Null String in C# (CheckForNull)

[Everton Araujo]

Hi all,

I'm facing the situation where a string value is not allowed to be null in Protobuf 3 using C# (CheckNotNull).

I do not understand it considering that fields are optional by default in proto3.

Does anyone knows the original reason for this constraint? As far as I could see, it happens for string and bytearrays.

Regards,

Everton

[Marc Gravell]

Fields are optional but the implicit default for a string is a zero length string, not a null length string. To be honest, either approach seems perfectly reasonable as long as it is documented and any exception is clear and obvious. For my separate implementation I chose to interpret nulls as "meh, not set, ignore it", but... either is fine IMO.

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Regards,

Marc

[Jon Skeet]

Exactly. In an early implementation I treated null and empty string as the same - but it ends up being weird in all kinds of ways. (Either setting a property and then fetching it isn't a roundtrip, or serializing and deserializing isn't a roundtrip.)

In the end, I went with "stick to protobuf semantics: every string has a value, which is empty by default."

If you use the StringValue wrapper type, you then can use null, which means "there's no StringValue here".

On Tuesday, 3 October 2017 22:06:26 UTC+1, Marc Gravell wrote:

Fields are optional but the implicit default for a string is a zero length string, not a null length string. To be honest, either approach seems perfectly reasonable as long as it is documented and any exception is clear and obvious. For my separate implementation I chose to interpret nulls as "meh, not set, ignore it", but... either is fine IMO.

On 3 October 2017 at 19:35, Everton Araujo <everto...@gmail.com> wrote:

Hi all,

I'm facing the situation where a string value is not allowed to be null in Protobuf 3 using C# (CheckNotNull).

I do not understand it considering that fields are optional by default in proto3.

Does anyone knows the original reason for this constraint? As far as I could see, it happens for string and bytearrays.

Regards,

Everton

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Regards,

Marc