chore(build): allow usage of non-bundled nlohmann-json

Signed-off-by: Federico Aponte <federico.aponte@sysdig.com>

cmake/modules/falcosecurity-libs.cmake

@@ -85,6 +85,7 @@ set(BUILD_LIBSCAP_EXAMPLES OFF CACHE BOOL "")
 
 set(USE_BUNDLED_TBB ON CACHE BOOL "")
 set(USE_BUNDLED_JSONCPP ON CACHE BOOL "")
+set(USE_BUNDLED_NLOHMANN_JSON ON CACHE BOOL "")
 set(USE_BUNDLED_VALIJSON ON CACHE BOOL "")
 set(USE_BUNDLED_RE2 ON CACHE BOOL "")
 set(USE_BUNDLED_UTHASH ON CACHE BOOL "")

cmake/modules/njson.cmake

@@ -12,24 +12,10 @@
 # specific language governing permissions and limitations under the License.
 #
 
-#
-# nlohmann-json
-#
-if(NJSON_INCLUDE)
-    # Adding the custom target we can use it with `add_dependencies()`
-    if(NOT TARGET njson)
-        add_custom_target(njson)
-    endif()
-else()
-    # We always use the bundled version
-    set(NJSON_SRC "${PROJECT_BINARY_DIR}/njson-prefix/src/njson")
-    set(NJSON_INCLUDE "${NJSON_SRC}/single_include")
-    ExternalProject_Add(
-        njson
+if(USE_BUNDLED_NLOHMANN_JSON)
+    ExternalProject_Add(njson
         URL "https://github.com/nlohmann/json/archive/v3.3.0.tar.gz"
         URL_HASH "SHA256=2fd1d207b4669a7843296c41d3b6ac5b23d00dec48dba507ba051d14564aa801"
-        CONFIGURE_COMMAND ""
-        BUILD_COMMAND ""
-        INSTALL_COMMAND "")
-    message(STATUS "Using bundled nlohmann-json in '${NJSON_SRC}'")
+        CMAKE_ARGS -DCMAKE_BUILD_TYPE=Release -DJSON_BuildTests=OFF -DBUILD_TESTING=OFF
+    )
 endif()

userspace/engine/CMakeLists.txt

@@ -11,7 +11,9 @@
 # "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 # specific language governing permissions and limitations under the License.
 
-set(FALCO_ENGINE_SOURCE_FILES
+find_package(nlohmann_json CONFIG REQUIRED)
+
+add_library(falco_engine STATIC
     falco_common.cpp
     falco_engine.cpp
     falco_load_result.cpp
@@ -25,24 +27,26 @@ set(FALCO_ENGINE_SOURCE_FILES
     rule_loader.cpp
     rule_loader_reader.cpp
     rule_loader_collector.cpp
-    rule_loader_compiler.cpp)
-
-add_library(falco_engine STATIC ${FALCO_ENGINE_SOURCE_FILES})
+    rule_loader_compiler.cpp
+)
 
 if (EMSCRIPTEN)
 	target_compile_options(falco_engine PRIVATE "-sDISABLE_EXCEPTION_CATCHING=0")
 endif()
 
-add_dependencies(falco_engine yamlcpp njson)
+add_dependencies(falco_engine yamlcpp)
 
-target_include_directories(
-    falco_engine
-    PUBLIC
-      "${NJSON_INCLUDE}"
-      "${TBB_INCLUDE_DIR}"
-      "${LIBSCAP_INCLUDE_DIRS}"
-      "${LIBSINSP_INCLUDE_DIRS}"
-      "${YAMLCPP_INCLUDE_DIR}"
-      "${PROJECT_BINARY_DIR}/userspace/engine")
+target_include_directories(falco_engine
+PUBLIC
+    ${LIBSCAP_INCLUDE_DIRS}
+    ${LIBSINSP_INCLUDE_DIRS}
+    ${PROJECT_BINARY_DIR}/userspace/engine
+    ${TBB_INCLUDE_DIR}
+    ${YAMLCPP_INCLUDE_DIR}
+)
 
-target_link_libraries(falco_engine "${FALCO_SINSP_LIBRARY}" "${YAMLCPP_LIB}")
+target_link_libraries(falco_engine
+    nlohmann_json::nlohmann_json
+    ${FALCO_SINSP_LIBRARY}
+    ${YAMLCPP_LIB}
+)