On Thu, Feb 26, 2015 at 11:55 PM, Kevin Baker <[email protected]> wrote:

> Hi,
>
> Thanks for all your work with protobuf. I am excited about the changes
> with proto3 that will reduce errors (no forgetting to set has_* in nanopb,
> yay!) and will make mapping into new languages much simpler, helping our
> interop case a lot.
>
> My question is: We are currently using protobuf pretty extensively and it
> looks like we will not be impacted by any changes in proto3 in our proto
> files (all fields being present, removal of required, default values, etc.)
> Does this mean our existing proto2 applications are compatible on-the-wire
> with proto3?
>
Yes.


> How upwards-compatible is proto3 with proto2?
>
Proto3 uses the same wire-format as proto2. A proto2 application should be
able to parse the output of a proto3 server using the same .proto
definition (only differing in syntax version). It's also true vice versa.


>
> Of course I will test this as well but I was wondering if there are any
> planned breakages of the wire format or if they will be compatibly phased
> in.
>
There is no planned wire-format changes for proto3.


>
> Thanks,
> Kevin
>
> On Sunday, February 8, 2015 at 10:04:30 PM UTC-6, Feng Xiao wrote:
>>
>>
>>
>> On Sat, Feb 7, 2015 at 4:31 AM, Jeremy Swigart <[email protected]> wrote:
>>
>>> I don't understand. If a message is a simple struct then the generated
>>> wrapper code would populate it with the default as defined by the proto it
>>> was compiled with wouldn't it? Are you suggesting that the implementation
>>> on different platforms would lack the wrapper objects generated by protobuf?
>>
>> There may be languages whose protobuf implementation would not be able to
>> efficiently support these features. Note that these decisions are not made
>> based on the current languages that we support, but based on that we are
>> going to support a much wider range of languages.
>>
>>
>>> As long as you have that you have the default value. This rationale
>>> doesn't make sense.
>>>
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>>
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