Merge bitcoin/bitcoin#15936: interfaces: Expose settings.json methods to GUI

f9fdcec7e932843a91ddf7f377e00bd2a6efb82a settings: Add resetSettings() method (Ryan Ofsky)
77fabffef4ea840ee15c97061048fe8443d74658 init: Remove Shutdown() node.args reset (Ryan Ofsky)
0e55bc6e7fe439404dc56093a0949395dae51e6b settings: Add update/getPersistent/isIgnored methods (Ryan Ofsky)

Pull request description:

  Add `interfaces::Node` `updateSetting`, `forceSetting`, `resetSettings`, `isSettingIgnored`, and `getPersistentSetting` methods so GUI is able to manipulate `settings.json` file and use and modify node settings.

  (Originally this PR also contained GUI changes to unify bitcoin-qt and bitcoind persistent settings and call these methods, but the GUI commits have been dropped from this PR and moved to bitcoin-core/gui/pull/602)

ACKs for top commit:
  vasild:
    ACK f9fdcec7e932843a91ddf7f377e00bd2a6efb82a
  hebasto:
    re-ACK f9fdcec7e932843a91ddf7f377e00bd2a6efb82a, only a function renamed since my recent [review](https://github.com/bitcoin/bitcoin/pull/15936#pullrequestreview-979324357).

Tree-SHA512: 4cac853ee29be96d2ff38404165b9dfb7c622b2a9c99a15979596f3484ffde0da3d9c9c372677dff5119ca7cffa6383d81037fd9889a29cc9285882a8dc0c268

1 files changed, 31 insertions, 4 deletions

diff --git a/src/util/system.cpp b/src/util/system.cpp
index 6a07139d93..f88b0fac77 100644
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -530,12 +530,15 @@ bool ArgsManager::InitSettings(std::string& error)
     return true;
 }
 
-bool ArgsManager::GetSettingsPath(fs::path* filepath, bool temp) const
+bool ArgsManager::GetSettingsPath(fs::path* filepath, bool temp, bool backup) const
 {
     fs::path settings = GetPathArg("-settings", fs::path{BITCOIN_SETTINGS_FILENAME});
     if (settings.empty()) {
         return false;
     }
+    if (backup) {
+        settings += ".bak";
+    }
     if (filepath) {
         *filepath = fsbridge::AbsPathJoin(GetDataDirNet(), temp ? settings + ".tmp" : settings);
     }
@@ -576,10 +579,10 @@ bool ArgsManager::ReadSettingsFile(std::vector<std::string>* errors)
     return true;
 }
 
-bool ArgsManager::WriteSettingsFile(std::vector<std::string>* errors) const
+bool ArgsManager::WriteSettingsFile(std::vector<std::string>* errors, bool backup) const
 {
     fs::path path, path_tmp;
-    if (!GetSettingsPath(&path, /* temp= */ false) || !GetSettingsPath(&path_tmp, /* temp= */ true)) {
+    if (!GetSettingsPath(&path, /*temp=*/false, backup) || !GetSettingsPath(&path_tmp, /*temp=*/true, backup)) {
         throw std::logic_error("Attempt to write settings file when dynamic settings are disabled.");
     }
 
@@ -596,6 +599,13 @@ bool ArgsManager::WriteSettingsFile(std::vector<std::string>* errors) const
     return true;
 }
 
+util::SettingsValue ArgsManager::GetPersistentSetting(const std::string& name) const
+{
+    LOCK(cs_args);
+    return util::GetSetting(m_settings, m_network, name, !UseDefaultSection("-" + name),
+        /*ignore_nonpersistent=*/true, /*get_chain_name=*/false);
+}
+
 bool ArgsManager::IsArgNegated(const std::string& strArg) const
 {
     return GetSetting(strArg).isFalse();
@@ -604,18 +614,33 @@ bool ArgsManager::IsArgNegated(const std::string& strArg) const
 std::string ArgsManager::GetArg(const std::string& strArg, const std::string& strDefault) const
 {
     const util::SettingsValue value = GetSetting(strArg);
+    return SettingToString(value, strDefault);
+}
+
+std::string SettingToString(const util::SettingsValue& value, const std::string& strDefault)
+{
     return value.isNull() ? strDefault : value.isFalse() ? "0" : value.isTrue() ? "1" : value.isNum() ? value.getValStr() : value.get_str();
 }
 
 int64_t ArgsManager::GetIntArg(const std::string& strArg, int64_t nDefault) const
 {
     const util::SettingsValue value = GetSetting(strArg);
+    return SettingToInt(value, nDefault);
+}
+
+int64_t SettingToInt(const util::SettingsValue& value, int64_t nDefault)
+{
     return value.isNull() ? nDefault : value.isFalse() ? 0 : value.isTrue() ? 1 : value.isNum() ? value.getInt<int64_t>() : LocaleIndependentAtoi<int64_t>(value.get_str());
 }
 
 bool ArgsManager::GetBoolArg(const std::string& strArg, bool fDefault) const
 {
     const util::SettingsValue value = GetSetting(strArg);
+    return SettingToBool(value, fDefault);
+}
+
+bool SettingToBool(const util::SettingsValue& value, bool fDefault)
+{
     return value.isNull() ? fDefault : value.isBool() ? value.get_bool() : InterpretBool(value.get_str());
 }
 
@@ -1006,6 +1031,7 @@ std::string ArgsManager::GetChainName() const
         LOCK(cs_args);
         util::SettingsValue value = util::GetSetting(m_settings, /* section= */ "", SettingName(arg),
             /* ignore_default_section_config= */ false,
+            /*ignore_nonpersistent=*/false,
             /* get_chain_name= */ true);
         return value.isNull() ? false : value.isBool() ? value.get_bool() : InterpretBool(value.get_str());
     };
@@ -1038,7 +1064,8 @@ util::SettingsValue ArgsManager::GetSetting(const std::string& arg) const
 {
     LOCK(cs_args);
     return util::GetSetting(
-        m_settings, m_network, SettingName(arg), !UseDefaultSection(arg), /* get_chain_name= */ false);
+        m_settings, m_network, SettingName(arg), !UseDefaultSection(arg),
+        /*ignore_nonpersistent=*/false, /*get_chain_name=*/false);
 }
 
 std::vector<util::SettingsValue> ArgsManager::GetSettingsList(const std::string& arg) const