Fix error resolving gazebo classic material

Signed-off-by: Ian Chen <ichen@openrobotics.org>

src/SdfEntityCreator.cc

@@ -85,6 +85,7 @@
 #include "gz/sim/components/World.hh"
 
 #include "rendering/MaterialParser/MaterialParser.hh"
+#include "ServerPrivate.hh"
 
 class gz::sim::SdfEntityCreatorPrivate
 {
@@ -808,7 +809,8 @@ Entity SdfEntityCreator::CreateEntities(const sdf::Visual *_visual)
       "https://gazebosim.org/api/sim/8/migrationsdf.html#:~:text=Materials " <<
       "for details." << std::endl;
       std::string scriptUri = visualMaterial.ScriptUri();
-      if (scriptUri != "file://media/materials/scripts/gazebo.material") {
+      if (scriptUri != ServerPrivate::kClassicMaterialScriptUri)
+      {
         gzwarn << "Custom material scripts are not supported."
           << std::endl;
       }

src/Server.cc

@@ -159,7 +159,8 @@ Server::Server(const ServerConfig &_config)
       // 'src/gui_main.cc'.
       errors = sdfRoot.Load(filePath, sdfParserConfig);
       if (errors.empty() || _config.BehaviorOnSdfErrors() !=
-          ServerConfig::SdfErrorBehavior::EXIT_IMMEDIATELY) {
+          ServerConfig::SdfErrorBehavior::EXIT_IMMEDIATELY)
+      {
         if (sdfRoot.Model() == nullptr) {
           this->dataPtr->sdfRoot = std::move(sdfRoot);
         }
@@ -197,7 +198,7 @@ Server::Server(const ServerConfig &_config)
     }
   }
 
-  if (!errors.empty())
+  if (!errors.empty()/* && !containsOnlyGazeboClassicMaterialScriptErrors(errors) */)
   {
     for (auto &err : errors)
       gzerr << err << "\n";

src/ServerPrivate.cc

@@ -37,6 +37,9 @@
 using namespace gz;
 using namespace sim;
 
+const std::string ServerPrivate::kClassicMaterialScriptUri =
+    "file://media/materials/scripts/gazebo.material";
+
 /// \brief This struct provides access to the record plugin SDF string
 struct LoggingPlugin
 {
@@ -546,6 +549,12 @@ bool ServerPrivate::ResourcePathsResolveService(
 //////////////////////////////////////////////////
 std::string ServerPrivate::FetchResource(const std::string &_uri)
 {
+  // Check if it is a gazebo classic material URI
+  // Return original URI string. The MaterialParser will handle this URI.
+  if (_uri == kClassicMaterialScriptUri)
+    return _uri;
+
+  // Fetch resource from fuel
   auto path =
       fuel_tools::fetchResourceWithClient(_uri, *this->fuelClient.get());
 

src/ServerPrivate.hh

@@ -187,6 +187,11 @@ namespace gz
       /// Server. It is used in the SDFormat world generator when saving worlds
       public: std::unordered_map<std::string, std::string> fuelUriMap;
 
+      /// \brief Gazebo classic material URI string
+      /// Only gazebo classic material script uri matching this still will be
+      /// migrated to gz.
+      public: static const std::string kClassicMaterialScriptUri;
+
       /// \brief List of names for all worlds loaded in this server.
       private: std::vector<std::string> worldNames;
 

test/integration/material.cc

@@ -296,3 +296,30 @@ TEST_F(MaterialTest, InvalidColor)
   EXPECT_EQ(math::Color(0.0f, 0.0f, 0.0f, 1.0f),
             boxVisualComp->Data().Specular());
 }
+
+TEST_F(MaterialTest, WorldWithClassicMaterial)
+{
+  ServerConfig serverConfig;
+  serverConfig.SetSdfFile(common::joinPaths(PROJECT_SOURCE_PATH,
+      "test/worlds/classic_material.sdf"));
+
+  std::cout << "Loading: " << serverConfig.SdfFile() << std::endl;
+  this->StartServer(serverConfig);
+
+  auto model = this->GetModel("box");
+  ASSERT_TRUE(model.Valid(*this->ecm));
+
+  auto boxVisualEntity =
+    this->ecm->EntityByComponents(components::Name("box_visual"));
+  ASSERT_NE(kNullEntity, boxVisualEntity);
+
+  // Blue color
+  auto boxVisualComp =
+    this->ecm->Component<components::Material>(boxVisualEntity);
+  EXPECT_EQ(math::Color(0.0f, 0.0f, 1.0f, 1.0f),
+            boxVisualComp->Data().Ambient());
+  EXPECT_EQ(math::Color(0.0f, 0.0f, 1.0f, 1.0f),
+            boxVisualComp->Data().Diffuse());
+  EXPECT_EQ(math::Color(0.1f, 0.1f, 0.1f, 1.0f),
+            boxVisualComp->Data().Specular());
+}