Allow to draw produced-item icons in recipe dialog and game world

src/test/ConfigLoaderTest.cpp

@@ -390,6 +390,39 @@ duration_seconds = 1.0
         std::runtime_error);
 }
 
+TEST_CASE("Optional recipe icon field parses; absent leaves it unset", "[config]")
+{
+    TempConfigDir dir;
+    writeFile(dir.path() / "recipes.toml", R"(
+[[recipe]]
+id = "with_icon"
+building = "assembler"
+inputs = [{item = "iron_ingot", amount = 1}]
+outputs = [{item = "steel_plate", amount = 1}]
+duration_seconds = 1.0
+icon = "hardened_steel"
+
+[[recipe]]
+id = "without_icon"
+building = "assembler"
+inputs = [{item = "iron_ingot", amount = 1}]
+outputs = [{item = "copper_wire", amount = 1}]
+duration_seconds = 1.0
+)");
+
+    const RecipesConfig cfg =
+        ConfigLoader::loadRecipes((dir.path() / "recipes.toml").string());
+
+    const RecipeDef& withIcon = cfg.recipes.at(0);
+    REQUIRE(withIcon.id == "with_icon");
+    REQUIRE(withIcon.icon.has_value());
+    REQUIRE(*withIcon.icon == "hardened_steel");
+
+    const RecipeDef& withoutIcon = cfg.recipes.at(1);
+    REQUIRE(withoutIcon.id == "without_icon");
+    REQUIRE_FALSE(withoutIcon.icon.has_value());
+}
+
 // --- unlock_requires (REQ-LOCK-PREREQ) ------------------------------------
 
 namespace