Merge branch 'path-info' into ca-drv-exotic

21 files changed, 106 insertions, 99 deletions

diff --git a/src/libcmd/command.cc b/src/libcmd/command.cc
index 0d61e12d0..fd3edfc46 100644
--- a/src/libcmd/command.cc
+++ b/src/libcmd/command.cc
@@ -203,10 +203,10 @@ void MixProfile::updateProfile(const BuiltPaths & buildables)
 
     for (auto & buildable : buildables) {
         std::visit(overloaded {
-            [&](BuiltPath::Opaque bo) {
+            [&](const BuiltPath::Opaque & bo) {
                 result.push_back(bo.path);
             },
-            [&](BuiltPath::Built bfd) {
+            [&](const BuiltPath::Built & bfd) {
                 for (auto & output : bfd.outputs) {
                     result.push_back(output.second);
                 }
diff --git a/src/libcmd/installables.cc b/src/libcmd/installables.cc
index 8015cff4d..0f0fcf39e 100644
--- a/src/libcmd/installables.cc
+++ b/src/libcmd/installables.cc
@@ -697,13 +697,13 @@ std::shared_ptr<Installable> SourceExprCommand::parseInstallable(
 BuiltPaths getBuiltPaths(ref<Store> evalStore, ref<Store> store, const DerivedPaths & hopefullyBuiltPaths)
 {
     BuiltPaths res;
-    for (auto & b : hopefullyBuiltPaths)
+    for (const auto & b : hopefullyBuiltPaths)
         std::visit(
             overloaded{
-                [&](DerivedPath::Opaque bo) {
+                [&](const DerivedPath::Opaque & bo) {
                     res.push_back(BuiltPath::Opaque{bo.path});
                 },
-                [&](DerivedPath::Built bfd) {
+                [&](const DerivedPath::Built & bfd) {
                     OutputPathMap outputs;
                     auto drv = evalStore->readDerivation(bfd.drvPath);
                     auto outputHashes = staticOutputHashes(*evalStore, drv); // FIXME: expensive
@@ -823,10 +823,10 @@ StorePathSet toDerivations(
 {
     StorePathSet drvPaths;
 
-    for (auto & i : installables)
-        for (auto & b : i->toDerivedPaths())
+    for (const auto & i : installables)
+        for (const auto & b : i->toDerivedPaths())
             std::visit(overloaded {
-                [&](DerivedPath::Opaque bo) {
+                [&](const DerivedPath::Opaque & bo) {
                     if (!useDeriver)
                         throw Error("argument '%s' did not evaluate to a derivation", i->what());
                     auto derivers = store->queryValidDerivers(bo.path);
@@ -835,7 +835,7 @@ StorePathSet toDerivations(
                     // FIXME: use all derivers?
                     drvPaths.insert(*derivers.begin());
                 },
-                [&](DerivedPath::Built bfd) {
+                [&](const DerivedPath::Built & bfd) {
                     drvPaths.insert(bfd.drvPath);
                 },
             }, b.raw());
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index fd7a34926..25b9c32b2 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -1178,7 +1178,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
         // hash per output.
         auto hashModulo = hashDerivationModulo(*state.store, Derivation(drv), true);
         std::visit(overloaded {
-            [&](Hash h) {
+            [&](Hash & h) {
                 for (auto & i : outputs) {
                     auto outPath = state.store->makeOutputPath(i, h, drvName);
                     drv.env[i] = state.store->printStorePath(outPath);
@@ -1190,11 +1190,11 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
                         });
                 }
             },
-            [&](CaOutputHashes) {
+            [&](CaOutputHashes &) {
                 // Shouldn't happen as the toplevel derivation is not CA.
                 assert(false);
             },
-            [&](DeferredHash _) {
+            [&](DeferredHash &) {
                 for (auto & i : outputs) {
                     drv.outputs.insert_or_assign(i,
                         DerivationOutput {
diff --git a/src/libstore/build/entry-points.cc b/src/libstore/build/entry-points.cc
index 96deb81d1..2b77e4354 100644
--- a/src/libstore/build/entry-points.cc
+++ b/src/libstore/build/entry-points.cc
@@ -11,12 +11,12 @@ void Store::buildPaths(const std::vector<DerivedPath> & reqs, BuildMode buildMod
     Worker worker(*this, evalStore ? *evalStore : *this);
 
