From ac5081d28035ef8d6a907fc3bff812d534719f74 Mon Sep 17 00:00:00 2001
From: Robert Hensing <robert@roberthensing.nl>
Date: Fri, 13 Nov 2020 17:49:27 +0100
Subject: [PATCH] nix-build: Fix #4197 output order regression

---
 src/nix-build/nix-build.cc | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/nix-build/nix-build.cc b/src/nix-build/nix-build.cc
index f60e0706c..74fafd426 100755
--- a/src/nix-build/nix-build.cc
+++ b/src/nix-build/nix-build.cc
@@ -487,6 +487,7 @@ static void main_nix_build(int argc, char * * argv)
     else {
 
         std::vector<StorePathWithOutputs> pathsToBuild;
+        std::vector<std::pair<StorePath, std::string>> pathsToBuildOrdered;
 
         std::map<StorePath, std::pair<size_t, StringSet>> drvMap;
 
@@ -498,6 +499,7 @@ static void main_nix_build(int argc, char * * argv)
                 throw Error("derivation '%s' lacks an 'outputName' attribute", store->printStorePath(drvPath));
 
             pathsToBuild.push_back({drvPath, {outputName}});
+            pathsToBuildOrdered.push_back({drvPath, {outputName}});
 
             auto i = drvMap.find(drvPath);
             if (i != drvMap.end())
@@ -513,25 +515,23 @@ static void main_nix_build(int argc, char * * argv)
 
         std::vector<StorePath> outPaths;
 
-        for (auto & [drvPath, info] : drvMap) {
-            auto & [counter, wantedOutputs] = info;
+        for (auto & [drvPath, outputName] : pathsToBuildOrdered) {
+            auto & [counter, _wantedOutputs] = drvMap.at({drvPath});
             std::string drvPrefix = outLink;
             if (counter)
                 drvPrefix += fmt("-%d", counter + 1);
 
             auto builtOutputs = store->queryDerivationOutputMap(drvPath);
 
-            for (auto & outputName : wantedOutputs) {
-                auto outputPath = builtOutputs.at(outputName);
+            auto outputPath = builtOutputs.at(outputName);
 
-                if (auto store2 = store.dynamic_pointer_cast<LocalFSStore>()) {
-                    std::string symlink = drvPrefix;
-                    if (outputName != "out") symlink += "-" + outputName;
-                    store2->addPermRoot(outputPath, absPath(symlink));
-                }
-
-                outPaths.push_back(outputPath);
+            if (auto store2 = store.dynamic_pointer_cast<LocalFSStore>()) {
+                std::string symlink = drvPrefix;
+                if (outputName != "out") symlink += "-" + outputName;
+                store2->addPermRoot(outputPath, absPath(symlink));
             }
+
+            outPaths.push_back(outputPath);
         }
 
         logger->stop();