Modularize config settings

Allow global config settings to be defined in multiple Config
classes. For example, this means that libutil can have settings and
evaluator settings can be moved out of libstore. The Config classes
are registered in a new GlobalConfig class to which config files
etc. are applied.

Relevant to https://github.com/NixOS/nix/issues/2009 in that it
removes the need for ad hoc handling of useCaseHack, which was the
underlying cause of that issue.

2 files changed, 9 insertions, 6 deletions

diff --git a/src/nix/main.cc b/src/nix/main.cc
index bb107ec7d3f6..9cd5d21c84b6 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -34,9 +34,10 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
             .handler([&]() {
                 std::cout << "The following configuration options are available:\n\n";
                 Table2 tbl;
-                for (const auto & s : settings._getSettings())
-                    if (!s.second.isAlias)
-                        tbl.emplace_back(s.first, s.second.setting->description);
+                std::map<std::string, Config::SettingInfo> settings;
+                globalConfig.getSettings(settings);
+                for (const auto & s : settings)
+                    tbl.emplace_back(s.first, s.second.description);
                 printTable(std::cout, tbl);
                 throw Exit();
             });
diff --git a/src/nix/show-config.cc b/src/nix/show-config.cc
index c64b12c8dd62..86638b50d2c6 100644
--- a/src/nix/show-config.cc
+++ b/src/nix/show-config.cc
@@ -27,10 +27,12 @@ struct CmdShowConfig : Command, MixJSON
         if (json) {
             // FIXME: use appropriate JSON types (bool, ints, etc).
             JSONObject jsonObj(std::cout);
-            settings.toJSON(jsonObj);
+            globalConfig.toJSON(jsonObj);
         } else {
-            for (auto & s : settings.getSettings())
-                std::cout << s.first + " = " + s.second + "\n";
+            std::map<std::string, Config::SettingInfo> settings;
+            globalConfig.getSettings(settings);
+            for (auto & s : settings)
+                std::cout << s.first + " = " + s.second.value + "\n";
         }
     }
 };