lava commented on a change in pull request #326: MESOS-6874: Validate the match
between Type and *Infos in the ContainerInfo.
URL: https://github.com/apache/mesos/pull/326#discussion_r265964585
##########
File path: src/common/protobuf_utils.hpp
##########
@@ -64,6 +64,63 @@ struct Slave;
namespace protobuf {
+//
+// A "protobuf union" is a protobuf message
+// which has an enum named "Type" defined in its scope,
+// a required field named "type" of a "Type" type
+// and a field corresponding to each member of the "Type" enum.
+//
+// A valid "protobuf union" should satisfy the following requirements.
+// 1. A member of the Type enum with a number (not index!) of 0,
+// if there is any, should be named "UNKNOWN".
+// 2. For each other member of the Type enum there should be an optional field
+// in the message with an exactly matching name in lowercase.
+// 3. The fields that correspond to members of the Type enum other than
+// message.type(), should not be set.
+//
+// NOTE: If possible, oneof should be used in the new messages instead
+// of the "protobuf union".
+//
+class UnionValidatorHelper
+{
+public:
+ UnionValidatorHelper(
+ const google::protobuf::Descriptor*,
+ const google::protobuf::EnumDescriptor*);
+
+ Option<Error> Validate(
+ const int messageTypeNumber, const google::protobuf::Message&) const;
+
+private:
+ std::vector<std::pair<int, const google::protobuf::FieldDescriptor*>>
+ UnionFieldDescriptors;
+ const google::protobuf::EnumDescriptor* TypeDescriptor;
+};
+
+
+template <class Message>
+class UnionValidator
+{
+public:
+ static Option<Error> Validate(const Message& message)
+ {
+ static const UnionValidatorHelper helper(
+ Message::descriptor(), Message::Type_descriptor());
+ return helper.Validate(message.type(), message);
+ };
+ UnionValidator() = delete;
+};
+
+
+// This function returns Error if the protobuf union is not valid
+// and Nothing otherwise.
Review comment:
Let's also mention that it will abort the process if the passed message is
not a protobuf union. (which is actually the correct behaviour, I think,
because getting the wrong message type here is essentially a compile-time bug
that is only detected at runtime)
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