Problem
I've been developing a game in C++ in my spare time and I've opted to use Bazel as my build tool since I have never had a ton of luck (or fun) working with make or cmake. I also have dependencies in other languages (python for some of the high level scripting). I'm using glfw for basic window handling and high level graphics support and that works well enough but now comes the problem. I'm uncertain on how I should handle dependencies like glfw in a Bazel world.
For some of my dependencies (like gtest and fruit) I can just reference them in my WORKSPACE file and Bazel handles them automagically but glfw hasn't adopted Bazel. So all of this leads me to ask, what should I do about dependencies that don't use Bazel inside a Bazel project?
Current approach
For many of the simpler dependencies I have, I simply created a new_git_repository entry in my WORKSPACE file and created a BUILD file for the library. This works great until you get to really complicated libraries like glfw that have a number of dependencies on their own.
When building glfw for a Linux machine running X11 you now have a dependency on X11 which would mean adding X11 to my Bazel setup. X11 Comes with its own set of dependencies (the X11 libraries like X11Cursor) and so on.
glfw also tries to provide basic joystick support which is provided by default in Linux which is great! Except that this is provided by the kernel which means that the kernel is also a dependency of my project. Now I shouldn't need anything more than the kernel headers this still seems like a lot to bring in.
Alternative Options
The reason I took the approach I've taken so far is to make the dependencies required to spin up a machine that can successfully build my game very minimal. In theory they just need a C/C++ compiler, Java 8, and Bazel and they're off to the races. This is great since it also means I can create a Docker container that has Bazel installed and do CI/CD really easily.
I could sacrifice this ease and just say that you need to have libraries like glfw installed before attempting to compile the game but that brings the whole which version is installed and how is it all configured problem back up that Bazel is supposed to help solve.
Surely there is a simpler solution and I'm overthinking this?
If the glfw project has no BUILD files, then you have the following options:
Build glfw inside a genrule.
If glfw supports some other build system like make, you could create a genrule that runs the tool. This approach has obvious drawbacks, like the not-to-be-underestimated impracticality of having to declare all inputs of that genrule, but it'd be the simplest way of Bazel'izing glfw.
Pre-build glfw.o and check it into your source tree.
You can create a cc_library rule for it, and put the .o file in the srcs. Even though this solution is the least flexible of all because you not only restrict the target platform to whatever the .o was built for, but also make it harder to reproduce the whole build, the benefits are sometimes worth the costs.
I view this approach as a last resort. Even in Bazel's own source code there's one cc_library.srcs that includes a raw object file, because it was worth it, as the commit message of 92caf38 explains.
Require that glfw be installed.
You already considered this option. Some people may prefer this to the other approaches.