[SYCL][Graph] Improve unsupported node update error

- Include node type in error message
- Fix unit test triggering topology error instead of unsupported node type error

Author: Bensuo

sycl/source/detail/graph_impl.cpp

@@ -32,6 +32,36 @@ namespace experimental {
 namespace detail {
 
 namespace {
+/// Return a string representation of a given node_type
+inline const char *nodeTypeToString(node_type NodeType) {
+  switch (NodeType) {
+  case node_type::empty:
+    return "empty";
+  case node_type::subgraph:
+    return "subgraph";
+  case node_type::kernel:
+    return "kernel";
+  case node_type::memcpy:
+    return "memcpy";
+  case node_type::memset:
+    return "memset";
+  case node_type::memfill:
+    return "memfill";
+  case node_type::prefetch:
+    return "prefetch";
+  case node_type::memadvise:
+    return "memadvise";
+  case node_type::ext_oneapi_barrier:
+    return "ext_oneapi_barrier";
+  case node_type::host_task:
+    return "host_task";
+  case node_type::native_command:
+    return "native_command";
+  }
+  assert(false && "Unhandled node type");
+  return {};
+}
+
 /// Topologically sorts the graph in order to schedule nodes for execution.
 /// This implementation is based on Kahn's algorithm which uses a Breadth-first
 /// search approach.
@@ -1444,10 +1474,12 @@ bool exec_graph_impl::needsScheduledUpdate(
     }
 
     if (!Node->isUpdatable()) {
-      throw sycl::exception(
-          errc::invalid,
-          "Unsupported node type for update. Only kernel, host_task, "
-          "barrier and empty nodes are supported.");
+      std::string ErrorString = "node_type::";
+      ErrorString += nodeTypeToString(Node->MNodeType);
+      ErrorString +=
+          " nodes are not supported for update. Only kernel, host_task, "
+          "barrier and empty nodes are supported.";
+      throw sycl::exception(errc::invalid, ErrorString);
     }
 
     if (const auto &CG = Node->MCommandGroup;

sycl/unittests/Extensions/CommandGraph/Update.cpp

@@ -325,7 +325,7 @@ TEST_F(WholeGraphUpdateTest, UnsupportedNodeType) {
       EmptyKernel, experimental::property::node::depends_on(UpdateNodeA));
   auto UpdateNodeC = UpdateGraph.add(
       EmptyKernel, experimental::property::node::depends_on(UpdateNodeA));
-  auto UpdateNodeD = Graph.add(
+  auto UpdateNodeD = UpdateGraph.add(
       [&](handler &CGH) {
         auto Acc = Buffer.get_access(CGH);
         CGH.fill(Acc, 1);