Move getAccessorCached() to InputCache

Also, make fetchTree use InputCache.

src/libexpr/primops/fetchTree.cc

@@ -10,6 +10,7 @@
 #include "nix/util/url.hh"
 #include "nix/expr/value-to-json.hh"
 #include "nix/fetchers/fetch-to-store.hh"
+#include "nix/fetchers/input-cache.hh"
 #include "nix/util/mounted-source-accessor.hh"
 
 #include <nlohmann/json.hpp>
@@ -201,16 +202,15 @@ static void fetchTree(
             throw Error("input '%s' is not allowed to use the '__final' attribute", input.to_string());
     }
 
-    // FIXME: use fetchOrSubstituteTree().
+    auto cachedInput = fetchers::InputCache::getCache()->getAccessor(state.store, input, false);
-    auto [accessor, lockedInput] = input.getAccessor(state.store);
 
     auto storePath = StorePath::random(input.getName());
 
     state.allowPath(storePath);
 
-    state.storeFS->mount(CanonPath(state.store->printStorePath(storePath)), accessor);
+    state.storeFS->mount(CanonPath(state.store->printStorePath(storePath)), cachedInput.accessor);
 
-    emitTreeAttrs(state, storePath, lockedInput, v, params.emptyRevFallback, false);
+    emitTreeAttrs(state, storePath, cachedInput.lockedInput, v, params.emptyRevFallback, false);
 }
 
 static void prim_fetchTree(EvalState & state, const PosIdx pos, Value * * args, Value & v)

src/libfetchers/include/nix/fetchers/input-cache.hh

@@ -2,14 +2,23 @@
 
 namespace nix::fetchers {
 
-struct CachedInput
-{
-    Input lockedInput;
-    ref<SourceAccessor> accessor;
-};
-
 struct InputCache
 {
+    struct CachedResult
+    {
+        ref<SourceAccessor> accessor;
+        Input resolvedInput;
+        Input lockedInput;
+    };
+
+    CachedResult getAccessor(ref<Store> store, const Input & originalInput, bool useRegistries);
+
+    struct CachedInput
+    {
+        Input lockedInput;
+        ref<SourceAccessor> accessor;
+    };
+
     virtual std::optional<CachedInput> lookup(const Input & originalInput) const = 0;
 
     virtual void upsert(Input key, CachedInput cachedInput) = 0;

src/libfetchers/input-cache.cc

@@ -1,8 +1,48 @@
 #include "nix/fetchers/input-cache.hh"
+#include "nix/fetchers/registry.hh"
 #include "nix/util/sync.hh"
+#include "nix/util/source-path.hh"
 
 namespace nix::fetchers {
 
+InputCache::CachedResult InputCache::getAccessor(ref<Store> store, const Input & originalInput, bool useRegistries)
+{
+    auto fetched = lookup(originalInput);
+    Input resolvedInput = originalInput;
+
+    if (!fetched) {
+        if (originalInput.isDirect()) {
+            auto [accessor, lockedInput] = originalInput.getAccessor(store);
+            fetched.emplace(CachedInput{.lockedInput = lockedInput, .accessor = accessor});
+        } else {
+            if (useRegistries) {
+                auto [res, extraAttrs] =
+                    lookupInRegistries(store, originalInput, [](fetchers::Registry::RegistryType type) {
+                        /* Only use the global registry and CLI flags
+                           to resolve indirect flakerefs. */
+                        return type == fetchers::Registry::Flag || type == fetchers::Registry::Global;
+                    });
+                resolvedInput = std::move(res);
+                fetched = lookup(resolvedInput);
+                if (!fetched) {
+                    auto [accessor, lockedInput] = resolvedInput.getAccessor(store);
+                    fetched.emplace(CachedInput{.lockedInput = lockedInput, .accessor = accessor});
+                }
+                upsert(resolvedInput, *fetched);
+            } else {
+                throw Error(
+                    "'%s' is an indirect flake reference, but registry lookups are not allowed",
+                    originalInput.to_string());
+            }
+        }
+        upsert(originalInput, *fetched);
+    }
+
+    debug("got tree '%s' from '%s'", fetched->accessor, fetched->lockedInput.to_string());
+
+    return {fetched->accessor, resolvedInput, fetched->lockedInput};
+}
+
 struct InputCacheImpl : InputCache
 {
     Sync<std::map<Input, CachedInput>> cache_;

src/libflake/flake/flake.cc

@@ -26,48 +26,6 @@ using namespace fetchers;
 
