importPaths(): Fix accessor support for Hydra

src/libstore/binary-cache-store.cc

@@ -318,4 +318,12 @@ ref<FSAccessor> BinaryCacheStore::getFSAccessor()
             std::dynamic_pointer_cast<BinaryCacheStore>(shared_from_this())));
 }
 
+void BinaryCacheStore::addPathToAccessor(ref<FSAccessor> accessor,
+    const Path & storePath, const ref<std::string> & data)
+{
+    auto accessor_ = accessor.dynamic_pointer_cast<BinaryCacheStoreAccessor>();
+    if (accessor_)
+        accessor_->nars.emplace(storePath, makeNarAccessor(data));
+}
+
 }

src/libstore/binary-cache-store.hh

@@ -134,6 +134,12 @@ public:
 
     ref<FSAccessor> getFSAccessor() override;
 
+private:
+
+    void addPathToAccessor(ref<FSAccessor>, const Path & storePath, const ref<std::string> & data) override;
+
+public:
+
     void addSignatures(const Path & storePath, const StringSet & sigs) override
     { notImpl(); }
 

src/libstore/export-import.cc

@@ -119,13 +119,8 @@ Paths Store::importPaths(Source & source, std::shared_ptr<FSAccessor> accessor,
 
         addToStore(info, *tee.data, false, dontCheckSigs);
 
-        // FIXME: implement accessors?
-        assert(!accessor);
-#if 0
-        auto accessor_ = std::dynamic_pointer_cast<BinaryCacheStoreAccessor>(accessor);
-        if (accessor_)
-            accessor_->nars.emplace(info.path, makeNarAccessor(tee.data));
-#endif
+        if (accessor)
+            addPathToAccessor(ref<FSAccessor>(accessor), info.path, tee.data);
 
         res.push_back(info.path);
     }

src/libstore/store-api.hh

@@ -461,6 +461,17 @@ public:
     /* Return an object to access files in the Nix store. */
     virtual ref<FSAccessor> getFSAccessor() = 0;
 
+private:
+
+    /* Inform an accessor about the NAR contents of a store path. Used
+       by importPaths() to speed up subsequent access to the imported
+       paths when used with binary cache stores. */
+    virtual void addPathToAccessor(ref<FSAccessor>, const Path & storePath, const ref<std::string> & data)
+    {
+    }
+
+public:
+
     /* Add signatures to the specified store path. The signatures are
        not verified. */
     virtual void addSignatures(const Path & storePath, const StringSet & sigs) = 0;