     Goals goals;
-    for (auto & br : reqs) {
+    for (const auto & br : reqs) {
         std::visit(overloaded {
-            [&](DerivedPath::Built bfd) {
+            [&](const DerivedPath::Built & bfd) {
                 goals.insert(worker.makeDerivationGoal(bfd.drvPath, bfd.outputs, buildMode));
             },
-            [&](DerivedPath::Opaque bo) {
+            [&](const DerivedPath::Opaque & bo) {
                 goals.insert(worker.makePathSubstitutionGoal(bo.path, buildMode == bmRepair ? Repair : NoRepair));
             },
         }, br.raw());
diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 3dd3a48b7..f574e64cf 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -1094,10 +1094,10 @@ void LocalDerivationGoal::writeStructuredAttrs()
 static StorePath pathPartOfReq(const DerivedPath & req)
 {
     return std::visit(overloaded {
-        [&](DerivedPath::Opaque bo) {
+        [&](const DerivedPath::Opaque & bo) {
             return bo.path;
         },
-        [&](DerivedPath::Built bfd)  {
+        [&](const DerivedPath::Built & bfd)  {
             return bfd.drvPath;
         },
     }, req.raw());
@@ -2155,8 +2155,8 @@ void LocalDerivationGoal::registerOutputs()
                 /* Since we'll use the already installed versions of these, we
                    can treat them as leaves and ignore any references they
                    have. */
-                [&](AlreadyRegistered _) { return StringSet {}; },
-                [&](PerhapsNeedToRegister refs) {
+                [&](const AlreadyRegistered &) { return StringSet {}; },
+                [&](const PerhapsNeedToRegister & refs) {
                     StringSet referencedOutputs;
                     /* FIXME build inverted map up front so no quadratic waste here */
                     for (auto & r : refs.refs)
@@ -2192,11 +2192,11 @@ void LocalDerivationGoal::registerOutputs()
         };
 
         std::optional<StorePathSet> referencesOpt = std::visit(overloaded {
-            [&](AlreadyRegistered skippedFinalPath) -> std::optional<StorePathSet> {
+            [&](const AlreadyRegistered & skippedFinalPath) -> std::optional<StorePathSet> {
                 finish(skippedFinalPath.path);
                 return std::nullopt;
             },
-            [&](PerhapsNeedToRegister r) -> std::optional<StorePathSet> {
+            [&](const PerhapsNeedToRegister & r) -> std::optional<StorePathSet> {
                 return r.refs;
             },
         }, outputReferencesIfUnregistered.at(outputName));
@@ -2262,10 +2262,10 @@ void LocalDerivationGoal::registerOutputs()
             std::string oldHashPart { scratchPath.hashPart() };
             HashModuloSink caSink { outputHash.hashType, oldHashPart };
             std::visit(overloaded {
-                [&](TextHashMethod _) {
+                [&](const TextHashMethod &) {
                     readFile(actualPath, caSink);
                 },
-                [&](FileIngestionMethod m2) {
+                [&](const FileIngestionMethod & m2) {
                     switch (m2) {
                     case FileIngestionMethod::Recursive:
                         dumpPath(actualPath, caSink);
@@ -2312,7 +2312,7 @@ void LocalDerivationGoal::registerOutputs()
         };
 
         ValidPathInfo newInfo = std::visit(overloaded {
-            [&](DerivationOutputInputAddressed output) {
+            [&](const DerivationOutputInputAddressed & output) {
                 /* input-addressed case */
                 auto requiredFinalPath = output.path;
                 /* Preemptively add rewrite rule for final hash, as that is
@@ -2328,7 +2328,7 @@ void LocalDerivationGoal::registerOutputs()
                 static_cast<PathReferences<StorePath> &>(newInfo0) = rewriteRefs();
                 return newInfo0;
             },
-            [&](DerivationOutputCAFixed dof) {
+            [&](const DerivationOutputCAFixed & dof) {
                 auto wanted = getContentAddressHash(dof.ca);
 
                 auto newInfo0 = newInfoFromCA(DerivationOutputCAFloating {
diff --git a/src/libstore/content-address.cc b/src/libstore/content-address.cc
index 6a695fe68..e8c6b94be 100644
--- a/src/libstore/content-address.cc
+++ b/src/libstore/content-address.cc
@@ -23,7 +23,7 @@ std::string makeFileIngestionPrefix(FileIngestionMethod m)
 
