Merge remote-tracking branch 'upstream/master' into list-experimental-features

.github/PULL_REQUEST_TEMPLATE.md

@@ -23,6 +23,7 @@ Maintainers: tick if completed or explain if not relevant
    - unit tests - `src/*/tests`
    - integration tests - `tests/nixos/*`
  - [ ] documentation in the manual
+ - [ ] documentation in the internal API docs
  - [ ] code and comments are self-explanatory
  - [ ] commit message explains why the change was made
  - [ ] new feature or incompatible change: updated release notes

local.mk

@@ -1,6 +1,8 @@
 clean-files += Makefile.config
 
-GLOBAL_CXXFLAGS += -Wno-deprecated-declarations
+GLOBAL_CXXFLAGS += -Wno-deprecated-declarations -Werror=switch
+# Allow switch-enum to be overridden for files that do not support it, usually because of dependency headers.
+ERROR_SWITCH_ENUM = -Werror=switch-enum
 
 $(foreach i, config.h $(wildcard src/lib*/*.hh), \
   $(eval $(call install-file-in, $(i), $(includedir)/nix, 0644)))

maintainers/README.md

@@ -69,6 +69,7 @@ Issues on the board progress through the following states:
   2. [security](https://github.com/NixOS/nix/labels/security)
   3. [regression](https://github.com/NixOS/nix/labels/regression)
   4. [bug](https://github.com/NixOS/nix/issues?q=is%3Aopen+label%3Abug+sort%3Areactions-%2B1-desc)
+  5. [tests of existing functionality](https://github.com/NixOS/nix/issues?q=is%3Aopen+label%3Atests+-label%3Afeature+sort%3Areactions-%2B1-desc)
 
   - [oldest pull requests](https://github.com/NixOS/nix/pulls?q=is%3Apr+is%3Aopen+sort%3Acreated-asc)
   - [most popular pull requests](https://github.com/NixOS/nix/pulls?q=is%3Apr+is%3Aopen+sort%3Areactions-%2B1-desc)
@@ -91,7 +92,7 @@ Issues on the board progress through the following states:
 
     Contributors who took the time to implement concrete change proposals should not wait indefinitely.
 
-  - Prioritise fixing bugs over documentation, improvements or new features
+  - Prioritise fixing bugs and testing over documentation, improvements or new features
 
     The team values stability and accessibility higher than raw functionality.
 

mk/patterns.mk

@@ -1,10 +1,10 @@
 $(buildprefix)%.o: %.cc
 	@mkdir -p "$(dir $@)"
-	$(trace-cxx) $(CXX) -o $@ -c $< $(CPPFLAGS) $(GLOBAL_CXXFLAGS_PCH) $(GLOBAL_CXXFLAGS) $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(call filename-to-dep, $@) -MP
+	$(trace-cxx) $(CXX) -o $@ -c $< $(CPPFLAGS) $(GLOBAL_CXXFLAGS_PCH) $(GLOBAL_CXXFLAGS) $(CXXFLAGS) $($@_CXXFLAGS) $(ERROR_SWITCH_ENUM) -MMD -MF $(call filename-to-dep, $@) -MP
 
 $(buildprefix)%.o: %.cpp
 	@mkdir -p "$(dir $@)"
-	$(trace-cxx) $(CXX) -o $@ -c $< $(CPPFLAGS) $(GLOBAL_CXXFLAGS_PCH) $(GLOBAL_CXXFLAGS) $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(call filename-to-dep, $@) -MP
+	$(trace-cxx) $(CXX) -o $@ -c $< $(CPPFLAGS) $(GLOBAL_CXXFLAGS_PCH) $(GLOBAL_CXXFLAGS) $(CXXFLAGS) $($@_CXXFLAGS) $(ERROR_SWITCH_ENUM) -MMD -MF $(call filename-to-dep, $@) -MP
 
 $(buildprefix)%.o: %.c
 	@mkdir -p "$(dir $@)"

src/libcmd/installables.cc

@@ -102,6 +102,28 @@ MixFlakeOptions::MixFlakeOptions()
         }}
     });
 
