Detect if the user wants Julia bindings and fail if Julia is not found.

CMakeLists.txt

@@ -26,6 +26,14 @@ else ()
   option(BUILD_SHARED_LIBS
       "Compile shared libraries (if OFF, static libraries are compiled)." ON)
 endif()
+
+# Detect whether the user passed BUILD_JULIA_BINDINGS in order to determine if
+# we should fail if Julia isn't found.
+if (BUILD_JULIA_BINDINGS)
+  set(FORCE_BUILD_JULIA_BINDINGS ON)
+else()
+  set(FORCE_BUILD_JULIA_BINDINGS OFF)
+endif()
 option(BUILD_JULIA_BINDINGS "Build Julia bindings." ON)
 
 # Build Markdown bindings for documentation.  This is used as part of website

src/mlpack/bindings/julia/CMakeLists.txt

@@ -2,7 +2,12 @@ if (BUILD_JULIA_BINDINGS)
   ## We need to check here if Julia is even available.  Although actually
   ## technically, I'm not sure if we even need to know!  For the tests though we
   ## do.  So it's probably a good idea to check.
-  find_package(Julia 0.7.0)
+  if (FORCE_BUILD_JULIA_BINDINGS)
+    find_package(Julia 0.7.0 REQUIRED)
+  else ()
+    find_package(Julia 0.7.0)
+  endif ()
+
   if (NOT JULIA_FOUND)
     # We can't build anything, so define the macro to do nothing.
     macro (add_julia_binding name)