Avoid wallet code writing node settings file

Change wallet loading code to access settings through the Chain
interface instead of writing settings.json directly.

src/interfaces/chain.h

@@ -262,11 +262,18 @@ public:
     //! Current RPC serialization flags.
     virtual int rpcSerializationFlags() = 0;
 
+    //! Get settings value.
+    virtual util::SettingsValue getSetting(const std::string& arg) = 0;
+
+    //! Get list of settings values.
+    virtual std::vector<util::SettingsValue> getSettingsList(const std::string& arg) = 0;
+
     //! Return <datadir>/settings.json setting value.
     virtual util::SettingsValue getRwSetting(const std::string& name) = 0;
 
-    //! Write a setting to <datadir>/settings.json.
+    //! Write a setting to <datadir>/settings.json. Optionally just update the
-    virtual bool updateRwSetting(const std::string& name, const util::SettingsValue& value) = 0;
+    //! setting in memory and do not write the file.
+    virtual bool updateRwSetting(const std::string& name, const util::SettingsValue& value, bool write=true) = 0;
 
     //! Synchronously send transactionAddedToMempool notifications about all
     //! current mempool transactions to the specified handler and return after

src/node/interfaces.cpp

@@ -690,6 +690,14 @@ public:
         RPCRunLater(name, std::move(fn), seconds);
     }
     int rpcSerializationFlags() override { return RPCSerializationFlags(); }
+    util::SettingsValue getSetting(const std::string& name) override
+    {
+        return gArgs.GetSetting(name);
+    }
+    std::vector<util::SettingsValue> getSettingsList(const std::string& name) override
+    {
+        return gArgs.GetSettingsList(name);
+    }
     util::SettingsValue getRwSetting(const std::string& name) override
     {
         util::SettingsValue result;
@@ -700,7 +708,7 @@ public:
         });
         return result;
     }
-    bool updateRwSetting(const std::string& name, const util::SettingsValue& value) override
+    bool updateRwSetting(const std::string& name, const util::SettingsValue& value, bool write) override
     {
         gArgs.LockSettings([&](util::Settings& settings) {
             if (value.isNull()) {
@@ -709,7 +717,7 @@ public:
                 settings.rw_settings[name] = value;
             }
         });
-        return gArgs.WriteSettingsFile();
+        return !write || gArgs.WriteSettingsFile();
     }
     void requestMempoolTransactions(Notifications& notifications) override
     {

src/util/system.h

@@ -207,6 +207,7 @@ protected:
      */
     bool UseDefaultSection(const std::string& arg) const EXCLUSIVE_LOCKS_REQUIRED(cs_args);
 
+ public:
     /**
      * Get setting value.
      *
@@ -221,7 +222,6 @@ protected:
      */
     std::vector<util::SettingsValue> GetSettingsList(const std::string& arg) const;
 
-public:
     ArgsManager();
     ~ArgsManager();
 

src/wallet/load.cpp

@@ -50,18 +50,20 @@ bool VerifyWallets(interfaces::Chain& chain)
         options.require_existing = true;
         options.verify = false;
         if (MakeWalletDatabase("", options, status, error_string)) {
-            gArgs.LockSettings([&](util::Settings& settings) {
             util::SettingsValue wallets(util::SettingsValue::VARR);
             wallets.push_back(""); // Default wallet name is ""
-                settings.rw_settings["wallet"] = wallets;
+            // Pass write=false because no need to write file and probably
-            });
+            // better not to. If unnamed wallet needs to be added next startup
+            // and the setting is empty, this code will just run again.
+            chain.updateRwSetting("wallet", wallets, /* write= */ false);
         }
     }
 
     // Keep track of each wallet absolute path to detect duplicates.
     std::set<fs::path> wallet_paths;
 
-    for (const auto& wallet_file : gArgs.GetArgs("-wallet")) {
+    for (const auto& wallet : chain.getSettingsList("wallet")) {
+        const auto& wallet_file = wallet.get_str();
         const fs::path path = fsbridge::AbsPathJoin(GetWalletDir(), wallet_file);
 
         if (!wallet_paths.insert(path).second) {
@@ -91,7 +93,8 @@ bool LoadWallets(interfaces::Chain& chain)
 {
     try {
         std::set<fs::path> wallet_paths;
-        for (const std::string& name : gArgs.GetArgs("-wallet")) {
+        for (const auto& wallet : chain.getSettingsList("wallet")) {
+            const auto& name = wallet.get_str();
             if (!wallet_paths.insert(name).second) {
                 continue;
             }