 std::string makeContentAddressingPrefix(ContentAddressMethod m) {
     return std::visit(overloaded {
-        [](TextHashMethod _) -> std::string { return "text:"; },
+        [](TextHashMethod) -> std::string { return "text:"; },
         [](FileIngestionMethod m2) {
              /* Not prefixed for back compat with things that couldn't produce text before. */
             return makeFileIngestionPrefix(m2);
@@ -52,11 +52,11 @@ std::string makeFixedOutputCA(FileIngestionMethod method, const Hash & hash)
 std::string renderContentAddress(ContentAddress ca)
 {
     return std::visit(overloaded {
-        [](TextHash th) {
+        [](TextHash & th) {
             return "text:"
                 + th.hash.to_string(Base32, true);
         },
-        [](FixedOutputHash fsh) {
+        [](FixedOutputHash & fsh) {
             return "fixed:"
                 + makeFileIngestionPrefix(fsh.method)
                 + fsh.hash.to_string(Base32, true);
@@ -128,12 +128,12 @@ ContentAddress parseContentAddress(std::string_view rawCa) {
     auto hashType = hashType_; // work around clang bug
 
     return std::visit(overloaded {
-        [&](TextHashMethod _) {
+        [&](TextHashMethod &) {
             return ContentAddress(TextHash {
                 .hash = Hash::parseNonSRIUnprefixed(rest, hashType)
             });
         },
-        [&](FileIngestionMethod fim) {
+        [&](FileIngestionMethod & fim) {
             return ContentAddress(FixedOutputHash {
                 .method = fim,
                 .hash = Hash::parseNonSRIUnprefixed(rest, hashType),
@@ -185,10 +185,10 @@ ContentAddressWithReferences contentAddressFromMethodHashAndRefs(
 ContentAddressMethod getContentAddressMethod(const ContentAddressWithReferences & ca)
 {
     return std::visit(overloaded {
-        [](TextInfo th) -> ContentAddressMethod {
+        [](const TextInfo & th) -> ContentAddressMethod {
             return TextHashMethod {};
         },
-        [](FixedOutputInfo fsh) -> ContentAddressMethod {
+        [](const FixedOutputInfo & fsh) -> ContentAddressMethod {
             return fsh.method;
         },
     }, ca);
@@ -197,10 +197,10 @@ ContentAddressMethod getContentAddressMethod(const ContentAddressWithReferences
 Hash getContentAddressHash(const ContentAddress & ca)
 {
     return std::visit(overloaded {
-        [](TextHash th) {
+        [](const TextHash & th) {
             return th.hash;
         },
-        [](FixedOutputHash fsh) {
+        [](const FixedOutputHash & fsh) {
             return fsh.hash;
         },
     }, ca);
@@ -208,10 +208,10 @@ Hash getContentAddressHash(const ContentAddress & ca)
 
