Merge branch 'fixLockFile' of https://github.com/CSVdB/nix into flakes

src/libexpr/primops/flake.cc

@@ -50,8 +50,7 @@ LockFile::FlakeEntry readFlakeEntry(nlohmann::json json)
     if (!flakeRef.isImmutable())
         throw Error("cannot use mutable flake '%s' in pure mode", flakeRef);
 
-    Hash hash = Hash((std::string) json["contentHash"]);
+    LockFile::FlakeEntry entry(flakeRef, Hash((std::string) json["contentHash"]));
-    LockFile::FlakeEntry entry(flakeRef, hash);
 
     auto nonFlakeRequires = json["nonFlakeRequires"];
 
@@ -59,9 +58,8 @@ LockFile::FlakeEntry readFlakeEntry(nlohmann::json json)
         FlakeRef flakeRef(i->value("uri", ""));
         if (!flakeRef.isImmutable())
             throw Error("requested to fetch FlakeRef '%s' purely, which is mutable", flakeRef);
-        Hash hash = Hash((std::string) i->value("contentHash", ""));
+        LockFile::NonFlakeEntry nonEntry(flakeRef, Hash(i->value("contentHash", "")));
-        LockFile::NonFlakeEntry newEntry(flakeRef, hash);
+        entry.nonFlakeEntries.insert_or_assign(i.key(), nonEntry);
-        entry.nonFlakeEntries.insert_or_assign(i.key(), newEntry);
     }
 
     auto requires = json["requires"];
@@ -89,10 +87,10 @@ LockFile readLockFile(const Path & path)
 
     for (auto i = nonFlakeRequires.begin(); i != nonFlakeRequires.end(); ++i) {
         FlakeRef flakeRef(i->value("uri", ""));
-        LockFile::NonFlakeEntry entry(flakeRef, Hash((std::string) json["contentHash"]));
+        LockFile::NonFlakeEntry nonEntry(flakeRef, Hash(i->value("contentHash", "")));
         if (!flakeRef.isImmutable())
-            throw Error("requested to fetch FlakeRef '%s' purely, which is mutable", flakeRef);
+            throw Error("found mutable FlakeRef '%s' in lockfile at path %s", flakeRef, path);
-        lockFile.nonFlakeEntries.insert_or_assign(i.key(), entry);
+        lockFile.nonFlakeEntries.insert_or_assign(i.key(), nonEntry);
     }
 
     auto requires = json["requires"];
@@ -289,8 +287,6 @@ Flake getFlake(EvalState & state, const FlakeRef & flakeRef, bool impureIsAllowe
 
     FlakeRef resolvedRef = sourceInfo.resolvedRef;
 
-    resolvedRef = sourceInfo.resolvedRef; // `resolvedRef` is now immutable
-
     state.store->assertStorePath(sourceInfo.storePath);
 
     if (state.allowedPaths)
@@ -368,73 +364,135 @@ NonFlake getNonFlake(EvalState & state, const FlakeRef & flakeRef, FlakeAlias al
     return nonFlake;
 }
 
