8 files changed, 97 insertions, 12 deletions
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 66173cdaf05f..dc361c043f67 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -347,6 +347,8 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
        derivation. */
     foreach (PathSet::iterator, i, context) {
         Path path = *i;
+        bool explicitlyPassed = false;
+        string output = "out";
         
         /* Paths marked with `=' denote that the path of a derivation
            is explicitly passed to the builder.  Since that allows the
@@ -361,8 +363,15 @@ 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;
+        } else if (path.at(0) == '!') {
+            size_t index;
+            path = string(path, 1);
+            index = path.find("!");
+            output = path.substr(0, index);
+            path = string(path, index + 1);
         }
 
         /* See prim_unsafeDiscardOutputDependency. */
@@ -376,7 +385,12 @@ 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 if (drv.inputDrvs.find(path) == drv.inputDrvs.end())
+                drv.inputDrvs[path] = singleton<StringSet>(output);
+            else
+                drv.inputDrvs[path].insert(output);
         else
             drv.inputSrcs.insert(path);
     }
@@ -450,7 +464,7 @@ static void prim_derivationStrict(EvalState & state, Value * * args, Value & v)
         /* The output path of an output X is ‘<X>Path’,
            e.g. ‘outPath’. */
         mkString(*state.allocAttr(v, state.symbols.create(i->first + "Path")),
-            i->second.path, singleton<PathSet>(drvPath));
+            i->second.path, singleton<PathSet>("!" + i->first + "!" + drvPath));
     }
     v.attrs->sort();
 }
@@ -1042,15 +1056,6 @@ void EvalState::createBaseEnv()
     addPrimOp("__getEnv", 1, prim_getEnv);
     addPrimOp("__trace", 2, prim_trace);
 
-    // Derivations
-    addPrimOp("derivationStrict", 1, prim_derivationStrict);
-
-    /* Add a wrapper around the derivation primop that computes the
-       `drvPath' and `outPath' attributes lazily. */
-    string s = "attrs: let res = derivationStrict attrs; in attrs // { drvPath = res.drvPath; outPath = res.outPath; type = \"derivation\"; }";
-    mkThunk_(v, parseExprFromString(s, "/"));
-    addConstant("derivation", v);
-
     // Paths
     addPrimOp("__toPath", 1, prim_toPath);
     addPrimOp("__storePath", 1, prim_storePath);
@@ -1099,6 +1104,36 @@ void EvalState::createBaseEnv()
     addPrimOp("__parseDrvName", 1, prim_parseDrvName);
     addPrimOp("__compareVersions", 2, prim_compareVersions);
 
+    // Derivations
+    addPrimOp("derivationStrict", 1, prim_derivationStrict);
+
+    /* Add a wrapper around the derivation primop that computes the
+       `drvPath' and `outPath' attributes lazily. */
+    string s = "attrs: \
+      let \
+        strict = derivationStrict attrs; \
+        attrValues = attrs: \
+          map (name: builtins.getAttr name attrs) (builtins.attrNames attrs); \
+        outputToAttrListElement = output: \
+          { \
+            name = output; \
+            value = attrs // { \
+              outPath = builtins.getAttr (output + \"Path\") strict; \
+              drvPath = strict.drvPath; \
+              type = \"derivation\"; \
+              currentOutput = output; \
+            } // outputsAttrs // { all = allList; }; \
+          }; \
+        outputsList = if attrs ? outputs then \
+          map outputToAttrListElement attrs.outputs else \
+          [ (outputToAttrListElement \"out\") ]; \
+        outputsAttrs = builtins.listToAttrs outputsList; \
+        allList = attrValues outputsAttrs; \
+        head = if attrs ? outputs then builtins.head attrs.outputs else \"out\"; \
+      in builtins.getAttr head outputsAttrs";
+    mkThunk_(v, parseExprFromString(s, "/"));
+    addConstant("derivation", v);
+
     /* Now that we've added all primops, sort the `builtins' attribute
        set, because attribute lookups expect it to be sorted. */
     baseEnv.values[0]->attrs->sort();
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index cf0e2ad1b13b..29817df9d6e8 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 4cb905f67231..2739c4eea69d 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 942c5bcf1c7c..ce99c205e7d0 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -326,6 +326,16 @@ 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 34a2d91dfcd1..c5853ef53646 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 d4997c886207..14890f5225ad 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 760d08a747ae..ef1e0993df28 100644
--- a/src/libstore/worker-protocol.hh
+++ b/src/libstore/worker-protocol.hh
@@ -39,6 +39,7 @@ typedef enum {
     wopClearFailedPaths = 25,
     wopQueryPathInfo = 26,
     wopImportPaths = 27,
+    wopQueryDerivationOutputNames = 28,
 } WorkerOp;
 
 
diff --git a/src/nix-worker/nix-worker.cc b/src/nix-worker/nix-worker.cc
index 5f57b2981d9a..68567f341e05 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();