Question: Is there any way to know when a schema will have a fixed size and what size it will be? about bond HOT 4 CLOSED

This can only be answered for a pair (schema, protocol). For example in Compact Binary almost all types are variable length, the only exceptions are bool, float and double and 8-bit integers. In Fast Binary all integer are fixed size. Furthermore most protocols omit optional fields that are set to default value.

There is no such API.

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Can be done from outside of Bond internals? (If there is no such API).
Is there any intention to provide such an API?
If possible how?

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The rules for determining if a schema is const length for a given protocol would have to hardcoded per protocol. There is no way to determine it programmatically. One could in theory imagine some way to encoding this as protocol metadata but I think it would only make sense to add if Bond itself had some feature taking advantage of fixed size fields.

As for determining what the size of a fixed length schema is, the easiest way would be to serialize an instance (e.g. default instance) to a stream that just counts bytes. We have a stream like that implemented in C++ and use it to calculate lengths in the first pass of Compact Binary v2 serialization.

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Yes, I was actually thinking into implementing our own SimpleFastProtocol disallowing variable size types altogether; where we can estimate that without much problems. The solution used in C++ would also work, we use counting streams ourselves too.

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