on_deactivate: distinguish removal and unloading (minetest#11931)

Sometimes you need to be able to do removal-related cleanup, such as removing files from disk, or entries from a database. staticdata obviously isn't suitable for large data. The data shouldn't be removed if the entity is unloaded, only if it is removed.

doc/lua_api.txt

@@ -4551,8 +4551,14 @@ Callbacks:
  * Called when the object is instantiated.
  * `dtime_s` is the time passed since the object was unloaded, which can be
  used for updating the entity state.
-* `on_deactivate(self)
+* `on_deactivate(self, removal)
  * Called when the object is about to get removed or unloaded.
+ * `removal`: boolean indicating whether the object is about to get removed.
+ Calling `object:remove()` on an active object will call this with `removal=true`.
+ The mapblock the entity resides in being unloaded will call this with `removal=false`.
+ * Note that this won't be called if the object hasn't been activated in the first place.
+ In particular, `minetest.clear_objects({mode = "full"})` won't call this,
+ whereas `minetest.clear_objects({mode = "quick"})` might call this.
 * `on_step(self, dtime)`
  * Called on every server tick, after movement and collision processing.
  `dtime` is usually 0.1 seconds, as per the `dedicated_server_step` setting

games/devtest/mods/testentities/callbacks.lua

@@ -31,8 +31,8 @@ minetest.register_entity("testentities:callback", {
  on_activate = function(self, staticdata, dtime_s)
  message("Callback entity: on_activate! pos="..spos(self).."; dtime_s="..dtime_s)
  end,
- on_deactivate = function(self)
- message("Callback entity: on_deactivate! pos="..spos(self))
+ on_deactivate = function(self, removal)
+ message("Callback entity: on_deactivate! pos="..spos(self) .. "; removal=" .. tostring(removal))
  end,
  on_punch = function(self, puncher, time_from_last_punch, tool_capabilities, dir, damage)
  local name = get_object_name(puncher)

src/script/cpp_api/s_entity.cpp

@@ -103,7 +103,7 @@ void ScriptApiEntity::luaentity_Activate(u16 id,
  lua_pop(L, 2); // Pop object and error handler
 }
 
-void ScriptApiEntity::luaentity_Deactivate(u16 id)
+void ScriptApiEntity::luaentity_Deactivate(u16 id, bool removal)
 {
  SCRIPTAPI_PRECHECKHEADER
 
@@ -120,9 +120,9 @@ void ScriptApiEntity::luaentity_Deactivate(u16 id)
  if (!lua_isnil(L, -1)) {
  luaL_checktype(L, -1, LUA_TFUNCTION);
  lua_pushvalue(L, object);
-
+ lua_pushboolean(L, removal);
  setOriginFromTable(object);
- PCALL_RES(lua_pcall(L, 1, 0, error_handler));
+ PCALL_RES(lua_pcall(L, 2, 0, error_handler));
  } else {
  lua_pop(L, 1);
  }

src/script/cpp_api/s_entity.h

@@ -33,7 +33,7 @@ class ScriptApiEntity
  bool luaentity_Add(u16 id, const char *name);
  void luaentity_Activate(u16 id,
  const std::string &staticdata, u32 dtime_s);
- void luaentity_Deactivate(u16 id);
+ void luaentity_Deactivate(u16 id, bool removal);
  void luaentity_Remove(u16 id);
  std::string luaentity_GetStaticdata(u16 id);
  void luaentity_GetProperties(u16 id,

src/server/luaentity_sao.cpp

@@ -117,13 +117,13 @@ void LuaEntitySAO::addedToEnvironment(u32 dtime_s)
  }
 }
 
-void LuaEntitySAO::dispatchScriptDeactivate()
+void LuaEntitySAO::dispatchScriptDeactivate(bool removal)
 {
  // Ensure that this is in fact a registered entity,
  // and that it isn't already gone.
  // The latter also prevents this from ever being called twice.
  if (m_registered && !isGone())
- m_env->getScriptIface()->luaentity_Deactivate(m_id);
+ m_env->getScriptIface()->luaentity_Deactivate(m_id, removal);
 }
 
 void LuaEntitySAO::step(float dtime, bool send_recommended)

src/server/luaentity_sao.h

@@ -80,9 +80,9 @@ class LuaEntitySAO : public UnitSAO
  bool collideWithObjects() const;
 
 protected:
- void dispatchScriptDeactivate();
- virtual void onMarkedForDeactivation() { dispatchScriptDeactivate(); }
- virtual void onMarkedForRemoval() { dispatchScriptDeactivate(); }
+ void dispatchScriptDeactivate(bool removal);
+ virtual void onMarkedForDeactivation() { dispatchScriptDeactivate(false); }
+ virtual void onMarkedForRemoval() { dispatchScriptDeactivate(true); }
 
 private:
  std::string getPropertyPacket();