Handle situtation where techtree.json is missing

src/TechTree.cpp

@@ -19,7 +19,13 @@ void TechTree::onStart()
     solution at the time. Hopefully the JSON-files are still up to date. */
 
     TechTreeImproved tree;
-    tree.LoadData();
+    bool success = tree.LoadData();
+
+    // If the file was not successfully open/parsed, don't replace the unitTypeData.
+    if (!success)
+    {
+        return;
+    }
 
     for (std::pair<const UnitType, TypeData> & pair : m_unitTypeData)
     {

src/TechTreeImproved.cpp

@@ -112,13 +112,20 @@ void TechTreeImproved::parse_unit(json::iterator it)
     producer_to_data[producer_id] = build_descriptions;
 }
 
-void TechTreeImproved::LoadData() {
-    // TODO: Do not hardcode this. Use the latest json available.
-    // TODO: Check if file exists
+bool TechTreeImproved::LoadData() {
     std::ifstream i("techtree.json");
+
+    if (!i.good())
+    {
+        std::wcerr << "File techtree.json cannot be found, information regarding addons and required buildings will not be up to date. Please put techtree.json in working directory." << std::endl;
+        return false;
+    }
+
+    // Parse the file's content
     json j;
     i >> j;
 
+    // Time to parse content of the JSON file
     for (auto & race : j)
     {
         for (json::iterator it = race.begin(); it != race.end(); ++it)
@@ -126,6 +133,7 @@ void TechTreeImproved::LoadData() {
             parse_unit(it);
         }
     }
+    return true;
 }
 
 const std::vector<BuildDescription> & TechTreeImproved::HowToBuild(sc2::UnitTypeID unit) const

src/TechTreeImproved.h

@@ -31,7 +31,7 @@ class TechTreeImproved
     void parse_unit(nlohmann::json::iterator it);
 public:
     TechTreeImproved();
-    void LoadData();
+    bool LoadData();
     // Given a unit, how can we build it?
     const std::vector<BuildDescription> & HowToBuild(sc2::UnitTypeID unit) const;
 };
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