#2 Conan package support

[uilianries]

Hi!

This PR is related to issue #2

Here I added the complete Conan recipe to build BehaviorTreeCPP. The recipe has some attributes, including options (shared and zmq support) and some functions to build your project.

Conan provides an excellent CMake integration. As you can see, both examples and tests are disabled when creating the package. Also, there is a little patch on line 41 where Conan is included in your cmake file. The patch is needed to solve ZMQ and cmake definitions, as BUILD_SHARED_LIBS when the option shared is True.

To build this project using Conan:

$ pip install conan
$ cd BehaviorTree.CPP/
$ conan create . BehaviorTree.CPP/<version>@BehaviorTree/stable

The command conan create will copy all files listed by exports_sources to build directory and will execute all cmake steps, including configure, build and install. The requirement ZMQ C++ will be resolved by Conan automatically. There is the option zmq to exclude it as a dependency when requested. By default, will produce BehaviorTree.CPP as static library and linking cppzmq. Your project folder will not be changed by Conan after to build.

To build BehaviorTree.CPP as shared library and standalone (without zmq):

$ conan create . BehaviorTree.CPP/<version>@BehaviorTree/stable -o BehaviorTree.CPP:shared=True -o BehaviorTree.CPP:zmq=False

The package reference BehaviorTree.CPP/<version>@BehaviorTree/stable is just a suggestion. You can rename as you prefer.

This PR is the first one of two. After to accept (or not) this PR, I'll create a new one to introduce Conan in your CI (travis and appveyor) to distribute BehaviorTree.CPP as Conan package (recipe and pre-built packages) on Bintray

Adding Conan experts to review this PR together:
/cc @memsharded @danimtb @SSE4

closes #2

Regards!

[memsharded]

For the 3rdparty, it would be nice to be able to avoid it and use conan packages.
I think there are packages for flatbuffers and for tinyXML2.

This could be done later too, not critical, though it might save some building time too, and avoid conflicts for users using those libraries too.

[facontidavide]

Indeed. If you notice: https://github.com/BehaviorTree/BehaviorTree.CPP/blob/master/CMakeLists.txt#L30

When ZMQ is detected the definition ZMQ_FOUND is added, otherwise, it isn't.

[uilianries]

both flatbuffers and tinyXML2 cpp files are compiled directly with BehaviorTree. We could change the cmake file to use both cpp files from Conan but could result in different ABI when building with/without Conan.

[facontidavide]

FYI:

tinyXML2, minitracer and ZMQ are all is "hidden" both in terms of API and ABI.
I removed any reference to these libraries in the header files and I used the Pimpl idiom.

There is a single class, PublisherZMQ, whihc requires ZMQ.
A possible solution might be to release BehaviorTree.CPP without ZMQ and PublisherZMQ as a separate projects.

[memsharded]

Shouldn't this have some effect on the build? Like some option USE_ZMQ to CMakeLists?

[uilianries]

well, find_package for ZMQ is not mandatory so we could build BehaviorTree without cppzmq. I think it could be an option for tiny version of package.

[facontidavide]

I will try to review and merge this tomorrow

[facontidavide]

I finally decided to make ZMQ not an optional but a mandatory requirement.
Since conan makes dependencies easier, I think it makes sense ;)

I slightly modifed your file and included it. Thanks

[uilianries]

Thanks!

I'll open a new PR including CI support. BehaviorTree could be built by Conan and distributed on Conan Center