Add tr_ledge obsoletion

data/json/obsoletion_and_migration_0.I/obsolete_traps.json

@@ -0,0 +1,7 @@
+[
+  {
+    "type": "trap_migration",
+    "from_ter": "tr_ledge",
+    "to_ter": "tr_null"
+  }
+]

doc/OBSOLETION_AND_MIGRATION.md

@@ -164,15 +164,49 @@ Move multiple ids that don't need to be unique any more to a single id
   }
 ```
 
+# Trap migration
+
+Trap migration replaces the provided id as submaps are loaded. You can use `tr_null` with `to_trap` to remove the trap entirely without creating errors.
+
+```json
+{
+    "type": "trap_migration",   // Mandatory. String. Must be "trap_migration"
+    "from_trap": "tr_old_trap",        // Mandatory. String. Id of the trap to replace.
+    "to_trap": "tr_new_trap",      // Mandatory. String. Id of the new trap to place.
+},
+```
+
+## Examples
+
+Migrate an id
+
+```json
+  {
+    "type": "trap_migration",
+    "from_trap": "tr_being_migrated_id",
+    "to_trap": "tr_new_id"
+  }
+```
+
+Errorlessly obsolete an id
+
+```json
+  {
+    "type": "trap_migration",
+    "from_trap": "tr_being_obsoleted_id",
+    "to_trap": "tr_null"
+  }
+```
+
 # Field migration
 
 Field migration replaces the provided id as submaps are loaded. You can use `fd_null` with `to_field` to remove the field entirely without creating errors.
 
 ```json
 {
     "type": "field_type_migration",   // Mandatory. String. Must be "field_type_migration"
-    "from_field": "t_old_field",        // Mandatory. String. Id of the field to replace.
-    "to_field": "f_new_field",      // Mandatory. String. Id of the new field to place.
+    "from_field": "fd_old_field",        // Mandatory. String. Id of the field to replace.
+    "to_field": "fd_new_field",      // Mandatory. String. Id of the new field to place.
 },
 ```
 

src/init.cpp

@@ -345,6 +345,7 @@ void DynamicDataLoader::initialize()
         requirement_data::load_requirement( jo, string_id<requirement_data>::NULL_ID(), true );
     } );
     add( "trap", &trap::load_trap );
+    add( "trap_migration", &trap_migrations::load );
 
     add( "AMMO", []( const JsonObject & jo, const std::string & src ) {
         item_controller->load_ammo( jo, src );
@@ -748,6 +749,7 @@ void DynamicDataLoader::unload_data()
     ter_furn_migrations::reset();
     ter_furn_transform::reset();
     trap::reset();
+    trap_migrations::reset();
     unload_talk_topics();
     VehicleGroup::reset();
     VehiclePlacement::reset();
@@ -935,6 +937,7 @@ void DynamicDataLoader::check_consistency()
             { _( "Start locations" ), &start_locations::check_consistency },
             { _( "Ammunition types" ), &ammunition_type::check_consistency },
             { _( "Traps" ), &trap::check_consistency },
+            { _( "Trap migrations" ), &trap_migrations::check },
             { _( "Bionics" ), &bionic_data::check_bionic_consistency },
             { _( "Gates" ), &gates::check },
             { _( "NPC classes" ), &npc_class::check_consistency },

src/mapdata.h

@@ -746,6 +746,19 @@ class ter_furn_migrations
         static void check();
 };
 
+class trap_migrations
+{
+    public:
+        /** Handler for loading "trap_migration" type of json object */
+        static void load( const JsonObject &jo );
+
+        /** Clears migration list */
+        static void reset();
+
+        /** Checks migrations */
+        static void check();
+};
+
 class field_type_migrations
 {
     public:

src/savegame_json.cpp

@@ -4663,6 +4663,31 @@ void ter_furn_migrations::check()
     }
 }
 
+static std::unordered_map<trap_str_id, trap_str_id> tr_migrations;
+
+void trap_migrations::load( const JsonObject &jo )
+{
+    trap_str_id from_trap;
+    trap_str_id to_trap;
+    mandatory( jo, false, "from_trap", from_trap );
+    mandatory( jo, false, "to_trap", to_trap );
+    tr_migrations.insert( std::make_pair( from_trap, to_trap ) );
+}
+
+void trap_migrations::reset()
+{
+    tr_migrations.clear();
+}
+
+void trap_migrations::check()
+{
+    for( const auto &migration : tr_migrations ) {
+        if( !migration.second.is_valid() ) {
+            debugmsg( "trap_migration specifies invalid to_trap id '%s'", migration.second.c_str() );
+        }
+    }
+}
+
 static std::unordered_map<field_type_str_id, field_type_str_id> field_migrations;
 
 void field_type_migrations::load( const JsonObject &jo )