Make the store plugins more introspectable

Directly register the store classes rather than a function to build an
instance of them.
This gives the possibility to introspect static members of the class or
choose different ways of instantiating them.

1 files changed, 30 insertions, 0 deletions

diff --git a/src/nix/describe-stores.cc b/src/nix/describe-stores.cc
new file mode 100644
index 000000000..d84378316
--- /dev/null
+++ b/src/nix/describe-stores.cc
@@ -0,0 +1,30 @@
+#include "command.hh"
+#include "common-args.hh"
+#include "shared.hh"
+#include "store-api.hh"
+
+#include <nlohmann/json.hpp>
+
+using namespace nix;
+
+struct CmdDescribeStores : Command, MixJSON
+{
+    std::string description() override
+    {
+        return "show registered store types and their available options";
+    }
+
+    Category category() override { return catUtility; }
+
+    void run() override
+    {
+
+        if (json) {
+            auto availableStores = *implementations;
+        } else {
+            throw Error("Only json is available for describe-stores");
+        }
+    }
+};
+
+static auto r1 = registerCommand<CmdDescribeStores>("describe-stores");