libstore: move Goal::getBuildResult to BuildResult

there are no other uses for this yet, but asking for just a subset of
outputs does seem at least somewhat useful to have as a generic thing

Change-Id: I30ff5055a666c351b1b086b8d05b9d7c9fb1c77a

1 files changed, 23 insertions, 0 deletions

diff --git a/src/libstore/build-result.cc b/src/libstore/build-result.cc
index 18f519c5c..de280c13f 100644
--- a/src/libstore/build-result.cc
+++ b/src/libstore/build-result.cc
@@ -15,4 +15,27 @@ GENERATE_CMP_EXT(
     me->cpuUser,
     me->cpuSystem);
 
+KeyedBuildResult BuildResult::restrictTo(DerivedPath path) const
+{
+    KeyedBuildResult res{*this, std::move(path)};
+
+    if (auto pbp = std::get_if<DerivedPath::Built>(&res.path)) {
+        auto & bp = *pbp;
+
+        /* Because goals are in general shared between derived paths
+           that share the same derivation, we need to filter their
+           results to get back just the results we care about.
+         */
+
+        for (auto it = res.builtOutputs.begin(); it != res.builtOutputs.end();) {
+            if (bp.outputs.contains(it->first))
+                ++it;
+            else
+                it = res.builtOutputs.erase(it);
+        }
+    }
+
+    return res;
+}
+
 }