8 files changed, 58 insertions, 2 deletions
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 2a3f1e2c3221..ce0b9e8b0bd2 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -347,6 +347,7 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
        derivation. */
     foreach (PathSet::iterator, i, context) {
         Path path = *i;
+        bool explicitlyPassed = false;
         
         /* Paths marked with `=' denote that the path of a derivation
            is explicitly passed to the builder.  Since that allows the
@@ -361,8 +362,10 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
             foreach (PathSet::iterator, j, refs) {
                 drv.inputSrcs.insert(*j);
                 if (isDerivation(*j))
-                    drv.inputDrvs[*j] = singleton<StringSet>("out");
+                    drv.inputDrvs[*j] = store -> queryDerivationOutputNames(*j);
             }
+
+            explicitlyPassed = true;
         }
 
         /* See prim_unsafeDiscardOutputDependency. */
@@ -376,7 +379,10 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
 
         debug(format("derivation uses `%1%'") % path);
         if (!useDrvAsSrc && isDerivation(path))
-            drv.inputDrvs[path] = singleton<StringSet>("out");
+            if (explicitlyPassed)
+                drv.inputDrvs[path] = store -> queryDerivationOutputNames(path);
+            else
+                drv.inputDrvs[path] = singleton<StringSet>("out");
         else
             drv.inputSrcs.insert(path);
     }
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 702ff67e793e..8ca5daa9f171 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -820,6 +820,28 @@ PathSet LocalStore::queryDerivationOutputs(const Path & path)
 }
 
 
+StringSet LocalStore::queryDerivationOutputNames(const Path & path)
+{
+    SQLiteTxn txn(db);
+    
+    SQLiteStmtUse use(stmtQueryDerivationOutputs);
+    stmtQueryDerivationOutputs.bind(queryValidPathId(path));
+    
+    StringSet outputNames;
+    int r;
+    while ((r = sqlite3_step(stmtQueryDerivationOutputs)) == SQLITE_ROW) {
+        const char * s = (const char *) sqlite3_column_text(stmtQueryDerivationOutputs, 0);
+        assert(s);
+        outputNames.insert(s);
+    }
+    
+    if (r != SQLITE_DONE)
+        throwSQLiteError(db, format("error getting output names of `%1%'") % path);
+
+    return outputNames;
+}
+
+
 void LocalStore::startSubstituter(const Path & substituter, RunningSubstituter & run)
 {
     if (run.pid != -1) return;
diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index 7ef01b2644b4..b97e2f406190 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -118,6 +118,8 @@ public:
     PathSet queryValidDerivers(const Path & path);
 
     PathSet queryDerivationOutputs(const Path & path);
+
+    StringSet queryDerivationOutputNames(const Path & path);
     
     PathSet querySubstitutablePaths();
     
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 568a6aa58a35..84c87246f0f0 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -322,6 +322,16 @@ PathSet RemoteStore::queryDerivationOutputs(const Path & path)
 }
 
 
+PathSet RemoteStore::queryDerivationOutputNames(const Path & path)
+{
+    openConnection();
+    writeInt(wopQueryDerivationOutputNames, to);
+    writeString(path, to);
+    processStderr();
+    return readStringSet(from);
+}
+
+
 Path RemoteStore::addToStore(const Path & _srcPath,
     bool recursive, HashType hashAlgo, PathFilter & filter)
 {
diff --git a/src/libstore/remote-store.hh b/src/libstore/remote-store.hh
index 519f46fd1a6d..3be9e315a219 100644
--- a/src/libstore/remote-store.hh
+++ b/src/libstore/remote-store.hh
@@ -41,6 +41,8 @@ public:
     
     PathSet queryDerivationOutputs(const Path & path);
     
+    StringSet queryDerivationOutputNames(const Path & path);
+
     bool hasSubstitutes(const Path & path);
     
     bool querySubstitutablePathInfo(const Path & path,
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index b3e67436c6c3..0384657498b5 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -140,6 +140,9 @@ public:
 
     /* Query the outputs of the derivation denoted by `path'. */
     virtual PathSet queryDerivationOutputs(const Path & path) = 0;
+
+    /* Query the output names of the derivation denoted by `path'. */
+    virtual StringSet queryDerivationOutputNames(const Path & path) = 0;
     
     /* Query whether a path has substitutes. */
     virtual bool hasSubstitutes(const Path & path) = 0;
diff --git a/src/libstore/worker-protocol.hh b/src/libstore/worker-protocol.hh
index acb8bc8b2948..576e754d2d7a 100644
--- a/src/libstore/worker-protocol.hh
+++ b/src/libstore/worker-protocol.hh
@@ -39,6 +39,7 @@ typedef enum {
     wopQueryFailedPaths = 24,
     wopClearFailedPaths = 25,
     wopQueryPathInfo = 26,
+    wopQueryDerivationOutputNames = 27,
 } WorkerOp;
 
 
diff --git a/src/nix-worker/nix-worker.cc b/src/nix-worker/nix-worker.cc
index 0fa1b40aede9..3587bd7fde2e 100644
--- a/src/nix-worker/nix-worker.cc
+++ b/src/nix-worker/nix-worker.cc
@@ -331,6 +331,16 @@ static void performOp(unsigned int clientVersion,
         break;
     }
 
+    case wopQueryDerivationOutputNames: {
+        Path path = readStorePath(from);
+        startWork();
+        StringSet names;
+        names = store->queryDerivationOutputNames(path);
+        stopWork();
+        writeStringSet(names, to);
+        break;
+    }
+
     case wopQueryDeriver: {
         Path path = readStorePath(from);
         startWork();