 ContentAddressWithReferences caWithoutRefs(const ContentAddress & ca) {
     return std::visit(overloaded {
-        [&](TextHash h) -> ContentAddressWithReferences {
+        [&](const TextHash & h) -> ContentAddressWithReferences {
             return TextInfo { h, {}};
         },
-        [&](FixedOutputHash h) -> ContentAddressWithReferences {
+        [&](const FixedOutputHash & h) -> ContentAddressWithReferences {
             return FixedOutputInfo { h, {}};
         },
     }, ca);
@@ -220,10 +220,10 @@ ContentAddressWithReferences caWithoutRefs(const ContentAddress & ca) {
 Hash getContentAddressHash(const ContentAddressWithReferences & ca)
 {
     return std::visit(overloaded {
-        [](TextInfo th) {
+        [](const TextInfo & th) {
             return th.hash;
         },
-        [](FixedOutputInfo fsh) {
+        [](const FixedOutputInfo & fsh) {
             return fsh.hash;
         },
     }, ca);
diff --git a/src/libstore/daemon.cc b/src/libstore/daemon.cc
index 2b8772a8d..74dd11cbd 100644
--- a/src/libstore/daemon.cc
+++ b/src/libstore/daemon.cc
@@ -396,7 +396,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
                 FramedSource source(from);
                 // TODO this is essentially RemoteStore::addCAToStore. Move it up to Store.
                 return std::visit(overloaded {
-                    [&](TextHashMethod _) {
+                    [&](TextHashMethod &) {
                         if (hashType != htSHA256)
                             throw UnimplementedError("Only SHA-256 is supported for adding text-hashed data, but '%1' was given",
                                 printHashType(hashType));
@@ -405,7 +405,7 @@ static void performOp(TunnelLogger * logger, ref<Store> store,
                         auto path = store->addTextToStore(name, contents, refs, repair);
                         return store->queryPathInfo(path);
                     },
-                    [&](FileIngestionMethod fim) {
+                    [&](FileIngestionMethod & fim) {
                         if (!refs.empty())
                             throw UnimplementedError("cannot yet have refs with flat or nar-hashed data");
                         auto path = store->addToStoreFromDump(source, name, fim, hashType, repair);
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index b0aaa0f51..7868c7f94 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -11,18 +11,18 @@ namespace nix {
 std::optional<StorePath> DerivationOutput::path(const Store & store, std::string_view drvName, std::string_view outputName) const
 {
     return std::visit(overloaded {
-        [](DerivationOutputInputAddressed doi) -> std::optional<StorePath> {
+        [](const DerivationOutputInputAddressed & doi) -> std::optional<StorePath> {
             return { doi.path };
         },
-        [&](DerivationOutputCAFixed dof) -> std::optional<StorePath> {
+        [&](const DerivationOutputCAFixed & dof) -> std::optional<StorePath> {
             return {
                 dof.path(store, drvName, outputName)
             };
         },
-        [](DerivationOutputCAFloating dof) -> std::optional<StorePath> {
+        [](const DerivationOutputCAFloating & dof) -> std::optional<StorePath> {
             return std::nullopt;
         },
-        [](DerivationOutputDeferred) -> std::optional<StorePath> {
+        [](const DerivationOutputDeferred &) -> std::optional<StorePath> {
             return std::nullopt;
         },
     }, output);
@@ -330,22 +330,22 @@ string Derivation::unparse(const Store & store, bool maskOutputs,
         if (first) first = false; else s += ',';
         s += '('; printUnquotedString(s, i.first);
         std::visit(overloaded {
-            [&](DerivationOutputInputAddressed doi) {
+            [&](const DerivationOutputInputAddressed & doi) {
                 s += ','; printUnquotedString(s, maskOutputs ? "" : store.printStorePath(doi.path));
                 s += ','; printUnquotedString(s, "");
                 s += ','; printUnquotedString(s, "");
             },
-            [&](DerivationOutputCAFixed dof) {
+            [&](const DerivationOutputCAFixed & dof) {
                 s += ','; printUnquotedString(s, maskOutputs ? "" : store.printStorePath(dof.path(store, name, i.first)));
                 s += ','; printUnquotedString(s, printMethodAlgo(dof.ca));
                 s += ','; printUnquotedString(s, getContentAddressHash(dof.ca).to_string(Base16, false));
             },
-            [&](DerivationOutputCAFloating dof) {
+            [&](const DerivationOutputCAFloating & dof) {
                 s += ','; printUnquotedString(s, "");
                 s += ','; printUnquotedString(s, makeContentAddressingPrefix(dof.method) + printHashType(dof.hashType));
                 s += ','; printUnquotedString(s, "");
             },
-            [&](DerivationOutputDeferred) {
+            [&](const DerivationOutputDeferred &) {
                 s += ','; printUnquotedString(s, "");
                 s += ','; printUnquotedString(s, "");
                 s += ','; printUnquotedString(s, "");
@@ -418,13 +418,13 @@ DerivationType BasicDerivation::type() const
     std::optional<HashType> floatingHashType;
     for (auto & i : outputs) {
         std::visit(overloaded {
-            [&](DerivationOutputInputAddressed _) {
+            [&](const DerivationOutputInputAddressed &) {
                inputAddressedOutputs.insert(i.first);
             },
-            [&](DerivationOutputCAFixed _) {
+            [&](const DerivationOutputCAFixed &) {
                 fixedCAOutputs.insert(i.first);
             },
-            [&](DerivationOutputCAFloating dof) {
+            [&](const DerivationOutputCAFloating & dof) {
                 floatingCAOutputs.insert(i.first);
                 if (!floatingHashType) {
                     floatingHashType = dof.hashType;
@@ -433,7 +433,7 @@ DerivationType BasicDerivation::type() const
                         throw Error("All floating outputs must use the same hash type");
                 }
             },
-            [&](DerivationOutputDeferred _) {
+            [&](const DerivationOutputDeferred &) {
                deferredIAOutputs.insert(i.first);
             },
         }, i.second.output);
@@ -536,15 +536,15 @@ DrvHashModulo hashDerivationModulo(Store & store, const Derivation & drv, bool m
         const auto & res = pathDerivationModulo(store, i.first);
         std::visit(overloaded {
             // Regular non-CA derivation, replace derivation
-            [&](Hash drvHash) {
+            [&](const Hash & drvHash) {
                 inputs2.insert_or_assign(drvHash.to_string(Base16, false), i.second);
             },
-            [&](DeferredHash deferredHash) {
+            [&](const DeferredHash & deferredHash) {
                 isDeferred = true;
                 inputs2.insert_or_assign(deferredHash.hash.to_string(Base16, false), i.second);
             },
             // CA derivation's output hashes
-            [&](CaOutputHashes outputHashes) {
+            [&](const CaOutputHashes & outputHashes) {
                 std::set<std::string> justOut = { "out" };
                 for (auto & output : i.second) {
                     /* Put each one in with a single "out" output.. */
@@ -570,17 +570,17 @@ std::map<std::string, Hash> staticOutputHashes(Store & store, const Derivation &
 {
     std::map<std::string, Hash> res;
     std::visit(overloaded {
-        [&](Hash drvHash) {
+        [&](const Hash & drvHash) {
             for (auto & outputName : drv.outputNames()) {
                 res.insert({outputName, drvHash});
             }
         },
-        [&](DeferredHash deferredHash) {
+        [&](const DeferredHash & deferredHash) {
             for (auto & outputName : drv.outputNames()) {
                 res.insert({outputName, deferredHash.hash});
             }
         },
-        [&](CaOutputHashes outputHashes) {
+        [&](const CaOutputHashes & outputHashes) {
             res = outputHashes;
         },
     }, hashDerivationModulo(store, drv, true));
@@ -664,22 +664,22 @@ void writeDerivation(Sink & out, const Store & store, const BasicDerivation & dr
     for (auto & i : drv.outputs) {
         out << i.first;
         std::visit(overloaded {
-            [&](DerivationOutputInputAddressed doi) {
+            [&](const DerivationOutputInputAddressed & doi) {
                 out << store.printStorePath(doi.path)
                     << ""
                     << "";
             },
-            [&](DerivationOutputCAFixed dof) {
+            [&](const DerivationOutputCAFixed & dof) {
                 out << store.printStorePath(dof.path(store, drv.name, i.first))
                     << printMethodAlgo(dof.ca)
                     << getContentAddressHash(dof.ca).to_string(Base16, false);
             },
-            [&](DerivationOutputCAFloating dof) {
+            [&](const DerivationOutputCAFloating & dof) {
                 out << ""
                     << (makeContentAddressingPrefix(dof.method) + printHashType(dof.hashType))
                     << "";
             },
-            [&](DerivationOutputDeferred) {
+            [&](const DerivationOutputDeferred &) {
                 out << ""
                     << ""
                     << "";
diff --git a/src/libstore/derived-path.cc b/src/libstore/derived-path.cc
index 8da81d0ac..e55af21e9 100644
--- a/src/libstore/derived-path.cc
+++ b/src/libstore/derived-path.cc
@@ -24,8 +24,8 @@ StorePathSet BuiltPath::outPaths() const
 {
     return std::visit(
         overloaded{
-            [](BuiltPath::Opaque p) { return StorePathSet{p.path}; },
-            [](BuiltPath::Built b) {
+            [](const BuiltPath::Opaque & p) { return StorePathSet{p.path}; },
+            [](const BuiltPath::Built & b) {
                 StorePathSet res;
                 for (auto & [_, path] : b.outputs)
                     res.insert(path);
@@ -94,8 +94,8 @@ RealisedPath::Set BuiltPath::toRealisedPaths(Store & store) const
     RealisedPath::Set res;
     std::visit(
         overloaded{
-            [&](BuiltPath::Opaque p) { res.insert(p.path); },
-            [&](BuiltPath::Built p) {
+            [&](const BuiltPath::Opaque & p) { res.insert(p.path); },
+            [&](const BuiltPath::Built & p) {
                 auto drvHashes =
                     staticOutputHashes(store, store.readDerivation(p.drvPath));
                 for (auto& [outputName, outputPath] : p.outputs) {
diff --git a/src/libstore/legacy-ssh-store.cc b/src/libstore/legacy-ssh-store.cc
index 571719043..770827b85 100644
--- a/src/libstore/legacy-ssh-store.cc
+++ b/src/libstore/legacy-ssh-store.cc
@@ -247,6 +247,10 @@ private:
             conn.to
                 << settings.buildRepeat
                 << settings.enforceDeterminism;
+
+        if (GET_PROTOCOL_MINOR(conn.remoteVersion) >= 7) {
+            conn.to << ((int) settings.keepFailed);
+        }
     }
 
