util: add ArgsManager datadir helper functions

* Add ArgsManager::EnsureDataDir()
  Creates data directory if it doesn't exist
* Add ArgsManager::GetConfigFilePath()
  Return config file path (read-only)

Author: willcl-ark

src/util/system.cpp

@@ -446,6 +446,27 @@ const fs::path& ArgsManager::GetDataDir(bool net_specific) const
     return path;
 }
 
+void ArgsManager::EnsureDataDir() const
+{
+    /**
+     * "/wallets" subdirectories are created in all **new**
+     * datadirs, because wallet code will create new wallets in the "wallets"
+     * subdirectory only if exists already, otherwise it will create them in
+     * the top-level datadir where they could interfere with other files.
+     * Wallet init code currently avoids creating "wallets" directories itself
+     * for backwards compatibility, but this be changed in the future and
+     * wallet code here could go away (#16220).
+     */
+    auto path{GetDataDir(false)};
+    if (!fs::exists(path)) {
+        fs::create_directories(path / "wallets");
+    }
+    path = GetDataDir(true);
+    if (!fs::exists(path)) {
+        fs::create_directories(path / "wallets");
+    }
+}
+
 void ArgsManager::ClearPathCache()
 {
     LOCK(cs_args);
@@ -965,6 +986,11 @@ bool ArgsManager::ReadConfigStream(std::istream& stream, const std::string& file
     return true;
 }
 
+fs::path ArgsManager::GetConfigFilePath() const
+{
+    return GetConfigFile(GetPathArg("-conf", BITCOIN_CONF_FILENAME));
+}
+
 bool ArgsManager::ReadConfigFiles(std::string& error, bool ignore_invalid_keys)
 {
     {

src/util/system.h

@@ -242,6 +242,11 @@ class ArgsManager
     void SelectConfigNetwork(const std::string& network);
 
     [[nodiscard]] bool ParseParameters(int argc, const char* const argv[], std::string& error);
+
+    /**
+     * Return config file path (read-only)
+     */
+    fs::path GetConfigFilePath() const;
     [[nodiscard]] bool ReadConfigFiles(std::string& error, bool ignore_invalid_keys = false);
 
     /**
@@ -475,6 +480,12 @@ class ArgsManager
      */
     void LogArgs() const;
 
+    /**
+     * If datadir does not exist, create it along with wallets/
+     * subdirectory(s).
+     */
+    void EnsureDataDir() const;
+
 private:
     /**
      * Get data directory path