-/* Given a flake reference, recursively fetch it and its
+LockFile entryToLockFile(const LockFile::FlakeEntry & entry)
-   dependencies.
-   FIXME: this should return a graph of flakes.
-*/
-ResolvedFlake resolveFlake(EvalState & state, const FlakeRef & topRef,
-    RegistryAccess registryAccess, bool isTopFlake)
 {
-    bool allowRegistries = registryAccess == AllowRegistry || (registryAccess == AllowRegistryAtTop && isTopFlake);
-    Flake flake = getFlake(state, topRef, allowRegistries);
-    LockFile lockFile;
-
-    if (isTopFlake)
-        lockFile = readLockFile(flake.storePath + flake.resolvedRef.subdir + "/flake.lock"); // FIXME: symlink attack
-
-    ResolvedFlake deps(flake);
-
-    for (auto & nonFlakeInfo : flake.nonFlakeRequires)
-        deps.nonFlakeDeps.push_back(getNonFlake(state, nonFlakeInfo.second, nonFlakeInfo.first));
-
-    for (auto newFlakeRef : flake.requires) {
-        auto i = lockFile.flakeEntries.find(newFlakeRef);
-        if (i != lockFile.flakeEntries.end()) newFlakeRef = i->second.ref;
-        // FIXME: propagate lockFile downwards
-        deps.flakeDeps.push_back(resolveFlake(state, newFlakeRef, registryAccess, false));
-    }
-
-    return deps;
-}
-
-LockFile::FlakeEntry dependenciesToFlakeEntry(const ResolvedFlake & resolvedFlake)
-{
-    LockFile::FlakeEntry entry(resolvedFlake.flake.resolvedRef, resolvedFlake.flake.hash);
-
-    for (auto & newResFlake : resolvedFlake.flakeDeps)
-        entry.flakeEntries.insert_or_assign(newResFlake.flake.originalRef, dependenciesToFlakeEntry(newResFlake));
-
-    for (auto & nonFlake : resolvedFlake.nonFlakeDeps)
-        entry.nonFlakeEntries.insert_or_assign(nonFlake.alias, LockFile::NonFlakeEntry(nonFlake.resolvedRef, nonFlake.hash));
-
-    return entry;
-}
-
-static LockFile makeLockFile(EvalState & evalState, FlakeRef & flakeRef)
-{
-    ResolvedFlake resFlake = resolveFlake(evalState, flakeRef, AllowRegistry);
-    LockFile::FlakeEntry entry = dependenciesToFlakeEntry(resFlake);
     LockFile lockFile;
     lockFile.flakeEntries = entry.flakeEntries;
     lockFile.nonFlakeEntries = entry.nonFlakeEntries;
     return lockFile;
 }
 
-void updateLockFile(EvalState & state, const FlakeUri & flakeUri)
+LockFile::FlakeEntry dependenciesToFlakeEntry(const ResolvedFlake & resolvedFlake)
 {
-    // FIXME: We are writing the lockfile to the store here! Very bad practice!
+    LockFile::FlakeEntry entry(resolvedFlake.flake.resolvedRef, resolvedFlake.flake.hash);
-    FlakeRef flakeRef = FlakeRef(flakeUri);
-    if (auto refData = std::get_if<FlakeRef::IsPath>(&flakeRef.data)) {
-        auto lockFile = makeLockFile(state, flakeRef);
-        writeLockFile(lockFile, refData->path + "/" + flakeRef.subdir + "/flake.lock");
 