+    addFlag({
+        .longName = "reference-lock-file",
+        .description = "Read the given lock file instead of `flake.lock` within the top-level flake.",
+        .category = category,
+        .labels = {"flake-lock-path"},
+        .handler = {[&](std::string lockFilePath) {
+            lockFlags.referenceLockFilePath = lockFilePath;
+        }},
+        .completer = completePath
+    });
+
+    addFlag({
+        .longName = "output-lock-file",
+        .description = "Write the given lock file instead of `flake.lock` within the top-level flake.",
+        .category = category,
+        .labels = {"flake-lock-path"},
+        .handler = {[&](std::string lockFilePath) {
+            lockFlags.outputLockFilePath = lockFilePath;
+        }},
+        .completer = completePath
+    });
+
     addFlag({
         .longName = "inputs-from",
         .description = "Use the inputs of the specified flake as registry entries.",

src/libcmd/repl.cc

@@ -252,7 +252,9 @@ void NixRepl::mainLoop()
     el_hist_size = 1000;
 #endif
     read_history(historyFile.c_str());
+    auto oldRepl = curRepl;
     curRepl = this;
+    Finally restoreRepl([&] { curRepl = oldRepl; });
 #ifndef READLINE
     rl_set_complete_func(completionCallback);
     rl_set_list_possib_func(listPossibleCallback);
@@ -1024,6 +1026,8 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
         str << v.fpoint;
         break;
 
+    case nThunk:
+    case nExternal:
     default:
         str << ANSI_RED "«unknown»" ANSI_NORMAL;
         break;

src/libexpr/eval.cc

@@ -173,7 +173,17 @@ void Value::print(const SymbolTable & symbols, std::ostream & str,
     case tFloat:
         str << fpoint;
         break;
+    case tBlackhole:
+        // Although we know for sure that it's going to be an infinite recursion
+        // when this value is accessed _in the current context_, it's likely
+        // that the user will misinterpret a simpler «infinite recursion» output
+        // as a definitive statement about the value, while in fact it may be
+        // a valid value after `builtins.trace` and perhaps some other steps
+        // have completed.
+        str << "«potential infinite recursion»";
+        break;
     default:
+        printError("Nix evaluator internal error: Value::print(): invalid value type %1%", internalType);
         abort();
     }
 }
@@ -229,6 +239,9 @@ std::string_view showType(ValueType type)
 
 std::string showType(const Value & v)
 {
+    // Allow selecting a subset of enum values
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wswitch-enum"
     switch (v.internalType) {
         case tString: return v.string.context ? "a string with context" : "a string";
         case tPrimOp:
@@ -242,16 +255,21 @@ std::string showType(const Value & v)
     default:
         return std::string(showType(v.type()));
     }
+    #pragma GCC diagnostic pop
 }
 
 PosIdx Value::determinePos(const PosIdx pos) const
 {
+    // Allow selecting a subset of enum values
+    #pragma GCC diagnostic push
+    #pragma GCC diagnostic ignored "-Wswitch-enum"
     switch (internalType) {
         case tAttrs: return attrs->pos;
         case tLambda: return lambda.fun->pos;
         case tApp: return app.left->determinePos(pos);
         default: return pos;
     }
+    #pragma GCC diagnostic pop
 }
 
 bool Value::isTrivial() const
@@ -2327,6 +2345,7 @@ bool EvalState::eqValues(Value & v1, Value & v2, const PosIdx pos, std::string_v
         case nFloat:
             return v1.fpoint == v2.fpoint;
 