 public:
@@ -289,10 +293,10 @@ public:
         for (auto & p : drvPaths) {
             auto sOrDrvPath = StorePathWithOutputs::tryFromDerivedPath(p);
             std::visit(overloaded {
-                [&](StorePathWithOutputs s) {
+                [&](const StorePathWithOutputs & s) {
                     ss.push_back(s.to_string(*this));
                 },
-                [&](StorePath drvPath) {
+                [&](const StorePath & drvPath) {
                     throw Error("wanted to fetch '%s' but the legacy ssh protocol doesn't support merely substituting drv files via the build paths command. It would build them instead. Try using ssh-ng://", printStorePath(drvPath));
                 },
             }, sOrDrvPath);
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 3d6de09d3..8fcedd2fc 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -681,7 +681,7 @@ void LocalStore::checkDerivationOutputs(const StorePath & drvPath, const Derivat
     std::optional<Hash> h;
     for (auto & i : drv.outputs) {
         std::visit(overloaded {
-            [&](DerivationOutputInputAddressed doia) {
+            [&](const DerivationOutputInputAddressed & doia) {
                 if (!h) {
                     // somewhat expensive so we do lazily
                     auto temp = hashDerivationModulo(*this, drv, true);
@@ -693,14 +693,14 @@ void LocalStore::checkDerivationOutputs(const StorePath & drvPath, const Derivat
                         printStorePath(drvPath), printStorePath(doia.path), printStorePath(recomputed));
                 envHasRightPath(doia.path, i.first);
             },
-            [&](DerivationOutputCAFixed dof) {
+            [&](const DerivationOutputCAFixed & dof) {
                 auto path = dof.path(*this, drvName, i.first);
                 envHasRightPath(path, i.first);
             },
-            [&](DerivationOutputCAFloating _) {
+            [&](const DerivationOutputCAFloating &) {
                 /* Nothing to check */
             },
-            [&](DerivationOutputDeferred) {
+            [&](const DerivationOutputDeferred &) {
             },
         }, i.second.output);
     }
diff --git a/src/libstore/misc.cc b/src/libstore/misc.cc
index 44809e014..6a98934ef 100644
--- a/src/libstore/misc.cc
+++ b/src/libstore/misc.cc
@@ -88,12 +88,12 @@ std::optional<ContentAddress> getDerivationCA(const BasicDerivation & drv)
         return std::nullopt;
     if (auto dof = std::get_if<DerivationOutputCAFixed>(&out->second.output)) {
         return std::visit(overloaded {
-            [&](TextInfo ti) -> std::optional<ContentAddress> {
+            [&](const TextInfo & ti) -> std::optional<ContentAddress> {
                 if (!ti.references.empty())
                     return std::nullopt;
                 return static_cast<TextHash>(ti);
             },
-            [&](FixedOutputInfo fi) -> std::optional<ContentAddress> {
+            [&](const FixedOutputInfo & fi) -> std::optional<ContentAddress> {
                 if (fi.references != PathReferences<StorePath> {})
                     return std::nullopt;
                 return static_cast<FixedOutputHash>(fi);
@@ -177,7 +177,7 @@ void Store::queryMissing(const std::vector<DerivedPath> & targets,
         }
 
