From a4ec6cb1da63941c9ec3e7ffcb7639fc21b858c8 Mon Sep 17 00:00:00 2001
From: regnat <rg@regnat.ovh>
Date: Fri, 16 Jul 2021 11:40:56 +0200
Subject: [PATCH] Be more lenient when realisations have a conflicting
 dependency set
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- This can legitimately happen (for example because of a non-determinism
  causing a build-time dependency to be kept or not as a runtime
  reference)
- Because of older Nix versions, it can happen that we encounter a
  realisation with an (erroneously) empty set of dependencies, in which
  case we don’t want to fail, but just warn the user and try to fix it.
---
 src/libstore/local-store.cc |  8 ++++----
 src/libstore/realisation.cc | 12 ++++++++++--
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index d7c7f8e1d..747eb205e 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -342,7 +342,7 @@ LocalStore::LocalStore(const Params & params)
     if (settings.isExperimentalFeatureEnabled("ca-derivations")) {
         state->stmts->RegisterRealisedOutput.create(state->db,
             R"(
-                insert or replace into Realisations (drvPath, outputName, outputPath, signatures)
+                insert into Realisations (drvPath, outputName, outputPath, signatures)
                 values (?, ?, (select id from ValidPaths where path = ?), ?)
                 ;
             )");
@@ -379,7 +379,7 @@ LocalStore::LocalStore(const Params & params)
             R"(
                 insert or replace into RealisationsRefs (referrer, realisationReference)
                 values (
-                    ?,
+                    (select id from Realisations where drvPath = ? and outputName = ?),
                     (select id from Realisations where drvPath = ? and outputName = ?));
             )");
     }
@@ -748,7 +748,6 @@ void LocalStore::registerDrvOutput(const Realisation & info)
                 (concatStringsSep(" ", info.signatures))
                 .exec();
         }
-        uint64_t myId = state->db.getLastInsertedRowId();
         for (auto & [outputId, depPath] : info.dependentRealisations) {
             auto localRealisation = queryRealisationCore_(*state, outputId);
             if (!localRealisation)
@@ -761,7 +760,8 @@ void LocalStore::registerDrvOutput(const Realisation & info)
                             "match what we have locally",
                     info.id.to_string(), outputId.to_string());
             state->stmts->AddRealisationReference.use()
-                (myId)
+                (info.id.strHash())
+                (info.id.outputName)
                 (outputId.strHash())
                 (outputId.outputName)
                 .exec();
diff --git a/src/libstore/realisation.cc b/src/libstore/realisation.cc
index eadec594c..f871e6437 100644
--- a/src/libstore/realisation.cc
+++ b/src/libstore/realisation.cc
@@ -144,8 +144,16 @@ bool Realisation::isCompatibleWith(const Realisation & other) const
 {
     assert (id == other.id);
     if (outPath == other.outPath) {
-        assert(dependentRealisations == other.dependentRealisations);
-        return true;
+        if (dependentRealisations.empty() != other.dependentRealisations.empty()) {
+            warn(
+                "Encountered a realisation for '%s' with an empty set of "
+                "dependencies. This is likely an artifact from an older Nix. "
+                "I’ll try to fix the realisation if I can",
+                id.to_string());
+            return true;
+        } else if (dependentRealisations == other.dependentRealisations) {
+            return true;
+        }
     }
     return false;
 }