Test case

data/mods/TEST_DATA/furniture.json

@@ -65,6 +65,16 @@
     "required_str": 8,
     "hacksaw": { "duration": "80 minutes" }
   },
+  {
+    "type": "furniture",
+    "id": "test_f_migration_new_id",
+    "name": "Furniture Test Migration",
+    "description": "Id to test migration from it's invalid counterparts test_t_migration_old_id and test_f_migration_old_id to.",
+    "symbol": "f",
+    "color": "blue",
+    "move_cost_mod": 1,
+    "required_str": 8
+  },
   {
     "type": "furniture",
     "id": "test_f_oxytorch1",

data/mods/TEST_DATA/ter_furn_migration.json

@@ -0,0 +1,13 @@
+[
+  {
+    "type": "ter_furn_transform",
+    "from_ter": "test_t_migration_old_id",
+    "to_ter": "test_t_migration_new_id",
+    "to_furn": "test_f_migration_new_id"
+  },
+  {
+    "type": "ter_furn_transform",
+    "from_ter": "test_f_migration_old_id",
+    "to_furn": "test_f_migration_new_id"
+  }
+]

data/mods/TEST_DATA/terrain.json

@@ -135,6 +135,16 @@
     },
     "prying": { "result": "t_grass", "duration": "30 seconds", "prying_data": { "difficulty": 100, "breakable": true } }
   },
+  {
+    "type": "terrain",
+    "id": "test_t_migration_new_id",
+    "name": "Terrain Test Migration",
+    "description": "Id to test migration from it's invalid counterpart test_t_migration_old_id to.",
+    "symbol": "t",
+    "color": "blue",
+    "move_cost": 1,
+    "bash": { "sound": "thump", "ter_set": "t_null", "str_min": 50, "str_max": 100, "str_min_supported": 100, "bash_below": true }
+  },
   {
     "type": "terrain",
     "id": "test_t_bash_persist",

tests/submap_load_test.cpp

@@ -27,6 +27,11 @@
 static const construction_str_id construction_constr_ground_cable( "constr_ground_cable" );
 static const construction_str_id construction_constr_rack_coat( "constr_rack_coat" );
 
+static const furn_str_id furn_test_f_migration_new_id( "test_f_migration_new_id" );
+
+static const ter_str_id ter_t_dirt( "t_dirt" );
+static const ter_str_id ter_test_t_migration_new_id( "test_t_migration_new_id" );
+
 // NOLINTNEXTLINE(cata-static-declarations)
 extern const int savegame_version;
 
@@ -767,6 +772,29 @@ static std::string submap_cosmetic_ss(
     "  \"computers\": [ ]\n"
     "}\n"
 );
+static std::string submap_pre_migration_ss(
+    "{\n"
+    "  \"version\": 32,\n"
+    "  \"coordinates\": [ 0, 0, 0 ],\n"
+    "  \"turn_last_touched\": 0,\n"
+    "  \"temperature\": 0,\n"
+    "  \"terrain\": [ [ \"test_t_migration_old_id\", 1, \"t_dirt\", 10, \"test_t_migration_old_id\", 1, \"t_dirt\", 132 ] ],\n"
+    "  \"radiation\": [ 0, 144 ],\n"
+    "  \"furniture\": [\n"
+    "    [ 0, 0, \"f_bookcase\" ],\n"
+    "    [ 0, 11, \"test_f_migration_old_id\" ],\n"
+    "    [ 11, 11, \"test_f_migration_old_id\" ],\n"
+    "  ],\n"
+    "  \"items\": [ ],\n"
+    "  \"traps\": [ ],\n"
+    "  \"fields\": [ ],\n"
+    "  \"cosmetics\": [ ],\n"
+    "  \"spawns\": [ ],\n"
+    "  \"vehicles\": [ ],\n"
+    "  \"partial_constructions\": [ ],\n"
+    "  \"computers\": [ ]\n"
+    "}\n"
+);
 
 static_assert( SEEX == 12, "Reminder to update submap tests when SEEX changes." );
 static_assert( SEEY == 12, "Reminder to update submap tests when SEEY changes." );
@@ -786,6 +814,8 @@ static JsonValue submap_vehicle = json_loader::from_string( submap_vehicle_ss );
 static JsonValue submap_construction = json_loader::from_string( submap_construction_ss );
 static JsonValue submap_computer = json_loader::from_string( submap_computer_ss );
 static JsonValue submap_cosmetic = json_loader::from_string( submap_cosmetic_ss );
+static JsonValue submap_pre_migration = json_loader::from_string( submap_pre_migration_ss );
+static JsonValue submap_post_migration = json_loader::from_string( submap_post_migration_ss );
 
 static void load_from_jsin( submap &sm, const JsonValue &jsin )
 {
@@ -1407,3 +1437,46 @@ TEST_CASE( "submap_computer_load", "[submap][load]" )
     REQUIRE( sm.has_computer( point_south ) );
     REQUIRE( sm.has_computer( {3, 5} ) );
 }
+
+TEST_CASE( "submap_ter_furn_migration", "[submap][load]" )
+{
+    submap sm;
+    load_from_jsin( sm, submap_pre_migration );
+    submap_checks checks;
+    checks.terrain = false;
+    checks.furniture = false;
+
+    REQUIRE( is_normal_submap( sm, checks ) );
+
+    const ter_id ter_nw = sm.get_ter( corner_nw );
+    const ter_id ter_ne = sm.get_ter( corner_ne );
+    const ter_id ter_sw = sm.get_ter( corner_sw );
+    const ter_id ter_se = sm.get_ter( corner_se );
+
+    const furn_id furn_nw = sm.get_furn( corner_nw );
+    const furn_id furn_ne = sm.get_furn( corner_ne );
+    const furn_id furn_sw = sm.get_furn( corner_sw );
+    const furn_id furn_se = sm.get_furn( corner_se );
+
+    // North corners should have migrated from test_t_migration_old_id to test_t_migration_new_id
+    INFO( string_format( "ter nw: %s", ter_nw.id().str() ) );
+    INFO( string_format( "ter ne: %s", ter_ne.id().str() ) );
+    REQUIRE( ter_nw == ter_test_t_migration_new_id );
+    REQUIRE( ter_ne == ter_test_t_migration_new_id );
+    // West one should still have a f_bookcase as it overrides the test_f_migration_new_id placed by migration
+    INFO( string_format( "furn nw: %s", furn_nw.id().str() ) );
+    REQUIRE( furn_nw == furn_test_f_migration_new_id );
+    // East one should now have test_f_migration_new_id as per the migration
+    INFO( string_format( "furn ne: %s", furn_ne.id().str() ) );
+    REQUIRE( furn_ne == furn_test_f_migration_new_id );
+    // South corners should still have t_dirt
+    INFO( string_format( "ter sw: %s", ter_sw.id().str() ) );
+    INFO( string_format( "ter se: %s", ter_se.id().str() ) );
+    REQUIRE( ter_sw == ter_t_dirt );
+    REQUIRE( ter_se == ter_t_dirt );
+    // But should have migrated test_f_migration_old_id to test_f_migration_new_id
+    INFO( string_format( "furn sw: %s", furn_sw.id().str() ) );
+    INFO( string_format( "furn se: %s", furn_se.id().str() ) );
+    REQUIRE( furn_sw == furn_test_f_migration_new_id );
+    REQUIRE( furn_se == furn_test_f_migration_new_id );
+}