libstore: diagnose local build failure in goal

this should be done where we're actually trying to build something, not
in the main worker loop that shouldn't have to be aware of such details

Change-Id: I07276740c0e2e5591a8ce4828a4bfc705396527e

1 files changed, 16 insertions, 1 deletions

diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 1e3c4109d..8587ad662 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -1,6 +1,7 @@
 #include "local-derivation-goal.hh"
 #include "indirect-root-store.hh"
 #include "hook-instance.hh"
+#include "machines.hh"
 #include "store-api.hh"
 #include "worker.hh"
 #include "builtins.hh"
@@ -159,7 +160,21 @@ Goal::WorkResult LocalDerivationGoal::tryLocalBuild(bool inBuildSlot)
     if (!inBuildSlot) {
         state = &DerivationGoal::tryToBuild;
         outputLocks.unlock();
-        return WaitForSlot{};
+        if (0U != settings.maxBuildJobs) {
+            return WaitForSlot{};
+        }
+        if (getMachines().empty()) {
+            throw Error(
+                "unable to start any build; either set '--max-jobs' to a non-zero value or enable "
+                "remote builds.\n"
+                "https://docs.lix.systems/manual/lix/stable/advanced-topics/distributed-builds.html"
+            );
+        } else {
+            throw Error(
+                "unable to start any build; remote machines may not have all required system features.\n"
+                "https://docs.lix.systems/manual/lix/stable/advanced-topics/distributed-builds.html"
+            );
+        }
     }
 
     assert(derivationType);