Restore subdir support in registries

Hacky...

src/libexpr/common-eval-args.cc

@@ -42,9 +42,11 @@ MixEvalArgs::MixEvalArgs()
       .description("override a flake registry value")
       .arity(2)
       .handler([&](std::vector<std::string> ss) {
-          fetchers::overrideRegistry(
-              parseFlakeRef(ss[0], absPath(".")).input,
-              parseFlakeRef(ss[1], absPath(".")).input);
+          auto from = parseFlakeRef(ss[0], absPath("."));
+          auto to = parseFlakeRef(ss[1], absPath("."));
+          fetchers::Input::Attrs extraAttrs;
+          if (to.subdir != "") extraAttrs["subdir"] = to.subdir;
+          fetchers::overrideRegistry(from.input, to.input, extraAttrs);
       });
 }
 

src/libexpr/flake/flakeref.cc

@@ -40,7 +40,8 @@ bool FlakeRef::operator ==(const FlakeRef & other) const
 
 FlakeRef FlakeRef::resolve(ref<Store> store) const
 {
-    return FlakeRef(lookupInRegistries(store, input), subdir);
+    auto [input2, extraAttrs] = lookupInRegistries(store, input);
+    return FlakeRef(input2, fetchers::maybeGetStrAttr(extraAttrs, "subdir").value_or(subdir));
 }
 
 FlakeRef parseFlakeRef(

src/libexpr/primops/fetchTree.cc

@@ -36,7 +36,7 @@ static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, V
         input = fetchers::inputFromURL(state.coerceToString(pos, *args[0], context, false, false));
 
     if (!evalSettings.pureEval && !input->isDirect())
-        input = lookupInRegistries(state.store, input);
+        input = lookupInRegistries(state.store, input).first;
 
     if (evalSettings.pureEval && !input->isImmutable())
         throw Error("in pure evaluation mode, 'fetchTree' requires an immutable input");

src/libstore/fetchers/registry.cc

@@ -29,16 +29,25 @@ std::shared_ptr<Registry> Registry::read(
                 throw Error("flake registry '%s' lacks a 'url' attribute for entry '%s'",
                     path, i.key());
             registry->entries.push_back(
-                {inputFromURL(i.key()), inputFromURL(url)});
+                {inputFromURL(i.key()), inputFromURL(url), {}});
         }
     }
 
     else if (version == 2) {
-        for (auto & i : json["flakes"])
+        for (auto & i : json["flakes"]) {
+            auto toAttrs = jsonToAttrs(i["to"]);
+            Input::Attrs extraAttrs;
+            auto j = toAttrs.find("subdir");
+            if (j != toAttrs.end()) {
+                extraAttrs.insert(*j);
+                toAttrs.erase(j);
+            }
             registry->entries.push_back(
                 { inputFromAttrs(jsonToAttrs(i["from"]))
-                , inputFromAttrs(jsonToAttrs(i["to"]))
+                , inputFromAttrs(toAttrs)
+                , extraAttrs
                 });
+        }
     }
 
     else
@@ -53,8 +62,9 @@ void Registry::write(const Path & path)
     nlohmann::json arr;
     for (auto & elem : entries) {
         nlohmann::json obj;
-        obj["from"] = attrsToJson(elem.first->toAttrs());
-        obj["to"] = attrsToJson(elem.second->toAttrs());
+        obj["from"] = attrsToJson(std::get<0>(elem)->toAttrs());
+        obj["to"] = attrsToJson(std::get<1>(elem)->toAttrs());
+        obj["to"].update(attrsToJson(std::get<2>(elem)));
         arr.emplace_back(std::move(obj));
     }
 
@@ -68,16 +78,17 @@ void Registry::write(const Path & path)
 
 void Registry::add(
     const std::shared_ptr<const Input> & from,
-    const std::shared_ptr<const Input> & to)
+    const std::shared_ptr<const Input> & to,
+    const Input::Attrs & extraAttrs)
 {
-    entries.emplace_back(from, to);
+    entries.emplace_back(from, to, extraAttrs);
 }
 
 void Registry::remove(const std::shared_ptr<const Input> & input)
 {
     // FIXME: use C++20 std::erase.
     for (auto i = entries.begin(); i != entries.end(); )
-        if (*i->first == *input)
+        if (*std::get<0>(*i) == *input)
             i = entries.erase(i);
         else
             ++i;
@@ -103,9 +114,10 @@ std::shared_ptr<Registry> getFlagRegistry()
 
 void overrideRegistry(
     const std::shared_ptr<const Input> & from,
-    const std::shared_ptr<const Input> & to)
+    const std::shared_ptr<const Input> & to,
+    const Input::Attrs & extraAttrs)
 {
-    flagRegistry->add(from, to);
+    flagRegistry->add(from, to, extraAttrs);
 }
 
 static std::shared_ptr<Registry> getGlobalRegistry(ref<Store> store)
@@ -135,10 +147,11 @@ Registries getRegistries(ref<Store> store)
     return registries;
 }
 
