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

doc/manual/command-ref/conf-file.xml

@@ -17,13 +17,32 @@
 
 <refsection><title>Description</title>
 
-<para>A number of persistent settings of Nix are stored in the file
-<filename><replaceable>sysconfdir</replaceable>/nix/nix.conf</filename> or
-<filename>$NIX_CONF_DIR/nix.conf</filename> if <envar>NIX_CONF_DIR</envar> is set.
-This file is a list of <literal><replaceable>name</replaceable> =
+<para>Nix reads settings from two configuration files:</para>
+
+<itemizedlist>
+
+  <listitem>
+    <para>The system-wide configuration file
+    <filename><replaceable>sysconfdir</replaceable>/nix/nix.conf</filename>
+    (i.e. <filename>/etc/nix/nix.conf</filename> on most systems), or
+    <filename>$NIX_CONF_DIR/nix.conf</filename> if
+    <envar>NIX_CONF_DIR</envar> is set.</para>
+  </listitem>
+
+  <listitem>
+    <para>The user configuration file
+    <filename>$XDG_CONFIG_HOME/nix/nix.conf</filename>, or
+    <filename>~/.config/nix/nix.conf</filename> if
+    <envar>XDG_CONFIG_HOME</envar> is not set.</para>
+  </listitem>
+
+</itemizedlist>
+
+<para>The configuration files consist of
+<literal><replaceable>name</replaceable> =
 <replaceable>value</replaceable></literal> pairs, one per line.
-Comments start with a <literal>#</literal> character.  Here is an example
-configuration file:</para>
+Comments start with a <literal>#</literal> character.  Here is an
+example configuration file:</para>
 
 <programlisting>
 gc-keep-outputs = true       # Nice for developers
@@ -31,8 +50,9 @@ gc-keep-derivations = true   # Idem
 env-keep-derivations = false
 </programlisting>
 
-<para>You can override settings using the <option>--option</option>
-flag, e.g. <literal>--option gc-keep-outputs false</literal>.</para>
+<para>You can override settings on the command line using the
+<option>--option</option> flag, e.g. <literal>--option gc-keep-outputs
+false</literal>.</para>
 
 <para>The following settings are currently available:
 

src/libstore/globals.cc

@@ -53,19 +53,19 @@ Settings::Settings()
 void Settings::loadConfFile()
 {
     applyConfigFile(nixConfDir + "/nix.conf");
+
+    /* We only want to send overrides to the daemon, i.e. stuff from
+       ~/.nix/nix.conf or the command line. */
+    resetOverriden();
+
+    applyConfigFile(getConfigDir() + "/nix/nix.conf");
 }
 
 void Settings::set(const string & name, const string & value)
 {
-    overrides[name] = value;
     Config::set(name, value);
 }
 
-StringMap Settings::getOverrides()
-{
-    return overrides;
-}
-
 unsigned int Settings::getDefaultCores()
 {
     return std::max(1U, std::thread::hardware_concurrency());

src/libstore/globals.hh

@@ -15,8 +15,6 @@ extern bool useCaseHack; // FIXME
 
 class Settings : public Config {
 
-    StringMap overrides;
-
     unsigned int getDefaultCores();
 
 public:
@@ -27,8 +25,6 @@ public:
 
     void set(const string & name, const string & value);
 
-    StringMap getOverrides();
-
     Path nixPrefix;
 
     /* The directory where we store sources and derived files. */

src/libstore/remote-store.cc

@@ -166,7 +166,7 @@ void RemoteStore::setOptions(Connection & conn)
        << settings.useSubstitutes;
 
     if (GET_PROTOCOL_MINOR(conn.daemonVersion) >= 12) {
-        StringMap overrides = settings.getOverrides();
+        auto overrides = settings.getSettings(true);
         conn.to << overrides.size();
         for (auto & i : overrides)
             conn.to << i.first << i.second;

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);