         std::visit(overloaded {
-          [&](DerivedPath::Built bfd) {
+          [&](const DerivedPath::Built & bfd) {
             if (!isValidPath(bfd.drvPath)) {
                 // FIXME: we could try to substitute the derivation.
                 auto state(state_.lock());
@@ -210,7 +210,7 @@ void Store::queryMissing(const std::vector<DerivedPath> & targets,
                 mustBuildDrv(bfd.drvPath, *drv);
 
           },
-          [&](DerivedPath::Opaque bo) {
+          [&](const DerivedPath::Opaque & bo) {
 
             if (isValidPath(bo.path)) return;
 
diff --git a/src/libstore/path-with-outputs.cc b/src/libstore/path-with-outputs.cc
index 865d64cf2..e5a121e00 100644
--- a/src/libstore/path-with-outputs.cc
+++ b/src/libstore/path-with-outputs.cc
@@ -31,14 +31,14 @@ std::vector<DerivedPath> toDerivedPaths(const std::vector<StorePathWithOutputs>
 std::variant<StorePathWithOutputs, StorePath> StorePathWithOutputs::tryFromDerivedPath(const DerivedPath & p)
 {
     return std::visit(overloaded {
-        [&](DerivedPath::Opaque bo) -> std::variant<StorePathWithOutputs, StorePath> {
+        [&](const DerivedPath::Opaque & bo) -> std::variant<StorePathWithOutputs, StorePath> {
             if (bo.path.isDerivation()) {
                 // drv path gets interpreted as "build", not "get drv file itself"
                 return bo.path;
             }
             return StorePathWithOutputs { bo.path };
         },
-        [&](DerivedPath::Built bfd) -> std::variant<StorePathWithOutputs, StorePath> {
+        [&](const DerivedPath::Built & bfd) -> std::variant<StorePathWithOutputs, StorePath> {
             return StorePathWithOutputs { bfd.drvPath, bfd.outputs };
         },
     }, p.raw());
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index 85f050c6d..0df432898 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -530,7 +530,7 @@ ref<const ValidPathInfo> RemoteStore::addCAToStore(
         if (repair) throw Error("repairing is not supported when building through the Nix daemon protocol < 1.25");
 
