AP_Scripting: add arming check for failed scripts

libraries/AP_Scripting/AP_Scripting.cpp

@@ -154,9 +154,8 @@ void AP_Scripting::init(void) {
 
     if (!hal.scheduler->thread_create(FUNCTOR_BIND_MEMBER(&AP_Scripting::thread, void),
                                       "Scripting", SCRIPTING_STACK_SIZE, AP_HAL::Scheduler::PRIORITY_SCRIPTING, 0)) {
-        gcs().send_text(MAV_SEVERITY_CRITICAL, "Could not create scripting stack (%d)", SCRIPTING_STACK_SIZE);
-        gcs().send_text(MAV_SEVERITY_ERROR, "Scripting failed to start");
-        _init_failed = true;
+        gcs().send_text(MAV_SEVERITY_ERROR, "Scripting: %s", "failed to start");
+        _thread_failed = true;
     }
 }
 
@@ -222,6 +221,7 @@ void AP_Scripting::thread(void) {
         // reset flags
         _stop = false;
         _restart = false;
+        _init_failed = false;
 
         lua_scripts *lua = new lua_scripts(_script_vm_exec_count, _script_heap_size, _debug_options, terminal);
         if (lua == nullptr || !lua->heap_allocated()) {
@@ -281,6 +281,31 @@ void AP_Scripting::handle_mission_command(const AP_Mission::Mission_Command& cmd
     mission_data->push(cmd);
 }
 
+bool AP_Scripting::arming_checks(size_t buflen, char *buffer) const
+{
+    if (!enabled()) {
+        return true;
+    }
+
+    if (_thread_failed) {
+        hal.util->snprintf(buffer, buflen, "Scripting: %s", "failed to start");
+        return false;
+    }
+
+    if (_init_failed) {
+        hal.util->snprintf(buffer, buflen, "Scripting: %s", "out of memory");
+        return false;
+    }
+
+    const char *error_buf = lua_scripts::get_last_error_message();
+    if (error_buf != nullptr) {
+        hal.util->snprintf(buffer, buflen, "Scripting: %s", error_buf);
+        return false;
+    }
+
+    return true;
+}
+
 AP_Scripting *AP_Scripting::_singleton = nullptr;
 
 namespace AP {

libraries/AP_Scripting/AP_Scripting.h

@@ -38,7 +38,6 @@ public:
     AP_Scripting &operator=(const AP_Scripting&) = delete;
 
     void init(void);
-    bool init_failed(void) const { return _init_failed; }
 
     bool enabled(void) const { return _enable != 0; };
     bool should_run(void) const { return enabled() && !_stop; }
@@ -51,6 +50,8 @@ public:
 
     void handle_mission_command(const class AP_Mission::Mission_Command& cmd);
 
+    bool arming_checks(size_t buflen, char *buffer) const;
+
    // User parameters for inputs into scripts 
    AP_Float _user[6];
 
@@ -102,6 +103,7 @@ private:
     AP_Int8 _debug_options;
     AP_Int16 _dir_disable;
 
+    bool _thread_failed; // thread allocation failed
     bool _init_failed;  // true if memory allocation failed
     bool _restart; // true if scripts should be restarted
     bool _stop; // true if scripts should be stopped

libraries/AP_Scripting/lua_scripts.cpp

@@ -531,12 +531,9 @@ void lua_scripts::run(void) {
         // re-print the latest error message every 10 seconds 10 times
         const uint8_t error_prints = 10;
         if ((print_error_count < error_prints) && (AP_HAL::millis() - last_print_ms > 10000)) {
+            // note that we do not clear the buffer after we have finished printing, this allows it to be used for a pre-arm check
             print_error(MAV_SEVERITY_DEBUG);
             print_error_count++;
-            if ((print_error_count >= error_prints) && (error_msg_buf != nullptr)) {
-                hal.util->heap_realloc(_heap, error_msg_buf, 0);
-                error_msg_buf = nullptr;
-            }
         }
     }
 

libraries/AP_Scripting/lua_scripts.h

@@ -141,4 +141,7 @@ public:
     // must be static for use in atpanic, public to allow bindings to issue none fatal warnings
     static void set_and_print_new_error_message(MAV_SEVERITY severity, const char *fmt, ...) FMT_PRINTF(2,3);
 
+    // return last error message, nullptr if none
+    static const char* get_last_error_message() { return error_msg_buf; }
+
 };