Throw if metadata file's root is not a YAML map

Fixes #681.

CMakeLists.txt

@@ -101,7 +101,7 @@ set(PSEUDOSEM_INCLUDE_DIRS "${SOURCE_DIR}/include")
 
 ExternalProject_Add(testing-metadata
                     PREFIX "external"
-                    URL "https://github.com/loot/testing-metadata/archive/1.1.0.tar.gz"
+                    URL "https://github.com/loot/testing-metadata/archive/1.2.0.tar.gz"
                     CONFIGURE_COMMAND ""
                     BUILD_COMMAND ""
                     INSTALL_COMMAND "")

src/backend/metadata_list.cpp

@@ -44,13 +44,16 @@ void MetadataList::Load(const boost::filesystem::path& filepath) {
   YAML::Node metadataList = YAML::Load(in);
   in.close();
 
+  if (!metadataList.IsMap())
+    throw FileAccessError("The root of the metadata file " + filepath.string() + " is not a YAML map.");
+
   if (metadataList["plugins"]) {
     for (const auto& node : metadataList["plugins"]) {
       PluginMetadata plugin(node.as<PluginMetadata>());
       if (plugin.IsRegexPlugin())
         regexPlugins_.push_back(plugin);
       else if (!plugins_.insert(plugin).second)
-          throw FileAccessError("More than one entry exists for \"" + plugin.Name() + "\"");
+        throw FileAccessError("More than one entry exists for \"" + plugin.Name() + "\"");
     }
   }
   if (metadataList["globals"])

src/tests/backend/metadata_list_test.h

@@ -37,7 +37,9 @@ protected:
     metadataPath("./testing-metadata/masterlist.yaml"),
     savedMetadataPath("./testing-metadata/saved.masterlist.yaml"),
     missingMetadataPath("./missing-metadata.yaml"),
-    invalidMetadataPaths({"./testing-metadata/invalid/non_unique.yaml"}) {}
+    invalidMetadataPaths({
+      "./testing-metadata/invalid/non_map_root.yaml",
+      "./testing-metadata/invalid/non_unique.yaml"}) {}
 
   inline virtual void SetUp() {
     CommonGameTestFixture::SetUp();