-        // Hack: Make sure that flake.lock is visible to Git. Otherwise,
+    for (auto & info : resolvedFlake.flakeDeps)
-        // exportGit will fail to copy it to the Nix store.
+        entry.flakeEntries.insert_or_assign(info.first.to_string(), dependenciesToFlakeEntry(info.second));
-        runProgram("git", true,
+
-            { "-C", refData->path, "add", "--intent-to-add",
+    for (auto & nonFlake : resolvedFlake.nonFlakeDeps) {
-              (flakeRef.subdir == "" ? "" : flakeRef.subdir + "/") + "flake.lock" });
+        LockFile::NonFlakeEntry nonEntry(nonFlake.resolvedRef, nonFlake.hash);
-    } else
+        entry.nonFlakeEntries.insert_or_assign(nonFlake.alias, nonEntry);
-        throw Error("flakeUri %s can't be updated because it is not a path", flakeUri);
+    }
+
+    return entry;
+}
+
+bool allowedToWrite (HandleLockFile handle)
+{
+    if (handle == AllPure) return false;
+    else if (handle == TopRefUsesRegistries) return false;
+    else if (handle == UpdateLockFile) return true;
+    else if (handle == UseUpdatedLockFile) return false;
+    else if (handle == RecreateLockFile) return true;
+    else if (handle == UseNewLockFile) return false;
+    else assert(false);
+}
+
+bool recreateLockFile (HandleLockFile handle)
+{
+    if (handle == AllPure) return false;
+    else if (handle == TopRefUsesRegistries) return false;
+    else if (handle == UpdateLockFile) return false;
+    else if (handle == UseUpdatedLockFile) return false;
+    else if (handle == RecreateLockFile) return true;
+    else if (handle == UseNewLockFile) return true;
+    else assert(false);
+}
+
+bool allowedToUseRegistries (HandleLockFile handle, bool isTopRef)
+{
+    if (handle == AllPure) return false;
+    else if (handle == TopRefUsesRegistries) return isTopRef;
+    else if (handle == UpdateLockFile) return true;
+    else if (handle == UseUpdatedLockFile) return true;
+    else if (handle == RecreateLockFile) return true;
+    else if (handle == UseNewLockFile) return true;
+    else assert(false);
+}
+
+ResolvedFlake resolveFlakeFromLockFile(EvalState & state, const FlakeRef & flakeRef,
+    HandleLockFile handleLockFile, LockFile lockFile = {}, bool topRef = false)
+{
+    Flake flake = getFlake(state, flakeRef, allowedToUseRegistries(handleLockFile, topRef));
+
+    ResolvedFlake deps(flake);
+
+    for (auto & nonFlakeInfo : flake.nonFlakeRequires) {
+        FlakeRef ref = nonFlakeInfo.second;
+        auto i = lockFile.nonFlakeEntries.find(nonFlakeInfo.first);
+        if (i != lockFile.nonFlakeEntries.end()) {
+            NonFlake nonFlake = getNonFlake(state, i->second.ref, nonFlakeInfo.first);
+            if (nonFlake.hash != i->second.contentHash)
+                throw Error("the content hash of flakeref %s doesn't match", i->second.ref.to_string());
+            deps.nonFlakeDeps.push_back(nonFlake);
+        } else {
+            if (handleLockFile == AllPure || handleLockFile == TopRefUsesRegistries)
+                throw Error("the lockfile requires updating nonflake dependency %s in AllPure mode", nonFlakeInfo.first);
+            deps.nonFlakeDeps.push_back(getNonFlake(state, nonFlakeInfo.second, nonFlakeInfo.first));
+        }
+    }
+
+    for (auto newFlakeRef : flake.requires) {
+        auto i = lockFile.flakeEntries.find(newFlakeRef);
+        if (i != lockFile.flakeEntries.end()) { // Propagate lockFile downwards if possible
+            ResolvedFlake newResFlake = resolveFlakeFromLockFile(state, i->second.ref, handleLockFile, entryToLockFile(i->second));
+            if (newResFlake.flake.hash != i->second.contentHash)
+                throw Error("the content hash of flakeref %s doesn't match", i->second.ref.to_string());
+            deps.flakeDeps.insert_or_assign(newFlakeRef, newResFlake);
+        } else {
+            if (handleLockFile == AllPure || handleLockFile == TopRefUsesRegistries)
+                throw Error("the lockfile requires updating flake dependency %s in AllPure mode", newFlakeRef.to_string());
+            deps.flakeDeps.insert_or_assign(newFlakeRef, resolveFlakeFromLockFile(state, newFlakeRef, handleLockFile));
+        }
+    }
+
+    return deps;
+}
+
+/* Given a flake reference, recursively fetch it and its dependencies.
+   FIXME: this should return a graph of flakes.
+*/
+ResolvedFlake resolveFlake(EvalState & state, const FlakeRef & topRef, HandleLockFile handleLockFile)
+{
+    Flake flake = getFlake(state, topRef, allowedToUseRegistries(handleLockFile, true));
+    LockFile lockFile;
+
+    if (!recreateLockFile (handleLockFile)) {
+        // If recreateLockFile, start with an empty lockfile
+        lockFile = readLockFile(flake.storePath + "/flake.lock"); // FIXME: symlink attack
+    }
+
+    ResolvedFlake resFlake = resolveFlakeFromLockFile(state, topRef, handleLockFile, lockFile, true);
+    lockFile = entryToLockFile(dependenciesToFlakeEntry(resFlake));
+
+    if (allowedToWrite(handleLockFile)) {
+        if (auto refData = std::get_if<FlakeRef::IsPath>(&topRef.data)) {
+            writeLockFile(lockFile, refData->path + (topRef.subdir == "" ? "" : "/" + topRef.subdir) + "/flake.lock");
+
+            // Hack: Make sure that flake.lock is visible to Git, so it ends up in the Nix store.
+            runProgram("git", true, { "-C", refData->path, "add",
+                      (topRef.subdir == "" ? "" : topRef.subdir + "/") + "flake.lock" });
+        } else std::cout << "Cannot write lockfile because the FlakeRef isn't of the form IsPath." << std::endl;
+    } else if (handleLockFile != AllPure && handleLockFile != TopRefUsesRegistries)
+        std::cout << "Using updating lockfile without writing it to file" << std::endl;
+
+    return resFlake;
+}
+
+void updateLockFile (EvalState & state, const FlakeUri & flakeUri, bool recreateLockFile)
+{
+    FlakeRef flakeRef(flakeUri);
+    resolveFlake(state, flakeRef, recreateLockFile ? RecreateLockFile : UpdateLockFile);
 }
 