+        case nThunk: // Must not be left by forceValue
         default:
             error("cannot compare %1% with %2%", showType(v1), showType(v2)).withTrace(pos, errorCtx).debugThrow<EvalError>();
     }

src/libexpr/flake/flake.cc

@@ -125,6 +125,9 @@ static FlakeInput parseFlakeInput(EvalState & state,
                 follows.insert(follows.begin(), lockRootPath.begin(), lockRootPath.end());
                 input.follows = follows;
             } else {
+                // Allow selecting a subset of enum values
+                #pragma GCC diagnostic push
+                #pragma GCC diagnostic ignored "-Wswitch-enum"
                 switch (attr.value->type()) {
                     case nString:
                         attrs.emplace(state.symbols[attr.name], attr.value->string.s);
@@ -139,6 +142,7 @@ static FlakeInput parseFlakeInput(EvalState & state,
                         throw TypeError("flake input attribute '%s' is %s while a string, Boolean, or integer is expected",
                             state.symbols[attr.name], showType(*attr.value));
                 }
+                #pragma GCC diagnostic pop
             }
         } catch (Error & e) {
             e.addTrace(
@@ -334,10 +338,14 @@ LockedFlake lockFlake(
     }
 
     try {
+        if (!fetchSettings.allowDirty && lockFlags.referenceLockFilePath) {
+            throw Error("reference lock file was provided, but the `allow-dirty` setting is set to false");
+        }
 
         // FIXME: symlink attack
         auto oldLockFile = LockFile::read(
-            flake.sourceInfo->actualPath + "/" + flake.lockedRef.subdir + "/flake.lock");
+            lockFlags.referenceLockFilePath.value_or(
+                flake.sourceInfo->actualPath + "/" + flake.lockedRef.subdir + "/flake.lock"));
 
         debug("old lock file: %s", oldLockFile);
 
@@ -619,13 +627,20 @@ LockedFlake lockFlake(
 
         debug("new lock file: %s", newLockFile);
 
+        auto relPath = (topRef.subdir == "" ? "" : topRef.subdir + "/") + "flake.lock";
+        auto sourcePath = topRef.input.getSourcePath();
+        auto outputLockFilePath = sourcePath ? std::optional{*sourcePath + "/" + relPath} : std::nullopt;
+        if (lockFlags.outputLockFilePath) {
+            outputLockFilePath = lockFlags.outputLockFilePath;
+        }
+
         /* Check whether we need to / can write the new lock file. */
-        if (!(newLockFile == oldLockFile)) {
+        if (newLockFile != oldLockFile || lockFlags.outputLockFilePath) {
 
             auto diff = LockFile::diff(oldLockFile, newLockFile);
 
             if (lockFlags.writeLockFile) {
-                if (auto sourcePath = topRef.input.getSourcePath()) {
+                if (outputLockFilePath) {
                     if (auto unlockedInput = newLockFile.isUnlocked()) {
                         if (fetchSettings.warnDirty)
                             warn("will not write lock file of flake '%s' because it has an unlocked input ('%s')", topRef, *unlockedInput);
@@ -633,25 +648,24 @@ LockedFlake lockFlake(
                         if (!lockFlags.updateLockFile)
                             throw Error("flake '%s' requires lock file changes but they're not allowed due to '--no-update-lock-file'", topRef);
 
-                        auto relPath = (topRef.subdir == "" ? "" : topRef.subdir + "/") + "flake.lock";
+                        bool lockFileExists = pathExists(*outputLockFilePath);
-
-                        auto path = *sourcePath + "/" + relPath;
-
-                        bool lockFileExists = pathExists(path);
 
                         if (lockFileExists) {
                             auto s = chomp(diff);
                             if (s.empty())
-                                warn("updating lock file '%s'", path);
+                                warn("updating lock file '%s'", *outputLockFilePath);
                             else
-                                warn("updating lock file '%s':\n%s", path, s);
+                                warn("updating lock file '%s':\n%s", *outputLockFilePath, s);
                         } else
-                            warn("creating lock file '%s'", path);
+                            warn("creating lock file '%s'", *outputLockFilePath);
 
-                        newLockFile.write(path);
+                        newLockFile.write(*outputLockFilePath);
 
                         std::optional<std::string> commitMessage = std::nullopt;
                         if (lockFlags.commitLockFile) {
+                            if (lockFlags.outputLockFilePath) {
+                                throw Error("--commit-lock-file and --output-lock-file are currently incompatible");
+                            }
                             std::string cm;
 
                             cm = fetchSettings.commitLockFileSummary.get();

src/libexpr/flake/flake.hh

@@ -118,6 +118,12 @@ struct LockFlags
     /* Whether to commit changes to flake.lock. */
     bool commitLockFile = false;
 
