TBTR: Add template replacement index validation to CheckCaches

src/openttd.cpp

@@ -1863,6 +1863,14 @@ void CheckCaches(bool force_check, std::function<void(const char *)> log, CheckC
 			if (tv->Next()) assert_msg(tv->Next()->Prev() == tv, "%u", tv->index);
 		}
 
+		{
+			extern std::string ValidateTemplateReplacementCaches();
+			std::string template_validation_result = ValidateTemplateReplacementCaches();
+			if (!template_validation_result.empty()) {
+				CCLOG("Template replacement cache validation failed: %s", template_validation_result.c_str());
+			}
+		}
+
 		if (!TraceRestrictSlot::ValidateVehicleIndex()) CCLOG("Trace restrict slot vehicle index validation failed");
 		TraceRestrictSlot::ValidateSlotOccupants(log);
 

src/tbtr_template_vehicle.cpp

@@ -35,6 +35,8 @@
 
 #include "3rdparty/robin_hood/robin_hood.h"
 
+#include <functional>
+
 #include "safeguards.h"
 
 TemplatePool _template_pool("TemplatePool");
@@ -330,3 +332,21 @@ void ReindexTemplateReplacementsRecursive()
 		}
 	}
 }
+
+std::string ValidateTemplateReplacementCaches()
+{
+	robin_hood::unordered_flat_map<GroupID, TemplateID> saved_template_replacement_index = std::move(_template_replacement_index);
+	robin_hood::unordered_flat_map<GroupID, TemplateID> saved_template_replacement_index_recursive = std::move(_template_replacement_index_recursive);
+
+	ReindexTemplateReplacements();
+
+	bool match = (saved_template_replacement_index == _template_replacement_index);
+	bool match_recursive = (saved_template_replacement_index_recursive == _template_replacement_index_recursive);
+	_template_replacement_index = std::move(saved_template_replacement_index);
+	_template_replacement_index_recursive = std::move(saved_template_replacement_index_recursive);
+
+	if (!match) return "Index cache does not match";
+	if (!match_recursive) return "Recursive index cache does not match";
+
+	return "";
+}