         std::visit(overloaded {
-            [&](TextHashMethod thm) -> void {
+            [&](const TextHashMethod & thm) -> void {
                 if (hashType != htSHA256)
                     throw UnimplementedError("Only SHA-256 is supported for adding text-hashed data, but '%1' was given",
                         printHashType(hashType));
@@ -539,7 +539,7 @@ ref<const ValidPathInfo> RemoteStore::addCAToStore(
                 worker_proto::write(*this, conn->to, references);
                 conn.processStderr();
             },
-            [&](FileIngestionMethod fim) -> void {
+            [&](const FileIngestionMethod & fim) -> void {
                 conn->to
                     << wopAddToStore
                     << name
@@ -710,10 +710,10 @@ static void writeDerivedPaths(RemoteStore & store, ConnectionHandle & conn, cons
         for (auto & p : reqs) {
             auto sOrDrvPath = StorePathWithOutputs::tryFromDerivedPath(p);
             std::visit(overloaded {
-                [&](StorePathWithOutputs s) {
+                [&](const StorePathWithOutputs & s) {
                     ss.push_back(s.to_string(store));
                 },
-                [&](StorePath drvPath) {
+                [&](const StorePath & drvPath) {
                     throw Error("trying to request '%s', but daemon protocol %d.%d is too old (< 1.29) to request a derivation file",
                         store.printStorePath(drvPath),
                         GET_PROTOCOL_MAJOR(conn->daemonVersion),
diff --git a/src/libstore/serve-protocol.hh b/src/libstore/serve-protocol.hh
index 02d0810cc..3f76baa82 100644
--- a/src/libstore/serve-protocol.hh
+++ b/src/libstore/serve-protocol.hh
@@ -5,7 +5,7 @@ namespace nix {
 #define SERVE_MAGIC_1 0x390c9deb
 #define SERVE_MAGIC_2 0x5452eecb
 
-#define SERVE_PROTOCOL_VERSION (2 << 8 | 6)
+#define SERVE_PROTOCOL_VERSION (2 << 8 | 7)
 #define GET_PROTOCOL_MAJOR(x) ((x) & 0xff00)
 #define GET_PROTOCOL_MINOR(x) ((x) & 0x00ff)
 
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 3cb3356f3..a57eab3e6 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -208,10 +208,10 @@ StorePath Store::makeFixedOutputPathFromCA(const StorePathDescriptor & desc) con
 {
     // New template
     return std::visit(overloaded {
-        [&](TextInfo ti) {
+        [&](const TextInfo & ti) {
             return makeTextPath(desc.name, ti);
         },
-        [&](FixedOutputInfo foi) {
+        [&](const FixedOutputInfo & foi) {
             return makeFixedOutputPath(desc.name, foi);
         }
     }, desc.info);
@@ -1150,13 +1150,13 @@ std::optional<StorePathDescriptor> ValidPathInfo::fullStorePathDescriptorOpt() c
     return StorePathDescriptor {
         .name = std::string { path.name() },
         .info = std::visit(overloaded {
-            [&](TextHash th) {
+            [&](const TextHash & th) {
                 TextInfo info { th };
                 assert(!hasSelfReference);
                 info.references = references;
                 return ContentAddressWithReferences { info };
             },
-            [&](FixedOutputHash foh) {
+            [&](const FixedOutputHash & foh) {
                 FixedOutputInfo info { foh };
                 info.references = static_cast<PathReferences<StorePath>>(*this);
                 return ContentAddressWithReferences { info };
@@ -1218,11 +1218,11 @@ ValidPathInfo::ValidPathInfo(
       , narHash(narHash)
 {
     std::visit(overloaded {
-        [this](TextInfo ti) {
+        [this](const TextInfo & ti) {
             this->references = ti.references;
             this->ca = TextHash { std::move(ti) };
         },
-        [this](FixedOutputInfo foi) {
+        [this](const FixedOutputInfo & foi) {
             *(static_cast<PathReferences<StorePath> *>(this)) = foi.references;
             this->ca = FixedOutputHash { (FixedOutputHash) std::move(foi) };
         },
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 7947e65fb..24a488d43 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -807,6 +807,9 @@ static void opServe(Strings opFlags, Strings opArgs)
             settings.enforceDeterminism = readInt(in);
             settings.runDiffHook = true;
         }
+        if (GET_PROTOCOL_MINOR(clientVersion) >= 7) {
+            settings.keepFailed = (bool) readInt(in);
+        }
         settings.printRepeatedBuilds = false;
     };
 
