Don't substitute derivations that have preferLocalBuild set

In particular this means that "trivial" derivations such as writeText
are not substituted, reducing the number of GET requests to the binary
cache by about 200 on a typical NixOS configuration.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index 74ff26b9cc5c..1bf3f9378245 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -120,7 +120,8 @@ void queryMissing(StoreAPI & store, const PathSet & targets,
                 if (invalid.empty()) continue;
 
                 todoDrv.insert(*i);
-                if (settings.useSubstitutes) query.insert(invalid.begin(), invalid.end());
+                if (settings.useSubstitutes && !willBuildLocally(drv))
+                    query.insert(invalid.begin(), invalid.end());
             }
 
             else {
@@ -143,7 +144,7 @@ void queryMissing(StoreAPI & store, const PathSet & targets,
 
             PathSet outputs;
             bool mustBuild = false;
-            if (settings.useSubstitutes) {
+            if (settings.useSubstitutes && !willBuildLocally(drv)) {
                 foreach (DerivationOutputs::iterator, j, drv.outputs) {
                     if (!wantOutput(j->first, i2.second)) continue;
                     if (!store.isValidPath(j->second.path)) {