 void callFlake(EvalState & state, const ResolvedFlake & resFlake, Value & v)
@@ -444,7 +502,8 @@ void callFlake(EvalState & state, const ResolvedFlake & resFlake, Value & v)
 
     state.mkAttrs(v, resFlake.flakeDeps.size() + resFlake.nonFlakeDeps.size() + 8);
 
-    for (const ResolvedFlake newResFlake : resFlake.flakeDeps) {
+    for (auto info : resFlake.flakeDeps) {
+        const ResolvedFlake newResFlake = info.second;
         auto vFlake = state.allocAttr(v, newResFlake.flake.id);
         callFlake(state, newResFlake, *vFlake);
     }
@@ -485,16 +544,16 @@ void callFlake(EvalState & state, const ResolvedFlake & resFlake, Value & v)
 
 // Return the `provides` of the top flake, while assigning to `v` the provides
 // of the dependencies as well.
-void makeFlakeValue(EvalState & state, const FlakeRef & flakeRef, RegistryAccess registryAccess, Value & v)
+void makeFlakeValue(EvalState & state, const FlakeRef & flakeRef, HandleLockFile handle, Value & v)
 {
-    callFlake(state, resolveFlake(state, flakeRef, registryAccess), v);
+    callFlake(state, resolveFlake(state, flakeRef, handle), v);
 }
 
 // This function is exposed to be used in nix files.
 static void prim_getFlake(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     makeFlakeValue(state, state.forceStringNoCtx(*args[0], pos),
-        evalSettings.pureEval ? DisallowRegistry : AllowRegistryAtTop, v);
+        evalSettings.pureEval ? AllPure : UseUpdatedLockFile, v);
 }
 
 static RegisterPrimOp r2("getFlake", 1, prim_getFlake);

src/libexpr/primops/flake.hh

@@ -36,16 +36,23 @@ struct LockFile
     };
 
     std::map<FlakeRef, FlakeEntry> flakeEntries;
-    std::map<FlakeId, NonFlakeEntry> nonFlakeEntries;
+    std::map<FlakeAlias, NonFlakeEntry> nonFlakeEntries;
 };
 
 typedef std::vector<std::shared_ptr<FlakeRegistry>> Registries;
 
 Path getUserRegistryPath();
 
-enum RegistryAccess { DisallowRegistry, AllowRegistry, AllowRegistryAtTop };
+enum HandleLockFile
+    { AllPure // Everything is handled 100% purely
+    , TopRefUsesRegistries // The top FlakeRef uses the registries, apart from that, everything happens 100% purely
+    , UpdateLockFile // Update the existing lockfile and write it to file
+    , UseUpdatedLockFile // `UpdateLockFile` without writing to file
+    , RecreateLockFile // Recreate the lockfile from scratch and write it to file
+    , UseNewLockFile // `RecreateLockFile` without writing to file
+    };
 
