Make nlohmann_json optional

CMakeLists.txt

@@ -591,7 +591,13 @@ if(HAVE_LIBPCRE AND HAVE_PCRE_H)
   set(ZM_PCRE 1)
 endif()
 
-find_package(nlohmann_json)
+find_package(nlohmann_json CONFIG)
+if(nlohmann_json_FOUND)
+  set(ZM_HAS_NLOHMANN_JSON 1)
+else()
+  set(ZM_HAS_NLOHMANN_JSON 0)
+  message(AUTHOR_WARNING "nlohmann_json headers weren't found - AI results will not be available")
+endif()
 
 # Check for mmap and enable in all components
 set(ZM_MEM_MAPPED 0)

src/zm_packet.h

@@ -29,7 +29,9 @@
 #include <mutex>
 #include <vector>
 
+#if HAS_NLOHMANN_JSON
 #include <nlohmann/json.hpp>
+#endif
 
 extern "C" {
 #include <libavformat/avformat.h>
@@ -61,7 +63,9 @@ class ZMPacket {
   bool decoded;
   std::vector<ZoneStats> zone_stats;
   std::string  alarm_cause;
+#if HAS_NLOHMANN_JSON
   nlohmann::json detections;
+#endif
 
  public:
   AVPacket *av_packet() { return packet.get(); }

zoneminder-config.cmake

@@ -47,6 +47,7 @@
 /* Few ZM options that are needed by the source code */
 #cmakedefine ZM_MEM_MAPPED 1
 #cmakedefine ZM_HAS_V4L2 1
+#cmakedefine ZM_HAS_NLOHMANN_JSON 1
 
 /* Its safe to assume that signal return type is void. This is a fix for zm_signal.h */
 #define RETSIGTYPE void