+    /* The path to a lock file to read instead of the `flake.lock` file in the top-level flake */
+    std::optional<std::string> referenceLockFilePath;
+
+    /* The path to a lock file to write to instead of the `flake.lock` file in the top-level flake */
+    std::optional<Path> outputLockFilePath;
+
     /* Flake inputs to be overridden. */
     std::map<InputPath, FlakeRef> inputOverrides;
 

src/libexpr/local.mk

@@ -46,3 +46,5 @@ $(foreach i, $(wildcard src/libexpr/flake/*.hh), \
 $(d)/primops.cc: $(d)/imported-drv-to-derivation.nix.gen.hh $(d)/primops/derivation.nix.gen.hh $(d)/fetchurl.nix.gen.hh
 
 $(d)/flake/flake.cc: $(d)/flake/call-flake.nix.gen.hh
+
+src/libexpr/primops/fromTOML.o:	ERROR_SWITCH_ENUM =

src/libexpr/primops.cc

@@ -577,6 +577,9 @@ struct CompareValues
                 return v1->integer < v2->fpoint;
             if (v1->type() != v2->type())
                 state.error("cannot compare %s with %s", showType(*v1), showType(*v2)).debugThrow<EvalError>();
+            // Allow selecting a subset of enum values
+            #pragma GCC diagnostic push
+            #pragma GCC diagnostic ignored "-Wswitch-enum"
             switch (v1->type()) {
                 case nInt:
                     return v1->integer < v2->integer;
@@ -599,6 +602,7 @@ struct CompareValues
                     }
                 default:
                     state.error("cannot compare %s with %s; values of that type are incomparable", showType(*v1), showType(*v2)).debugThrow<EvalError>();
+            #pragma GCC diagnostic pop
             }
         } catch (Error & e) {
             if (!errorCtx.empty())

src/libstore/build-result.hh

@@ -53,6 +53,7 @@ struct BuildResult
                 case LogLimitExceeded: return "LogLimitExceeded";
                 case NotDeterministic: return "NotDeterministic";
                 case ResolvesToAlreadyValid: return "ResolvesToAlreadyValid";
+                case NoSubstituters: return "NoSubstituters";
                 default: return "Unknown";
             };
         }();

src/libstore/filetransfer.cc

@@ -407,6 +407,10 @@ struct curlFileTransfer : public FileTransfer
                     err = Misc;
                 } else {
                     // Don't bother retrying on certain cURL errors either
+
+                    // Allow selecting a subset of enum values
+                    #pragma GCC diagnostic push
+                    #pragma GCC diagnostic ignored "-Wswitch-enum"
                     switch (code) {
                         case CURLE_FAILED_INIT:
                         case CURLE_URL_MALFORMAT:
@@ -427,6 +431,7 @@ struct curlFileTransfer : public FileTransfer
                         default: // Shut up warnings
                             break;
                     }
+                    #pragma GCC diagnostic pop
                 }
 
                 attempt++;

src/libstore/local-store.cc

@@ -1134,54 +1134,6 @@ StorePathSet LocalStore::querySubstitutablePaths(const StorePathSet & paths)
 }
 