-void makeFlakeValue(EvalState & state, const FlakeRef & flakeRef, RegistryAccess registryAccess, Value & v);
+void makeFlakeValue(EvalState &, const FlakeRef &, HandleLockFile, Value &);
 
 std::shared_ptr<FlakeRegistry> readRegistry(const Path &);
 
@@ -84,8 +91,8 @@ struct NonFlake
     FlakeRef originalRef;
     FlakeRef resolvedRef;
     std::optional<uint64_t> revCount;
+    Hash hash;
     Path storePath;
-    Hash hash; // content hash
     // date
     NonFlake(const FlakeRef & origRef, const SourceInfo & sourceInfo) : originalRef(origRef),
         resolvedRef(sourceInfo.resolvedRef), revCount(sourceInfo.revCount), storePath(sourceInfo.storePath) {};
@@ -98,14 +105,14 @@ Flake getFlake(EvalState &, const FlakeRef &, bool impureIsAllowed);
 struct ResolvedFlake
 {
     Flake flake;
-    std::vector<ResolvedFlake> flakeDeps; // The flake dependencies
+    std::map<FlakeRef, ResolvedFlake> flakeDeps; // The key in this map, is the originalRef as written in flake.nix
     std::vector<NonFlake> nonFlakeDeps;
     ResolvedFlake(const Flake & flake) : flake(flake) {}
 };
 
-ResolvedFlake resolveFlake(EvalState &, const FlakeRef &, RegistryAccess registryAccess, bool isTopFlake = true);
+ResolvedFlake resolveFlake(EvalState &, const FlakeRef &, HandleLockFile);
 
-void updateLockFile(EvalState &, const FlakeUri &);
+void updateLockFile(EvalState &, const FlakeUri &, bool recreateLockFile);
 
 void gitCloneFlake (std::string flakeUri, EvalState &, Registries, Path);
 }

src/nix/command.hh

@@ -76,10 +76,14 @@ struct SourceExprCommand : virtual Args, StoreCommand, MixEvalArgs
 {
     std::optional<Path> file;
 
-    bool updateLockFile = true;
-
     SourceExprCommand();
 
+    bool recreateLockFile = false;
+
+    bool saveLockFile = true;
+
+    bool noRegistries = false;
+
     ref<EvalState> getEvalState();
 
     std::vector<std::shared_ptr<Installable>> parseInstallables(

src/nix/flake.cc

@@ -114,7 +114,7 @@ struct CmdFlakeDeps : FlakeCommand, MixJSON, StoreCommand, MixEvalArgs
 
         FlakeRef flakeRef(flakeUri);
 
-        ResolvedFlake resFlake = resolveFlake(*evalState, flakeRef, AllowRegistryAtTop);
+        ResolvedFlake resFlake = resolveFlake(*evalState, flakeRef, UpdateLockFile);
 
         std::queue<ResolvedFlake> todo;
         todo.push(resFlake);
@@ -126,13 +126,13 @@ struct CmdFlakeDeps : FlakeCommand, MixJSON, StoreCommand, MixEvalArgs
             for (NonFlake & nonFlake : resFlake.nonFlakeDeps)
                 printNonFlakeInfo(nonFlake, json);
 
-            for (ResolvedFlake & newResFlake : resFlake.flakeDeps)
+            for (auto info : resFlake.flakeDeps)
-                todo.push(newResFlake);
+                todo.push(info.second);
         }
     }
 };
 
-struct CmdFlakeUpdate : StoreCommand, GitRepoCommand, MixEvalArgs
+struct CmdFlakeUpdate : StoreCommand, FlakeCommand, MixEvalArgs
 {
     std::string name() override
     {
@@ -148,8 +148,8 @@ struct CmdFlakeUpdate : StoreCommand, GitRepoCommand, MixEvalArgs
     {
         auto evalState = std::make_shared<EvalState>(searchPath, store);
 