 namespace flake {
 
-static std::tuple<ref<SourceAccessor>, Input, Input> getAccessorCached(
-    EvalState & state,
-    const Input & originalInput,
-    bool useRegistries)
-{
-    auto inputCache = InputCache::getCache();
-
-    auto fetched = inputCache->lookup(originalInput);
-    Input resolvedInput = originalInput;
-
-    if (!fetched) {
-        if (originalInput.isDirect()) {
-            auto [accessor, lockedInput] = originalInput.getAccessor(state.store);
-            fetched.emplace(CachedInput{.lockedInput = lockedInput, .accessor = accessor});
-        } else {
-            if (useRegistries) {
-                auto [res, extraAttrs] = lookupInRegistries(state.store, originalInput,
-                    [](fetchers::Registry::RegistryType type) {
-                        /* Only use the global registry and CLI flags
-                           to resolve indirect flakerefs. */
-                        return type == fetchers::Registry::Flag || type == fetchers::Registry::Global;
-                    });
-                resolvedInput = std::move(res);
-                fetched = inputCache->lookup(resolvedInput);
-                if (!fetched) {
-                    auto [accessor, lockedInput] = resolvedInput.getAccessor(state.store);
-                    fetched.emplace(CachedInput{.lockedInput = lockedInput, .accessor = accessor});
-                }
-                inputCache->upsert(resolvedInput, *fetched);
-            }
-            else {
-                throw Error("'%s' is an indirect flake reference, but registry lookups are not allowed", originalInput.to_string());
-            }
-        }
-        inputCache->upsert(originalInput, *fetched);
-    }
-
-    debug("got tree '%s' from '%s'", fetched->accessor, fetched->lockedInput.to_string());
-
-    return {fetched->accessor, resolvedInput, fetched->lockedInput};
-}
-
 static StorePath mountInput(
     EvalState & state,
     fetchers::Input & input,
@@ -395,14 +353,13 @@ static Flake getFlake(
     CopyMode copyMode)
 {
     // Fetch a lazy tree first.
-    auto [accessor, resolvedInput, lockedInput] = getAccessorCached(
+    auto cachedInput = fetchers::InputCache::getCache()->getAccessor(state.store, originalRef.input, useRegistries);
-        state, originalRef.input, useRegistries);
 
-    auto resolvedRef = FlakeRef(std::move(resolvedInput), originalRef.subdir);
+    auto resolvedRef = FlakeRef(std::move(cachedInput.resolvedInput), originalRef.subdir);
-    auto lockedRef = FlakeRef(std::move(lockedInput), originalRef.subdir);
+    auto lockedRef = FlakeRef(std::move(cachedInput.lockedInput), originalRef.subdir);
 
     // Parse/eval flake.nix to get at the input.self attributes.
-    auto flake = readFlake(state, originalRef, resolvedRef, lockedRef, {accessor}, lockRootAttrPath);
+    auto flake = readFlake(state, originalRef, resolvedRef, lockedRef, {cachedInput.accessor}, lockRootAttrPath);
 
     // Re-fetch the tree if necessary.
     auto newLockedRef = applySelfAttrs(lockedRef, flake);
@@ -411,16 +368,15 @@ static Flake getFlake(
         debug("refetching input '%s' due to self attribute", newLockedRef);
         // FIXME: need to remove attrs that are invalidated by the changed input attrs, such as 'narHash'.
         newLockedRef.input.attrs.erase("narHash");
-        auto [accessor2, resolvedInput2, lockedInput2] = getAccessorCached(
+        auto cachedInput2 = fetchers::InputCache::getCache()->getAccessor(state.store, newLockedRef.input, useRegistries);
-            state, newLockedRef.input, false);
+        cachedInput.accessor = cachedInput2.accessor;
-        accessor = accessor2;
+        lockedRef = FlakeRef(std::move(cachedInput2.lockedInput), newLockedRef.subdir);
-        lockedRef = FlakeRef(std::move(lockedInput2), newLockedRef.subdir);
     }
 
     // Re-parse flake.nix from the store.
     return readFlake(
         state, originalRef, resolvedRef, lockedRef,
-        state.storePath(mountInput(state, lockedRef.input, originalRef.input, accessor, copyMode)),
+        state.storePath(mountInput(state, lockedRef.input, originalRef.input, cachedInput.accessor, copyMode)),
         lockRootAttrPath);
 }
 
@@ -778,13 +734,12 @@ LockedFlake lockFlake(
                                 if (auto resolvedPath = resolveRelativePath()) {
                                     return {*resolvedPath, *input.ref};
                                 } else {
-                                    auto [accessor, resolvedInput, lockedInput] = getAccessorCached(
+                                    auto cachedInput = fetchers::InputCache::getCache()->getAccessor(state.store, input.ref->input, useRegistries);
-                                        state, input.ref->input, useRegistries);
 
-                                    auto lockedRef = FlakeRef(std::move(lockedInput), input.ref->subdir);
+                                    auto lockedRef = FlakeRef(std::move(cachedInput.lockedInput), input.ref->subdir);
 
                                     return {
-                                        state.storePath(mountInput(state, lockedRef.input, input.ref->input, accessor, inputCopyMode)),
+                                        state.storePath(mountInput(state, lockedRef.input, input.ref->input, cachedInput.accessor, inputCopyMode)),
                                         lockedRef
                                     };
                                 }