kaysoky 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_r266586290
##########
File path: src/common/protobuf_utils.hpp
##########
@@ -64,6 +64,53 @@ 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 UnionValidator
+{
+public:
+ UnionValidator(
+ 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_;
+};
+
+
+// This function returns Error if the protobuf union is not valid
+// and Nothing otherwise.
+// In case MessageWithUnion is not a protobuf union,
+// this function will abort the process on the first use.
+template <class MessageWithUnion>
+Option<Error> validateProtobufUnion(const MessageWithUnion& message)
+{
+ static const UnionValidator validator(
+ MessageWithUnion::descriptor(), MessageWithUnion::Type_descriptor());
Review comment:
Looking at this again, arriving at a `google::protobuf::EnumDescriptor` for
the second argument can be easily missed, especially for those unfamiliar with
protobuf generated code. A note like this might help:
```
// NOTE: The `::Type_descriptor()` method is a protobuf generated method
corresponding
// to the `Type` field of the given protobuf. We expect this to be an enum
field.
```
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