Add Protocolor Buffers 3

[Osse]

No description provided.

[ruslo]

Testing:

• https://travis-ci.org/ingenue/hunter/builds/151415877

[ruslo]

Testing

Failed. @Osse please investigate.

[Osse]

To make use of the convenience macros, such as protobuf_generate_cpp which is the cause of the errors here, you have to set(protobuf_MODULE_COMPATIBLE TRUE). It works if you set it before find_package(Protobuf).

I don't know if it can be made part of the Hunter package configuration somehow. I suspect it can't since the file will be read when configuring the main project. Alternatively we can remove the if() as part of the hunterization, but that breaks more with upstream. I asked about what the intention of this guard is, but I didn't get a clear answer. It can also be documented in the Wiki, but I decided to not update it until the PR was accepted, but I can update it immediately if you wish.

[ruslo]

I don't know details but Protobuf example has worked before: https://travis-ci.org/ingenue/hunter/builds/121754452 and now it stops. You will break old code with this update, that's my point :) At first glance this looks like a bug somewhere, either in upstream or in hunterization.

To make use of the convenience macros, such as protobuf_generate_cpp which is the cause of the errors here,

Example is not using such module

[Osse]

I agree this will break old code if nothing is changed, which is bad. However, I thought it would break old code anyway, because of the change of the namespace name (Protobuf::to protobuf::).

Example is not using such module

Yes it does. This function is no longer provided by protobuf-config.cmake unless the variable I mentioned above is set which leads to the error in Jenkins This is a change in the upstream CMake files between beta2 and the relase of v3.0.0.

[ruslo]

Yes it does.

Indeed, sorry missed that.

This is a change in the upstream CMake files between beta2 and the relase of v3.0.0

Okay I see. What is the way to use this code without set(protobuf_MODULE_COMPATIBLE TRUE)? You can add one example Protobuf-compat with this variable and new example for Protobuf. We can test both.

[ruslo]

Implemented here: #496