 
-// FIXME: move this, it's not specific to LocalStore.
-void LocalStore::querySubstitutablePathInfos(const StorePathCAMap & paths, SubstitutablePathInfos & infos)
-{
-    if (!settings.useSubstitutes) return;
-    for (auto & sub : getDefaultSubstituters()) {
-        for (auto & path : paths) {
-            if (infos.count(path.first))
-                // Choose first succeeding substituter.
-                continue;
-
-            auto subPath(path.first);
-
-            // Recompute store path so that we can use a different store root.
-            if (path.second) {
-                subPath = makeFixedOutputPathFromCA(path.first.name(), *path.second);
-                if (sub->storeDir == storeDir)
-                    assert(subPath == path.first);
-                if (subPath != path.first)
-                    debug("replaced path '%s' with '%s' for substituter '%s'", printStorePath(path.first), sub->printStorePath(subPath), sub->getUri());
-            } else if (sub->storeDir != storeDir) continue;
-
-            debug("checking substituter '%s' for path '%s'", sub->getUri(), sub->printStorePath(subPath));
-            try {
-                auto info = sub->queryPathInfo(subPath);
-
-                if (sub->storeDir != storeDir && !(info->isContentAddressed(*sub) && info->references.empty()))
-                    continue;
-
-                auto narInfo = std::dynamic_pointer_cast<const NarInfo>(
-                    std::shared_ptr<const ValidPathInfo>(info));
-                infos.insert_or_assign(path.first, SubstitutablePathInfo{
-                    info->deriver,
-                    info->references,
-                    narInfo ? narInfo->fileSize : 0,
-                    info->narSize});
-            } catch (InvalidPath &) {
-            } catch (SubstituterDisabled &) {
-            } catch (Error & e) {
-                if (settings.tryFallback)
-                    logError(e.info());
-                else
-                    throw;
-            }
-        }
-    }
-}
-
-
 void LocalStore::registerValidPath(const ValidPathInfo & info)
 {
     registerValidPaths({{info.path, info}});

src/libstore/local-store.hh

@@ -134,9 +134,6 @@ public:
 
     StorePathSet querySubstitutablePaths(const StorePathSet & paths) override;
 
-    void querySubstitutablePathInfos(const StorePathCAMap & paths,
-        SubstitutablePathInfos & infos) override;
-
     bool pathInfoIsUntrusted(const ValidPathInfo &) override;
     bool realisationIsUntrusted(const Realisation & ) override;
 

src/libstore/nar-accessor.cc

@@ -275,6 +275,7 @@ json listNar(ref<FSAccessor> accessor, const Path & path, bool recurse)
         obj["type"] = "symlink";
         obj["target"] = accessor->readLink(path);
         break;
+    case FSAccessor::Type::tMissing:
     default:
         throw Error("path '%s' does not exist in NAR", path);
     }

src/libstore/store-api.cc

@@ -507,6 +507,54 @@ StorePathSet Store::queryDerivationOutputs(const StorePath & path)
     return outputPaths;
 }
 
+
+void Store::querySubstitutablePathInfos(const StorePathCAMap & paths, SubstitutablePathInfos & infos)
+{
+    if (!settings.useSubstitutes) return;
+    for (auto & sub : getDefaultSubstituters()) {
+        for (auto & path : paths) {
+            if (infos.count(path.first))
+                // Choose first succeeding substituter.
+                continue;
+
+            auto subPath(path.first);
+
+            // Recompute store path so that we can use a different store root.
+            if (path.second) {
+                subPath = makeFixedOutputPathFromCA(path.first.name(), *path.second);
+                if (sub->storeDir == storeDir)
+                    assert(subPath == path.first);
+                if (subPath != path.first)
+                    debug("replaced path '%s' with '%s' for substituter '%s'", printStorePath(path.first), sub->printStorePath(subPath), sub->getUri());
+            } else if (sub->storeDir != storeDir) continue;
+
+            debug("checking substituter '%s' for path '%s'", sub->getUri(), sub->printStorePath(subPath));
+            try {
+                auto info = sub->queryPathInfo(subPath);
+
+                if (sub->storeDir != storeDir && !(info->isContentAddressed(*sub) && info->references.empty()))
+                    continue;
+
+                auto narInfo = std::dynamic_pointer_cast<const NarInfo>(
+                    std::shared_ptr<const ValidPathInfo>(info));
+                infos.insert_or_assign(path.first, SubstitutablePathInfo{
+                    info->deriver,
+                    info->references,
+                    narInfo ? narInfo->fileSize : 0,
+                    info->narSize});
+            } catch (InvalidPath &) {
+            } catch (SubstituterDisabled &) {
+            } catch (Error & e) {
+                if (settings.tryFallback)
+                    logError(e.info());
+                else
+                    throw;
+            }
+        }
+    }
+}
+
+
 bool Store::isValidPath(const StorePath & storePath)
 {
     {

src/libstore/store-api.hh

@@ -456,7 +456,7 @@ public:
      * resulting ‘infos’ map.
      */
     virtual void querySubstitutablePathInfos(const StorePathCAMap & paths,
-        SubstitutablePathInfos & infos) { return; };
+        SubstitutablePathInfos & infos);
 