-        if (gitPath == "") gitPath = absPath(".");
+        bool recreateLockFile = true;
-        updateLockFile(*evalState, gitPath);
+        updateLockFile(*evalState, flakeUri, recreateLockFile);
     }
 };
 

src/nix/installables.cc

@@ -23,9 +23,19 @@ SourceExprCommand::SourceExprCommand()
         .dest(&file);
 
     mkFlag()
-        .longName("no-update")
+        .longName("recreate-lock-file")
-        .description("don't create/update flake lock files")
+        .description("recreate lock file from scratch")
-        .set(&updateLockFile, false);
+        .set(&recreateLockFile, true);
+
+    mkFlag()
+        .longName("dont-save-lock-file")
+        .description("save the newly generated lock file")
+        .set(&saveLockFile, false);
+
+    mkFlag()
+        .longName("no-registries")
+        .description("don't use flake registries")
+        .set(&noRegistries, true);
 }
 
 ref<EvalState> SourceExprCommand::getEvalState()
@@ -157,13 +167,13 @@ struct InstallableFlake : InstallableValue
 
     Value * toValue(EvalState & state) override
     {
-        auto path = std::get_if<FlakeRef::IsPath>(&flakeRef.data);
-        if (cmd.updateLockFile && path) {
-            updateLockFile(state, path->path);
-        }
-
         auto vFlake = state.allocValue();
-        makeFlakeValue(state, flakeRef, AllowRegistryAtTop, *vFlake);
+
+        HandleLockFile handle = cmd.noRegistries ? AllPure :
+            cmd.recreateLockFile ?
+            (cmd.saveLockFile ? RecreateLockFile : UseNewLockFile)
+            : (cmd.saveLockFile ? UpdateLockFile : UseUpdatedLockFile);
+        makeFlakeValue(state, flakeRef, handle, *vFlake);
 
         auto vProvides = (*vFlake->attrs->get(state.symbols.create("provides")))->value;
 

tests/flakes.sh

@@ -9,11 +9,11 @@ clearStore
 
 registry=$TEST_ROOT/registry.json
 
-flake1=$TEST_ROOT/flake1
+flake1Dir=$TEST_ROOT/flake1
-flake2=$TEST_ROOT/flake2
+flake2Dir=$TEST_ROOT/flake2
-flake3=$TEST_ROOT/flake3
+flake3Dir=$TEST_ROOT/flake3
 
-for repo in $flake1 $flake2 $flake3; do
+for repo in $flake1Dir $flake2Dir $flake3Dir; do
     rm -rf $repo
     mkdir $repo
     git -C $repo init
@@ -21,7 +21,7 @@ for repo in $flake1 $flake2 $flake3; do
     git -C $repo config user.name "Foobar"
 done
 
-cat > $flake1/flake.nix <<EOF
+cat > $flake1Dir/flake.nix <<EOF
 {
   name = "flake1";
 
@@ -36,11 +36,11 @@ cat > $flake1/flake.nix <<EOF
 }
 EOF
 
-cp ./simple.nix ./simple.builder.sh ./config.nix $flake1/
+cp ./simple.nix ./simple.builder.sh ./config.nix $flake1Dir/
-git -C $flake1 add flake.nix simple.nix simple.builder.sh config.nix
+git -C $flake1Dir add flake.nix simple.nix simple.builder.sh config.nix
-git -C $flake1 commit -m 'Initial'
+git -C $flake1Dir commit -m 'Initial'
 
-cat > $flake2/flake.nix <<EOF
+cat > $flake2Dir/flake.nix <<EOF
 {
   name = "flake2";
 
@@ -56,10 +56,10 @@ cat > $flake2/flake.nix <<EOF
 }
 EOF
 
-git -C $flake2 add flake.nix
+git -C $flake2Dir add flake.nix
-git -C $flake2 commit -m 'Initial'
+git -C $flake2Dir commit -m 'Initial'
 
