addPath: allow paths with references

Since 4806f2f6b0, we can't have paths with
references passed to builtins.{path,filterSource}. This prevents many cases
of those functions called on IFD outputs from working. Resolve this by
passing the references found in the original path to the added path.

src/libexpr/primops.cc

@@ -1859,12 +1859,12 @@ static void addPath(
         // be rewritten to the actual output).
         state.realiseContext(context);
 
+        StorePathSet refs = StorePathSet();
+
         if (state.store->isInStore(path)) {
             auto [storePath, subPath] = state.store->toStorePath(path);
-            auto info = state.store->queryPathInfo(storePath);
+            // FIXME: we should scanForReferences on the path before adding it
-            if (!info->references.empty())
+            refs = state.store->queryPathInfo(storePath)->references;
-                throw EvalError("store path '%s' is not allowed to have references",
-                    state.store->printStorePath(storePath));
             path = state.store->toRealPath(storePath) + subPath;
         }
 
@@ -1904,7 +1904,7 @@ static void addPath(
         if (!expectedHash || !state.store->isValidPath(*expectedStorePath)) {
             dstPath = state.store->printStorePath(settings.readOnlyMode
                 ? state.store->computeStorePathForPath(name, path, method, htSHA256, filter).first
-                : state.store->addToStore(name, path, method, htSHA256, filter, state.repair));
+                : state.store->addToStore(name, path, method, htSHA256, filter, state.repair, refs));
             if (expectedHash && expectedStorePath != state.store->parseStorePath(dstPath))
                 throw Error("store path mismatch in (possibly filtered) path added from '%s'", path);
         } else

src/libstore/binary-cache-store.cc

@@ -314,7 +314,7 @@ StorePath BinaryCacheStore::addToStoreFromDump(Source & dump, const string & nam
         unsupported("addToStoreFromDump");
     return addToStoreCommon(dump, repair, CheckSigs, [&](HashResult nar) {
         ValidPathInfo info {
-            makeFixedOutputPath(method, nar.first, name),
+            makeFixedOutputPath(method, nar.first, name, references),
             nar.first,
         };
         info.narSize = nar.second;
@@ -405,7 +405,7 @@ StorePath BinaryCacheStore::addToStore(const string & name, const Path & srcPath
     });
     return addToStoreCommon(*source, repair, CheckSigs, [&](HashResult nar) {
         ValidPathInfo info {
-            makeFixedOutputPath(method, h, name),
+            makeFixedOutputPath(method, h, name, references),
             nar.first,
         };
         info.narSize = nar.second;

src/libstore/daemon.cc

@@ -402,8 +402,6 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
                         return store->queryPathInfo(path);
                     },
                     [&](FixedOutputHashMethod & fohm) {
-                        // if (!refs.empty())
-                            // throw UnimplementedError("cannot yet have refs with flat or nar-hashed data");
                         auto path = store->addToStoreFromDump(source, name, fohm.fileIngestionMethod, fohm.hashType, repair, refs);
                         return store->queryPathInfo(path);
                     },

src/libstore/local-store.cc

@@ -1358,7 +1358,7 @@ StorePath LocalStore::addToStoreFromDump(Source & source0, const string & name,
 
     auto [hash, size] = hashSink->finish();
 
-    auto dstPath = makeFixedOutputPath(method, hash, name);
+    auto dstPath = makeFixedOutputPath(method, hash, name, references);
 
     addTempRoot(dstPath);