@spec merge(struct() | nil, struct() | nil) :: struct() | nil

Singular fields of msg will be overwritten, if specified in from, except for embedded messages which will be merged. Repeated fields will be concatenated.

Note that "specified" has a different meaning in protobuf 2 and 3:

• 2: if the singular field from from is nil, the value from msg is kept

• 3: if the singular field from from is set to the default value, the value from msg is kept. This behaviour matches the C++ reference implementation behaviour.

• msg and from must be of the same type; or

• either msg or from is nil: the non-nil message is returned; or

• both are nil: nil is returned

Example

iex> r1 = %Protobuf2Message{a: 0, b: :ONE}
iex> r2 = %Protobuf2Message{a: nil, b: :TWO}
iex> Protox.MergeMessage.merge(r1, r2)
%Protobuf2Message{a: 0, b: :TWO}
iex> Protox.MergeMessage.merge(r2, r1)
%Protobuf2Message{a: 0, b: :ONE}