-std::shared_ptr<const Input> lookupInRegistries(
+std::pair<std::shared_ptr<const Input>, Input::Attrs> lookupInRegistries(
     ref<Store> store,
     std::shared_ptr<const Input> input)
 {
+    Input::Attrs extraAttrs;
     int n = 0;
 
  restart:
@@ -149,10 +162,12 @@ std::shared_ptr<const Input> lookupInRegistries(
     for (auto & registry : getRegistries(store)) {
         // FIXME: O(n)
         for (auto & entry : registry->entries) {
-            if (entry.first->contains(*input)) {
-                input = entry.second->applyOverrides(
-                    !entry.first->getRef() && input->getRef() ? input->getRef() : std::optional<std::string>(),
-                    !entry.first->getRev() && input->getRev() ? input->getRev() : std::optional<Hash>());
+            auto from = std::get<0>(entry);
+            if (from->contains(*input)) {
+                input = std::get<1>(entry)->applyOverrides(
+                    !from->getRef() && input->getRef() ? input->getRef() : std::optional<std::string>(),
+                    !from->getRev() && input->getRev() ? input->getRev() : std::optional<Hash>());
+                extraAttrs = std::get<2>(entry);
                 goto restart;
             }
         }
@@ -161,7 +176,7 @@ std::shared_ptr<const Input> lookupInRegistries(
     if (!input->isDirect())
         throw Error("cannot find flake '%s' in the flake registries", input->to_string());
 
-    return input;
+    return {input, extraAttrs};
 }
 
 }

src/libstore/fetchers/registry.hh

@@ -1,13 +1,12 @@
 #pragma once
 
 #include "types.hh"
+#include "fetchers.hh"
 
 namespace nix { class Store; }
 
 namespace nix::fetchers {
 
-struct Input;
-
 struct Registry
 {
     enum RegistryType {
@@ -18,7 +17,13 @@ struct Registry
 
     RegistryType type;
 
-    std::vector<std::pair<std::shared_ptr<const Input>, std::shared_ptr<const Input>>> entries;
+    std::vector<
+        std::tuple<
+            std::shared_ptr<const Input>, // from
+            std::shared_ptr<const Input>, // to
+            Input::Attrs // extra attributes
+            >
+        > entries;
 
     Registry(RegistryType type)
         : type(type)
@@ -31,7 +36,8 @@ struct Registry
 
     void add(
         const std::shared_ptr<const Input> & from,
-        const std::shared_ptr<const Input> & to);
+        const std::shared_ptr<const Input> & to,
+        const Input::Attrs & extraAttrs);
 
     void remove(const std::shared_ptr<const Input> & input);
 };
@@ -46,9 +52,10 @@ Registries getRegistries(ref<Store> store);
 
 void overrideRegistry(
     const std::shared_ptr<const Input> & from,
-    const std::shared_ptr<const Input> & to);
+    const std::shared_ptr<const Input> & to,
+    const Input::Attrs & extraAttrs);
 
-std::shared_ptr<const Input> lookupInRegistries(
+std::pair<std::shared_ptr<const Input>, Input::Attrs> lookupInRegistries(
     ref<Store> store,
     std::shared_ptr<const Input> input);
 

src/nix/flake.cc

@@ -70,8 +70,8 @@ struct CmdFlakeList : EvalCommand
                     registry->type == Registry::Flag ? "flags " :
                     registry->type == Registry::User ? "user  " :
                     "global",
-                    entry.first->to_string(),
-                    entry.second->to_string());
+                    std::get<0>(entry)->to_string(),
+                    std::get<1>(entry)->to_string());
             }
         }
     }
@@ -506,9 +506,11 @@ struct CmdFlakeAdd : MixEvalArgs, Command
     {
         auto fromRef = parseFlakeRef(fromUrl);
         auto toRef = parseFlakeRef(toUrl);
+        fetchers::Input::Attrs extraAttrs;
+        if (toRef.subdir != "") extraAttrs["subdir"] = toRef.subdir;
         auto userRegistry = fetchers::getUserRegistry();
         userRegistry->remove(fromRef.input);
-        userRegistry->add(fromRef.input, toRef.input);
+        userRegistry->add(fromRef.input, toRef.input, extraAttrs);
         userRegistry->write(fetchers::getUserRegistryPath());
     }
 };
@@ -555,7 +557,9 @@ struct CmdFlakePin : virtual Args, EvalCommand
         auto userRegistry = fetchers::getUserRegistry();
         userRegistry->remove(ref.input);
         auto [tree, resolved] = ref.resolve(store).input->fetchTree(store);
-        userRegistry->add(ref.input, resolved);
+        fetchers::Input::Attrs extraAttrs;
+        if (ref.subdir != "") extraAttrs["subdir"] = ref.subdir;
+        userRegistry->add(ref.input, resolved, extraAttrs);
     }
 };