From 8c7661da0963a6a578605374cd9b309177563b3d Mon Sep 17 00:00:00 2001
From: Taeer Bar-Yam <taeer.bar-yam@tweag.io>
Date: Mon, 5 Dec 2022 23:21:58 -0500
Subject: [PATCH 1/2] check the store for input before failing (hopefully fix
 #6383)

---
 src/libstore/build/derivation-goal.cc | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index 5aed51bcd..7dd39051b 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -1016,11 +1016,20 @@ void DerivationGoal::resolvedFinished()
                 throw Error(
                     "derivation '%s' doesn't have expected output '%s' (derivation-goal.cc/resolvedFinished,resolve)",
                     worker.store.printStorePath(drvPath), wantedOutput);
-            auto realisation = get(resolvedResult.builtOutputs, DrvOutput { *resolvedHash, wantedOutput });
-            if (!realisation)
+
+            const Realisation * realisation = get(resolvedResult.builtOutputs, DrvOutput { *resolvedHash, wantedOutput });
+            if (!realisation) {
+              /* The above `get` should work. But sateful tracking of
+                 outputs in resolvedResult, this can get out of sync with the
+                 store, which is our actual source of truth. For now we just
+                 check the store directly if it fails. */
+              realisation = worker.evalStore.queryRealisation(DrvOutput { *resolvedHash, wantedOutput }).get();
+              if (!realisation) {
                 throw Error(
                     "derivation '%s' doesn't have expected output '%s' (derivation-goal.cc/resolvedFinished,realisation)",
                     worker.store.printStorePath(resolvedDrvGoal->drvPath), wantedOutput);
+              }
+            }
             if (drv->type().isPure()) {
                 auto newRealisation = *realisation;
                 newRealisation.id = DrvOutput { initialOutput->outputHash, wantedOutput };

From 1c8de7d3d03d7a6ba259387b0698874fa879428c Mon Sep 17 00:00:00 2001
From: Taeer Bar-Yam <taeer.bar-yam@tweag.io>
Date: Tue, 6 Dec 2022 11:25:38 -0500
Subject: [PATCH 2/2] improve style

---
 src/libstore/build/derivation-goal.cc | 29 +++++++++++++++------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index 7dd39051b..1f9bfaae0 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -1017,30 +1017,33 @@ void DerivationGoal::resolvedFinished()
                     "derivation '%s' doesn't have expected output '%s' (derivation-goal.cc/resolvedFinished,resolve)",
                     worker.store.printStorePath(drvPath), wantedOutput);
 
-            const Realisation * realisation = get(resolvedResult.builtOutputs, DrvOutput { *resolvedHash, wantedOutput });
-            if (!realisation) {
+            auto realisation = [&]{
+              auto take1 = get(resolvedResult.builtOutputs, DrvOutput { *resolvedHash, wantedOutput });
+              if (take1) return *take1;
+
               /* The above `get` should work. But sateful tracking of
                  outputs in resolvedResult, this can get out of sync with the
                  store, which is our actual source of truth. For now we just
                  check the store directly if it fails. */
-              realisation = worker.evalStore.queryRealisation(DrvOutput { *resolvedHash, wantedOutput }).get();
-              if (!realisation) {
-                throw Error(
-                    "derivation '%s' doesn't have expected output '%s' (derivation-goal.cc/resolvedFinished,realisation)",
-                    worker.store.printStorePath(resolvedDrvGoal->drvPath), wantedOutput);
-              }
-            }
+              auto take2 = worker.evalStore.queryRealisation(DrvOutput { *resolvedHash, wantedOutput });
+              if (take2) return *take2;
+
+              throw Error(
+                  "derivation '%s' doesn't have expected output '%s' (derivation-goal.cc/resolvedFinished,realisation)",
+                  worker.store.printStorePath(resolvedDrvGoal->drvPath), wantedOutput);
+            }();
+
             if (drv->type().isPure()) {
-                auto newRealisation = *realisation;
+                auto newRealisation = realisation;
                 newRealisation.id = DrvOutput { initialOutput->outputHash, wantedOutput };
                 newRealisation.signatures.clear();
                 if (!drv->type().isFixed())
-                    newRealisation.dependentRealisations = drvOutputReferences(worker.store, *drv, realisation->outPath);
+                    newRealisation.dependentRealisations = drvOutputReferences(worker.store, *drv, realisation.outPath);
                 signRealisation(newRealisation);
                 worker.store.registerDrvOutput(newRealisation);
             }
-            outputPaths.insert(realisation->outPath);
-            builtOutputs.emplace(realisation->id, *realisation);
+            outputPaths.insert(realisation.outPath);
+            builtOutputs.emplace(realisation.id, realisation);
         }
 
         runPostBuildHook(