libstore: fix build tests

the new event loop could very occasionally notice that a dependency of
some goal has failed, process the failure, cause the depending goal to
fail accordingly, and in the doing of the latter two steps let further
dependencies that previously have not been reported as failed do their
reporting anyway. in such cases a goal could fail with "1 dependencies
failed", but more than one dependency failure message was shown. we'll
now report the correct number of failed dependency goals in all cases.

Change-Id: I5aa95dcb2db4de4fd5fee8acbf5db833531d81a8

1 files changed, 11 insertions, 7 deletions

diff --git a/src/libstore/build/goal.cc b/src/libstore/build/goal.cc
index 8a2f4ab35..5f0ed485c 100644
--- a/src/libstore/build/goal.cc
+++ b/src/libstore/build/goal.cc
@@ -33,18 +33,22 @@ kj::Promise<Result<Goal::WorkResult>>
 Goal::waitForGoals(kj::Array<std::pair<GoalPtr, kj::Promise<void>>> dependencies) noexcept
 try {
     auto left = dependencies.size();
+    for (auto & [dep, p] : dependencies) {
+        p = p.then([this, dep, &left] {
+            left--;
+            trace(fmt("waitee '%s' done; %d left", dep->name, left));
+
+            if (dep->exitCode != Goal::ecSuccess) ++nrFailed;
+            if (dep->exitCode == Goal::ecNoSubstituters) ++nrNoSubstituters;
+            if (dep->exitCode == Goal::ecIncompleteClosure) ++nrIncompleteClosure;
+        }).eagerlyEvaluate(nullptr);
+    }
+
     auto collectDeps = asyncCollect(std::move(dependencies));
 
     while (auto item = co_await collectDeps.next()) {
-        left--;
         auto & dep = *item;
 
-        trace(fmt("waitee '%s' done; %d left", dep->name, left));
-
-        if (dep->exitCode != Goal::ecSuccess) ++nrFailed;
-        if (dep->exitCode == Goal::ecNoSubstituters) ++nrNoSubstituters;
-        if (dep->exitCode == Goal::ecIncompleteClosure) ++nrIncompleteClosure;
-
         waiteeDone(dep);
 
         if (dep->exitCode == ecFailed && !settings.keepGoing) {