Read per-user settings from ~/.config/nix/nix.conf

src/libutil/config.cc

@@ -9,6 +9,7 @@ void Config::set(const std::string & name, const std::string & value)
     if (i == _settings.end())
         throw UsageError("unknown setting '%s'", name);
     i->second.setting->set(value);
+    i->second.setting->overriden = true;
 }
 
 void Config::addSetting(AbstractSetting * setting)
@@ -22,6 +23,7 @@ void Config::addSetting(AbstractSetting * setting)
     auto i = initials.find(setting->name);
     if (i != initials.end()) {
         setting->set(i->second);
+        setting->overriden = true;
         initials.erase(i);
         set = true;
     }
@@ -34,6 +36,7 @@ void Config::addSetting(AbstractSetting * setting)
                     alias, setting->name);
             else {
                 setting->set(i->second);
+                setting->overriden = true;
                 initials.erase(i);
                 set = true;
             }
@@ -47,11 +50,11 @@ void Config::warnUnknownSettings()
         warn("unknown setting '%s'", i.first);
 }
 
-StringMap Config::getSettings()
+StringMap Config::getSettings(bool overridenOnly)
 {
     StringMap res;
     for (auto & opt : _settings)
-        if (!opt.second.isAlias)
+        if (!opt.second.isAlias && (!overridenOnly || opt.second.setting->overriden))
             res.emplace(opt.first, opt.second.setting->to_string());
     return res;
 }
@@ -94,6 +97,12 @@ void Config::applyConfigFile(const Path & path, bool fatal)
     } catch (SysError &) { }
 }
 
+void Config::resetOverriden()
+{
+    for (auto & s : _settings)
+        s.second.setting->overriden = false;
+}
+
 AbstractSetting::AbstractSetting(
     const std::string & name,
     const std::string & description,

src/libutil/config.hh

@@ -51,9 +51,11 @@ public:
 
     void warnUnknownSettings();
 
-    StringMap getSettings();
+    StringMap getSettings(bool overridenOnly = false);
 
     void applyConfigFile(const Path & path, bool fatal = false);
+
+    void resetOverriden();
 };
 
 class AbstractSetting
@@ -68,6 +70,8 @@ public:
 
     int created = 123;
 
+    bool overriden = false;
+
 protected:
 
     AbstractSetting(
@@ -78,7 +82,7 @@ protected:
     virtual ~AbstractSetting()
     {
         // Check against a gcc miscompilation causing our constructor
-        // not to run.
+        // not to run (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80431).
         assert(created == 123);
     }
 
@@ -88,6 +92,8 @@ protected:
 
     bool parseBool(const std::string & str);
     std::string printBool(bool b);
+
+    bool isOverriden() { return overriden; }
 };
 
 struct DefaultSettingTag { };

src/libutil/util.cc

@@ -429,6 +429,18 @@ Path getCacheDir()
 }
 
 
+Path getConfigDir()
+{
+    Path configDir = getEnv("XDG_CONFIG_HOME");
+    if (configDir.empty()) {
+        Path homeDir = getEnv("HOME");
+        if (homeDir.empty()) throw Error("$XDG_CONFIG_HOME and $HOME are not set");
+        configDir = homeDir + "/.config";
+    }
+    return configDir;
+}
+
+
 Paths createDirs(const Path & path)
 {
     Paths created;

src/libutil/util.hh

@@ -110,9 +110,12 @@ void deletePath(const Path & path, unsigned long long & bytesFreed);
 Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix",
     bool includePid = true, bool useGlobalCounter = true, mode_t mode = 0755);
 
-/* Return the path to $XDG_CACHE_HOME/.cache. */
+/* Return $XDG_CACHE_HOME or $HOME/.cache. */
 Path getCacheDir();
 
+/* Return $XDG_CONFIG_HOME or $HOME/.config. */
+Path getConfigDir();
+
 /* Create a directory and all its parents, if necessary.  Returns the
    list of created directories, in order of creation. */
 Paths createDirs(const Path & path);