Function TEST

test/cpp/compat/torch_library_dispatch_test.cc:108–124

An operator registered only under BackendSelect must be queryable under that key and must NOT appear under CPU.

// An operator registered only under BackendSelect must be queryable under
// that key and must NOT appear under CPU.
TEST(CompatTorchDispatchTest, BackendSelectOnlyRegistration) {
  const auto qname = "compat_dispatch_test_lib::backend_select_only";
  auto* op = torch::OperatorRegistry::instance().find_operator(qname);
  ASSERT_NE(op, nullptr);

  EXPECT_EQ(op->implementations.find(c10::DispatchKey::CPU),
            op->implementations.end());

  auto bs_it = op->implementations.find(c10::DispatchKey::BackendSelect);
  ASSERT_NE(bs_it, op->implementations.end());

  torch::FunctionArgs args;
  args.add_arg(torch::IValue(int64_t(32)));
  auto result = bs_it->second.call_with_args(args);
  ASSERT_TRUE(result.get_value().is_int());
  EXPECT_EQ(result.get_value().to_int(), 42);  // 32 + 10
}

// When CPU and BackendSelect are both registered, the priority lookup must
// pick CPU (higher priority in get_op_with_args).