[BugFix][C++] Check is not nullptr before calling ToString and fix empty prefix bug

cpp/include/gar/fwd.h

@@ -114,7 +114,7 @@ std::shared_ptr<EdgeInfo> CreateEdgeInfo(
 
 std::shared_ptr<GraphInfo> CreateGraphInfo(
     const std::string& name, const VertexInfoVector& vertex_infos,
-    const EdgeInfoVector& edge_infos, const std::string& prefix = "",
+    const EdgeInfoVector& edge_infos, const std::string& prefix,
     std::shared_ptr<const InfoVersion> version = nullptr);
 
 const std::shared_ptr<DataType>& boolean();

cpp/src/graph_info.cc

@@ -176,6 +176,9 @@ class VertexInfo::Impl {
         property_groups_(std::move(property_groups)),
         prefix_(prefix),
         version_(std::move(version)) {
+    if (prefix_.empty()) {
+      prefix_ = label_ + "/";  // default prefix
+    }
     for (int i = 0; i < property_groups_.size(); i++) {
       const auto& pg = property_groups_[i];
       for (const auto& p : pg->GetProperties()) {
@@ -872,7 +875,9 @@ Result<std::string> EdgeInfo::Dump() const noexcept {
     node["property_groups"].PushBack();
     node["property_groups"][node["property_groups"].Size() - 1] = pg_node;
   }
-  node["version"] = impl_->version_->ToString();
+  if (impl_->version_ != nullptr) {
+    node["version"] = impl_->version_->ToString();
+  }
   std::string dump_string;
   ::Yaml::Serialize(node, dump_string);
   return dump_string;

cpp/test/test_info.cc

@@ -225,6 +225,10 @@ TEST_CASE("VertexInfo") {
     auto invalid_vertex_info2 =
         CreateVertexInfo(label, 0, {pg}, "test_vertex/", version);
     REQUIRE(invalid_vertex_info2->IsValidated() == false);
+    // check if prefix empty
+    auto vertex_info_empty_prefix =
+        CreateVertexInfo(label, chunk_size, {pg}, "", version);
+    REQUIRE(vertex_info_empty_prefix->IsValidated() == true);
   }
 
   SECTION("Dump") {
@@ -246,6 +250,9 @@ prefix: test_vertex
 version: gar/v1
 )";
     REQUIRE(dump_result.value() == expected);
+    auto vertex_info_empty_version =
+        CreateVertexInfo(label, chunk_size, {pg}, "test_vertex/");
+    REQUIRE(vertex_info_empty_version->Dump().status().ok());
   }
 
   SECTION("AddPropertyGroup") {
@@ -377,6 +384,11 @@ TEST_CASE("EdgeInfo") {
         src_label, edge_label, dst_label, chunk_size, src_chunk_size, 0,
         directed, {adj_list}, {pg}, "test_edge/", version);
     REQUIRE(invalid_edge_info6->IsValidated() == false);
+    // check if prefix empty
+    auto edge_info_with_empty_prefix = CreateEdgeInfo(
+        src_label, edge_label, dst_label, chunk_size, src_chunk_size,
+        dst_chunk_size, directed, {adj_list}, {pg}, "", version);
+    REQUIRE(edge_info_with_empty_prefix->IsValidated() == true);
   }
 
   SECTION("Dump") {
@@ -408,6 +420,10 @@ src_label: person
 version: gar/v1
 )";
     REQUIRE(dump_result.value() == expected);
+    auto edge_info_empty_version =
+        CreateEdgeInfo(src_label, edge_label, dst_label, chunk_size,
+                       src_chunk_size, dst_chunk_size, directed, {}, {});
+    REQUIRE(edge_info_empty_version->Dump().status().ok());
   }
 
   SECTION("AddAdjacentList") {
@@ -512,6 +528,10 @@ TEST_CASE("GraphInfo") {
     auto invalid_graph_info3 =
         CreateGraphInfo(name, {vertex_info}, {edge_info}, "", version);
     REQUIRE(invalid_graph_info3->IsValidated() == false);
+    // check if prefix empty, graph_info with empty prefix is invalid
+    auto graph_info_with_empty_prefix =
+        CreateGraphInfo(name, {vertex_info}, {edge_info}, "", version);
+    REQUIRE(graph_info_with_empty_prefix->IsValidated() == false);
   }
 
   SECTION("Dump") {
@@ -526,6 +546,9 @@ version: gar/v1
   - test_vertex.vertex.yaml
 )";
     REQUIRE(dump_result.value() == expected);
+    auto graph_info_empty_version =
+        CreateGraphInfo(name, {vertex_info}, {edge_info}, "test_graph/");
+    REQUIRE(graph_info_empty_version->Dump().status().ok());
   }
 
   SECTION("AddVertex") {