Better error message and avoiding enum forward declarations.

emitters/yaml_base_emitter.cpp

@@ -339,14 +339,20 @@ bool yaml_base_emitter::check_object_array(const std::string& filepath,
         check_notify(filepath, nodepath, key, validate_message, update_message);
     };
 
+    const auto notify_fail = [&](const std::string& message) {
+        check_notify(filepath, nodepath, key, message, message);
+    };
+
     if (!expected_node.count(key)) {
-        throw std::runtime_error("missing expected array?");
+        notify_fail("missing expected array");
+        throw std::runtime_error("Merge object array failure");
     }
 
     const json& expected = expected_node[key];
 
     if (!expected.is_array()) {
-        throw std::runtime_error("expected type mismatch?");
+        notify_fail("expected type mismatch");
+        throw std::runtime_error("Merge object array failure");
     }
 
     json& result = merged_node[key];

emitters/yaml_enum_emitter.cpp

@@ -45,6 +45,9 @@ bool yaml_enum_emitter::do_merge(const std::string& filepath,
 bool yaml_enum_emitter::emit(const json& j) {
     const std::string& name = j["name"];
 
+    // Most likely an enum forward declaration. Nothing to document here.
+    if (j["values"].empty()) return true;
+
     std::string filename;
     for (const auto& ns : j["namespaces"]) {
         filename += static_cast<const std::string&>(ns) + "::";