Migrate -upnp and -natpmp settings from QSettings to settings.json

This also effectively reverts 58e8364dcd from
#18077, applying upnp and natpmp settings from the optionsmodel class instead
of the optionsdialog class. This makes sense because model code, not view code
is responsible for applying all other settings, and because leaving these
settings half-applied in optionsmodel seems error prone and could lead to bugs.
(These things were discussed a little in
https://github.com/bitcoin/bitcoin/pull/18077#discussion_r560381734)

src/qt/optionsdialog.cpp

@@ -26,7 +26,6 @@
 #include <QIntValidator>
 #include <QLocale>
 #include <QMessageBox>
-#include <QSettings>
 #include <QSystemTrayIcon>
 #include <QTimer>
 
@@ -56,10 +55,6 @@ OptionsDialog::OptionsDialog(QWidget *parent, bool enableWallet) :
 #ifndef USE_NATPMP
     ui->mapPortNatpmp->setEnabled(false);
 #endif
-    connect(this, &QDialog::accepted, [this](){
-        QSettings settings;
-        model->node().mapPort(settings.value("fUseUPnP").toBool(), settings.value("fUseNatpmp").toBool());
-    });
 
     ui->proxyIp->setEnabled(false);
     ui->proxyPort->setEnabled(false);

src/qt/optionsmodel.cpp

@@ -41,6 +41,8 @@ static const char* SettingName(OptionsModel::OptionID option)
     case OptionsModel::ThreadsScriptVerif: return "par";
     case OptionsModel::SpendZeroConfChange: return "spendzeroconfchange";
     case OptionsModel::ExternalSignerPath: return "signer";
+    case OptionsModel::MapPortUPnP: return "upnp";
+    case OptionsModel::MapPortNatpmp: return "natpmp";
     default: throw std::logic_error(strprintf("GUI option %i has no corresponding node setting.", option));
     }
 }
@@ -128,7 +130,8 @@ bool OptionsModel::Init(bilingual_str& error)
 
     // These are shared with the core or have a command-line parameter
     // and we want command-line parameters to overwrite the GUI settings.
-    for (OptionID option : {DatabaseCache, ThreadsScriptVerif, SpendZeroConfChange, ExternalSignerPath}) {
+    for (OptionID option : {DatabaseCache, ThreadsScriptVerif, SpendZeroConfChange, ExternalSignerPath, MapPortUPnP,
+                            MapPortNatpmp}) {
         std::string setting = SettingName(option);
         if (node().isSettingIgnored(setting)) addOverriddenOption("-" + setting);
         try {
@@ -165,18 +168,6 @@ bool OptionsModel::Init(bilingual_str& error)
 #endif
 
     // Network
-    if (!settings.contains("fUseUPnP"))
-        settings.setValue("fUseUPnP", DEFAULT_UPNP);
-    if (!gArgs.SoftSetBoolArg("-upnp", settings.value("fUseUPnP").toBool()))
-        addOverriddenOption("-upnp");
-
-    if (!settings.contains("fUseNatpmp")) {
-        settings.setValue("fUseNatpmp", DEFAULT_NATPMP);
-    }
-    if (!gArgs.SoftSetBoolArg("-natpmp", settings.value("fUseNatpmp").toBool())) {
-        addOverriddenOption("-natpmp");
-    }
-
     if (!settings.contains("fListen"))
         settings.setValue("fListen", DEFAULT_LISTEN);
     const bool listen{settings.value("fListen").toBool()};
@@ -390,13 +381,13 @@ QVariant OptionsModel::getOption(OptionID option) const
         return fMinimizeToTray;
     case MapPortUPnP:
 #ifdef USE_UPNP
-        return settings.value("fUseUPnP");
+        return SettingToBool(setting(), DEFAULT_UPNP);
 #else
         return false;
 #endif // USE_UPNP
     case MapPortNatpmp:
 #ifdef USE_NATPMP
-        return settings.value("fUseNatpmp");
+        return SettingToBool(setting(), DEFAULT_NATPMP);
 #else
         return false;
 #endif // USE_NATPMP
@@ -478,10 +469,16 @@ bool OptionsModel::setOption(OptionID option, const QVariant& value)
         settings.setValue("fMinimizeToTray", fMinimizeToTray);
         break;
     case MapPortUPnP: // core option - can be changed on-the-fly
-        settings.setValue("fUseUPnP", value.toBool());
+        if (changed()) {
+            update(value.toBool());
+            node().mapPort(value.toBool(), getOption(MapPortNatpmp).toBool());
+        }
         break;
     case MapPortNatpmp: // core option - can be changed on-the-fly
-        settings.setValue("fUseNatpmp", value.toBool());
+        if (changed()) {
+            update(value.toBool());
+            node().mapPort(getOption(MapPortUPnP).toBool(), value.toBool());
+        }
         break;
     case MinimizeOnClose:
         fMinimizeOnClose = value.toBool();
@@ -698,4 +695,6 @@ void OptionsModel::checkAndMigrate()
     migrate_setting(SpendZeroConfChange, "bSpendZeroConfChange");
     migrate_setting(ExternalSignerPath, "external_signer_path");
 #endif
+    migrate_setting(MapPortUPnP, "fUseUPnP");
+    migrate_setting(MapPortNatpmp, "fUseNatpmp");
 }

src/qt/test/optiontests.cpp

@@ -34,6 +34,7 @@ void OptionTests::migrateSettings()
     QSettings settings;
     settings.setValue("nDatabaseCache", 600);
     settings.setValue("nThreadsScriptVerif", 12);
+    settings.setValue("fUseUPnP", false);
 
     settings.sync();
 
@@ -42,6 +43,7 @@ void OptionTests::migrateSettings()
     QVERIFY(options.Init(error));
     QVERIFY(!settings.contains("nDatabaseCache"));
     QVERIFY(!settings.contains("nThreadsScriptVerif"));
+    QVERIFY(!settings.contains("fUseUPnP"));
 
     std::ifstream file(gArgs.GetDataDirNet() / "settings.json");
     QCOMPARE(std::string(std::istreambuf_iterator<char>(file), std::istreambuf_iterator<char>()).c_str(), "{\n"