-cat > $flake3/flake.nix <<EOF
+cat > $flake3Dir/flake.nix <<EOF
 {
   name = "flake3";
 
@@ -75,20 +75,20 @@ cat > $flake3/flake.nix <<EOF
 }
 EOF
 
-git -C $flake3 add flake.nix
+git -C $flake3Dir add flake.nix
-git -C $flake3 commit -m 'Initial'
+git -C $flake3Dir commit -m 'Initial'
 
 cat > $registry <<EOF
 {
     "flakes": {
         "flake1": {
-            "uri": "file://$flake1"
+            "uri": "file://$flake1Dir"
         },
         "flake2": {
-            "uri": "file://$flake2"
+            "uri": "file://$flake2Dir"
         },
         "flake3": {
-            "uri": "file://$flake3"
+            "uri": "file://$flake3Dir"
         },
         "nixpkgs": {
             "uri": "flake1"
@@ -118,26 +118,54 @@ nix build -o $TEST_ROOT/result --flake-registry $registry flake1:
 [[ -e $TEST_ROOT/result/hello ]]
 
 # Building a flake with an unlocked dependency should fail in pure mode.
-(! nix build -o $TEST_ROOT/result --flake-registry $registry flake2:bar)
+(! nix eval "(builtins.getFlake "$flake2Dir")")
 
 # But should succeed in impure mode.
-# FIXME: this currently fails.
+nix build -o $TEST_ROOT/result --flake-registry $registry flake2:bar --impure
-#nix build -o $TEST_ROOT/result --flake-registry $registry flake2:bar --impure
 
 # Test automatic lock file generation.
-nix build -o $TEST_ROOT/result --flake-registry $registry $flake2:bar
+nix build -o $TEST_ROOT/result --flake-registry $registry $flake2Dir:bar
-[[ -e $flake2/flake.lock ]]
+[[ -e $flake2Dir/flake.lock ]]
-git -C $flake2 commit flake.lock -m 'Add flake.lock'
+git -C $flake2Dir commit flake.lock -m 'Add flake.lock'
 
 # Rerunning the build should not change the lockfile.
-#nix build -o $TEST_ROOT/result --flake-registry $registry $flake2:bar
+nix build -o $TEST_ROOT/result --flake-registry $registry $flake2Dir:bar
-#[[ -z $(git -C $flake2 diff) ]]
+[[ -z $(git -C $flake2Dir diff master) ]]
 
 # Now we should be able to build the flake in pure mode.
 nix build -o $TEST_ROOT/result --flake-registry $registry flake2:bar
 
 # Or without a registry.
-nix build -o $TEST_ROOT/result file://$flake2:bar
+nix build -o $TEST_ROOT/result file://$flake2Dir:bar
 
 # Test whether indirect dependencies work.
-#nix build -o $TEST_ROOT/result --flake-registry $registry $flake3:xyzzy
+nix build -o $TEST_ROOT/result --flake-registry $registry $flake3Dir:xyzzy
+
+# Add dependency to flake3
+rm $flake3Dir/flake.nix
+
+cat > $flake3Dir/flake.nix <<EOF
+{
+  name = "flake3";
+
+  epoch = 2019;
+
+  requires = [ "flake1" "flake2" ];
+
+  description = "Fnord";
+
+  provides = deps: rec {
+    packages.xyzzy = deps.flake2.provides.packages.bar;
+    packages.sth = deps.flake1.provides.packages.foo;
+  };
+}
+EOF
+
+git -C $flake3Dir add flake.nix
+git -C $flake3Dir commit -m 'Update flake.nix'
+
+# Check whether `nix build` works with an incomplete lockfile
+nix build -o $TEST_ROOT/result --flake-registry $registry $flake3Dir:sth
+
+# Check whether it saved the lockfile
+[[ ! (-z $(git -C $flake3Dir diff master)) ]]