Don't load caches when blocks/chainstate was deleted and also delete old caches (#3280)

* Don't load caches when blocks/chainstate was not present

* Delete old cache files when we decided to not load them

* Make sure cache files are of the exact format we expected them to be, flush empty objects into them instead of deleting files naively

* Streamline logic a bit, rename fIgnoreCacheFiles to fLoadCacheFiles

Co-authored-by: UdjinM6 <UdjinM6@users.noreply.github.com>

Author: codablock

src/init.cpp

@@ -2074,32 +2074,58 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
 
     // LOAD SERIALIZED DAT FILES INTO DATA CACHES FOR INTERNAL USE
 
-    bool fIgnoreCacheFiles = fLiteMode || fReindex || fReindexChainState;
-    if (!fIgnoreCacheFiles) {
-        fs::path pathDB = GetDataDir();
-        std::string strDBName;
-
-        strDBName = "mncache.dat";
-        uiInterface.InitMessage(_("Loading masternode cache..."));
-        CFlatDB<CMasternodeMetaMan> flatdb1(strDBName, "magicMasternodeCache");
+    bool fLoadCacheFiles = !(fLiteMode || fReindex || fReindexChainState);
+    {
+        LOCK(cs_main);
+        // was blocks/chainstate deleted?
+        if (chainActive.Tip() == nullptr) {
+            fLoadCacheFiles = false;
+        }
+    }
+    fs::path pathDB = GetDataDir();
+    std::string strDBName;
+
+    strDBName = "mncache.dat";
+    uiInterface.InitMessage(_("Loading masternode cache..."));
+    CFlatDB<CMasternodeMetaMan> flatdb1(strDBName, "magicMasternodeCache");
+    if (fLoadCacheFiles) {
         if(!flatdb1.Load(mmetaman)) {
             return InitError(_("Failed to load masternode cache from") + "\n" + (pathDB / strDBName).string());
         }
+    } else {
+        CMasternodeMetaMan mmetamanTmp;
+        if(!flatdb1.Dump(mmetamanTmp)) {
+            return InitError(_("Failed to clear masternode cache at") + "\n" + (pathDB / strDBName).string());
+        }
+    }
 
-        strDBName = "governance.dat";
-        uiInterface.InitMessage(_("Loading governance cache..."));
-        CFlatDB<CGovernanceManager> flatdb3(strDBName, "magicGovernanceCache");
+    strDBName = "governance.dat";
+    uiInterface.InitMessage(_("Loading governance cache..."));
+    CFlatDB<CGovernanceManager> flatdb3(strDBName, "magicGovernanceCache");
+    if (fLoadCacheFiles) {
         if(!flatdb3.Load(governance)) {
             return InitError(_("Failed to load governance cache from") + "\n" + (pathDB / strDBName).string());
         }
         governance.InitOnLoad();
+    } else {
+        CGovernanceManager governanceTmp;
+        if(!flatdb3.Dump(governanceTmp)) {
+            return InitError(_("Failed to clear governance cache at") + "\n" + (pathDB / strDBName).string());
+        }
+    }
 
-        strDBName = "netfulfilled.dat";
-        uiInterface.InitMessage(_("Loading fulfilled requests cache..."));
-        CFlatDB<CNetFulfilledRequestManager> flatdb4(strDBName, "magicFulfilledCache");
+    strDBName = "netfulfilled.dat";
+    uiInterface.InitMessage(_("Loading fulfilled requests cache..."));
+    CFlatDB<CNetFulfilledRequestManager> flatdb4(strDBName, "magicFulfilledCache");
+    if (fLoadCacheFiles) {
         if(!flatdb4.Load(netfulfilledman)) {
             return InitError(_("Failed to load fulfilled requests cache from") + "\n" + (pathDB / strDBName).string());
         }
+    } else {
+        CNetFulfilledRequestManager netfulfilledmanTmp;
+        if(!flatdb4.Dump(netfulfilledmanTmp)) {
+            return InitError(_("Failed to clear fulfilled requests cache at") + "\n" + (pathDB / strDBName).string());
+        }
     }
 
     // ********************************************************* Step 10c: schedule Dash-specific tasks