leave out an optional field in the message, but not a required field, regardless of the default value passed along.</p>
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<p>Personally I have not yet seen compelling reasons for not favoring optional values. Again, say, unexpectedly, some writer cannot provide some required field, but it turns out that the message would still be useful. If you had worked with optional fields, there was no problem, but now you will have to provide some meaningless value to make the encoding succ