How to include private header files of other Modules into my Module?

[anonymous_user_ac78c893]

I’ve tried to do that in many ways without success, but finally nailed it!

This works for engine modules:

using System.IO; // Note this import, it's needed below

namespace UnrealBuildTool.Rules
{
    public class Foo : ModuleRules
    {
        public Foo(TargetInfo Target)
        {
            // ...
            // Get the engine path. Ends with "Engine/"
            string engine_path = Path.GetFullPath(BuildConfiguration.RelativeEnginePath);
            // Now get the base of UE4's modules dir (could also be Developer, Editor, ThirdParty)
            string srcrt_path = engine_path + "Source/Runtime/";
    
            // now you can include the module's private paths!
            // as an example, you can expose UE4's abstraction of D3D11, located in Source/Runtime/Windows/D3D11RHI
            PublicIncludePaths.Add(srcrt_path + "Windows/D3D11RHI/Private");
            PublicIncludePaths.Add(srcrt_path + "Windows/D3D11RHI/Private/Windows");
        }
    }
}