diff --git a/src/nix/build.cc b/src/nix/build.cc
index ce6df7df8..6e31757a2 100644
--- a/src/nix/build.cc
+++ b/src/nix/build.cc
@@ -66,12 +66,12 @@ struct CmdBuild : InstallablesCommand, MixDryRun, MixJSON, MixProfile
                 for (const auto & [_i, buildable] : enumerate(buildables)) {
                     auto i = _i;
                     std::visit(overloaded {
-                        [&](BuiltPath::Opaque bo) {
+                        [&](const BuiltPath::Opaque & bo) {
                             std::string symlink = outLink;
                             if (i) symlink += fmt("-%d", i);
                             store2->addPermRoot(bo.path, absPath(symlink));
                         },
-                        [&](BuiltPath::Built bfd) {
+                        [&](const BuiltPath::Built & bfd) {
                             for (auto & output : bfd.outputs) {
                                 std::string symlink = outLink;
                                 if (i) symlink += fmt("-%d", i);
diff --git a/src/nix/log.cc b/src/nix/log.cc
index 962c47525..fd3c1d787 100644
--- a/src/nix/log.cc
+++ b/src/nix/log.cc
@@ -35,10 +35,10 @@ struct CmdLog : InstallableCommand
         RunPager pager;
         for (auto & sub : subs) {
             auto log = std::visit(overloaded {
-                [&](DerivedPath::Opaque bo) {
+                [&](const DerivedPath::Opaque & bo) {
                     return sub->getBuildLog(bo.path);
                 },
-                [&](DerivedPath::Built bfd) {
+                [&](const DerivedPath::Built & bfd) {
                     return sub->getBuildLog(bfd.drvPath);
                 },
             }, b.raw());
diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index bd5042d8f..916966997 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -269,11 +269,11 @@ struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
                     ProfileElement element;
 
                     std::visit(overloaded {
-                        [&](BuiltPath::Opaque bo) {
+                        [&](const BuiltPath::Opaque & bo) {
                             pathsToBuild.push_back(bo);
                             element.storePaths.insert(bo.path);
                         },
-                        [&](BuiltPath::Built bfd) {
+                        [&](const BuiltPath::Built & bfd) {
                             // TODO: Why are we querying if we know the output
                             // names already? Is it just to figure out what the
                             // default one is?
diff --git a/src/nix/show-derivation.cc b/src/nix/show-derivation.cc
index d13960280..f07fedaf0 100644
--- a/src/nix/show-derivation.cc
+++ b/src/nix/show-derivation.cc
@@ -65,19 +65,19 @@ struct CmdShowDerivation : InstallablesCommand
                     auto & outputName = _outputName; // work around clang bug
                     auto outputObj { outputsObj.object(outputName) };
                     std::visit(overloaded {
-                        [&](DerivationOutputInputAddressed doi) {
+                        [&](const DerivationOutputInputAddressed & doi) {
                             outputObj.attr("path", store->printStorePath(doi.path));
                         },
-                        [&](DerivationOutputCAFixed dof) {
+                        [&](const DerivationOutputCAFixed & dof) {
                             outputObj.attr("path", store->printStorePath(dof.path(*store, drv.name, outputName)));
                             outputObj.attr("hashAlgo", printMethodAlgo(dof.ca));
                             outputObj.attr("hash", getContentAddressHash(dof.ca).to_string(Base16, false));
                             // FIXME print refs?
                         },
-                        [&](DerivationOutputCAFloating dof) {
+                        [&](const DerivationOutputCAFloating & dof) {
                             outputObj.attr("hashAlgo", makeContentAddressingPrefix(dof.method) + printHashType(dof.hashType));
                         },
-                        [&](DerivationOutputDeferred) {},
+                        [&](const DerivationOutputDeferred &) {},
                     }, output.output);
                 }
             }