base backend.

Update unit tests
Lint

Author: FlorianDeconinck

src/gt4py/cartesian/backend/base.py

@@ -228,6 +228,7 @@ def generate_bindings(self, language_name: str) -> Dict[str, Union[str, Dict]]:
 
 class BaseBackend(Backend):
     MODULE_GENERATOR_CLASS: ClassVar[Type["BaseModuleGenerator"]]
+    deprecated: bool = False
 
     def load(self) -> Optional[Type["StencilObject"]]:
         build_info = self.builder.options.build_info

src/gt4py/cartesian/backend/cuda_backend.py

@@ -147,12 +147,14 @@ class CudaBackend(BaseGTBackend, CLIBackendMixin):
     PYEXT_GENERATOR_CLASS = CudaExtGenerator  # type: ignore
     MODULE_GENERATOR_CLASS = CUDAPyExtModuleGenerator
     GT_BACKEND_T = "gpu"
+    deprecated = not GT4PY_GTC_CUDA_USE
 
     def generate_extension(self, **kwargs: Any) -> Tuple[str, str]:
         return self.make_extension(stencil_ir=self.builder.gtir, uses_cuda=True)
 
     def generate(self) -> Type["StencilObject"]:
-        if GT4PY_GTC_CUDA_USE:
+        # We push for hard deprecation here by raising by default and warning if use has been forced.
+        if not self.deprecated:
             warnings.warn(
                 "cuda backend is deprecated, feature developed after February 2024 will not be available",
                 DeprecationWarning,
@@ -161,7 +163,7 @@ def generate(self) -> Type["StencilObject"]:
         else:
             raise NotImplementedError(
                 "cuda backend is no longer maintained (February 2024)."
-                "You can still force the use of the backend by defining GT4PY_GTC_CUDA_USE=1"
+                "You can still force the use of the backend by defining GT4PY_GTC_CUDA_USE=1."
             )
 
         self.check_options(self.builder.options)

src/gt4py/cartesian/backend/gtc_common.py

@@ -286,7 +286,10 @@ def make_extension(
         gt_pyext_sources: Dict[str, Any]
         if not self.builder.options._impl_opts.get("disable-code-generation", False):
             gt_pyext_files = self.make_extension_sources(stencil_ir=stencil_ir)
-            gt_pyext_sources = {**gt_pyext_files["computation"], **gt_pyext_files["bindings"]}
+            gt_pyext_sources = {
+                **gt_pyext_files["computation"],
+                **gt_pyext_files["bindings"],
+            }
         else:
             # Pass NOTHING to the self.builder means try to reuse the source code files
             gt_pyext_files = {}

tests/cartesian_tests/definitions.py

@@ -44,7 +44,7 @@ def _get_backends_with_storage_info(storage_info_kind: str):
     for name in _ALL_BACKEND_NAMES:
         backend = gt4pyc.backend.from_name(name)
         if backend is not None:
-            if backend.storage_info["device"] == storage_info_kind:
+            if backend.storage_info["device"] == storage_info_kind and not backend.deprecated:
                 res.append(_backend_name_as_param(name))
     return res
 

tests/cartesian_tests/unit_tests/backend_tests/test_backend.py

@@ -48,7 +48,11 @@ def stencil_def(
             out = pa * fa + pb * fb - pc * fc  # type: ignore  # noqa
 
 
-field_info_val = {0: ("out", "fa"), 1: ("out", "fa", "fb"), 2: ("out", "fa", "fb", "fc")}
+field_info_val = {
+    0: ("out", "fa"),
+    1: ("out", "fa", "fb"),
+    2: ("out", "fa", "fb", "fc"),
+}
 parameter_info_val = {0: ("pa",), 1: ("pa", "pb"), 2: ("pa", "pb", "pc")}
 unreferenced_val = {0: ("pb", "fb", "pc", "fc"), 1: ("pc", "fc"), 2: ()}
 
@@ -168,5 +172,23 @@ def test_toolchain_profiling(backend_name: str, mode: int, rebuild: bool):
         assert build_info["load_time"] > 0.0
 
 
+@pytest.mark.parametrize("backend_name", ["cuda"])
+def test_deprecation_gtc_cuda(backend_name: str):
+    # Default deprecation, raise an error
+    build_info: Dict[str, Any] = {}
+    builder = (
+        StencilBuilder(cast(StencilFunc, stencil_def))
+        .with_backend(backend_name)
+        .with_externals({"MODE": 2})
+        .with_options(
+            name=stencil_def.__name__,
+            module=stencil_def.__module__,
+            build_info=build_info,
+        )
+    )
+    with pytest.raises(NotImplementedError):
+        builder.build()
+
+
 if __name__ == "__main__":
     pytest.main([__file__])