     /**
      * Import a path into the store.

src/libutil/args.cc

@@ -236,8 +236,6 @@ nlohmann::json Args::toJSON()
     auto flags = nlohmann::json::object();
 
     for (auto & [name, flag] : longFlags) {
-        /* Skip experimental flags when listing flags. */
-        if (!experimentalFeatureSettings.isEnabled(flag->experimentalFeature)) continue;
         auto j = nlohmann::json::object();
         if (flag->aliases.count(name)) continue;
         if (flag->shortName)
@@ -249,6 +247,11 @@ nlohmann::json Args::toJSON()
             j["arity"] = flag->handler.arity;
         if (!flag->labels.empty())
             j["labels"] = flag->labels;
+        // TODO With C++23 use `std::optional::tranform`
+        if (auto & xp = flag->experimentalFeature)
+            j["experimental-feature"] = showExperimentalFeature(*xp);
+        else
+            j["experimental-feature"] = nullptr;
         flags[name] = std::move(j);
     }
 
@@ -345,6 +348,11 @@ Strings argvToStrings(int argc, char * * argv)
     return args;
 }
 
+std::optional<ExperimentalFeature> Command::experimentalFeature ()
+{
+    return { Xp::NixCommand };
+}
+
 MultiCommand::MultiCommand(const Commands & commands_)
     : commands(commands_)
 {
@@ -408,6 +416,11 @@ nlohmann::json MultiCommand::toJSON()
         cat["id"] = command->category();
         cat["description"] = trim(categories[command->category()]);
         j["category"] = std::move(cat);
+        // TODO With C++23 use `std::optional::tranform`
+        if (auto xp = command->experimentalFeature())
+            cat["experimental-feature"] = showExperimentalFeature(*xp);
+        else
+            cat["experimental-feature"] = nullptr;
         cmds[name] = std::move(j);
     }
 

src/libutil/args.hh

@@ -236,6 +236,8 @@ struct Command : virtual public Args
 
     static constexpr Category catDefault = 0;
 
+    virtual std::optional<ExperimentalFeature> experimentalFeature ();
+
     virtual Category category() { return catDefault; }
 };
 

src/libutil/logging.cc

@@ -65,9 +65,10 @@ public:
             switch (lvl) {
             case lvlError: c = '3'; break;
             case lvlWarn: c = '4'; break;
-            case lvlInfo: c = '5'; break;
+            case lvlNotice: case lvlInfo: c = '5'; break;
             case lvlTalkative: case lvlChatty: c = '6'; break;
-            default: c = '7';
+            case lvlDebug: case lvlVomit: c = '7';
+            default: c = '7'; break; // should not happen, and missing enum case is reported by -Werror=switch-enum
             }
             prefix = std::string("<") + c + ">";
         }

src/nix-store/nix-store.cc

@@ -277,17 +277,17 @@ static void printTree(const StorePath & path,
 static void opQuery(Strings opFlags, Strings opArgs)
 {
     enum QueryType
-        { qDefault, qOutputs, qRequisites, qReferences, qReferrers
+        { qOutputs, qRequisites, qReferences, qReferrers
         , qReferrersClosure, qDeriver, qBinding, qHash, qSize
         , qTree, qGraph, qGraphML, qResolve, qRoots };
-    QueryType query = qDefault;
+    std::optional<QueryType> query;
     bool useOutput = false;
     bool includeOutputs = false;
     bool forceRealise = false;
     std::string bindingName;
 
     for (auto & i : opFlags) {
-        QueryType prev = query;
+        std::optional<QueryType> prev = query;
         if (i == "--outputs") query = qOutputs;
         else if (i == "--requisites" || i == "-R") query = qRequisites;
         else if (i == "--references") query = qReferences;
@@ -312,15 +312,15 @@ static void opQuery(Strings opFlags, Strings opArgs)
         else if (i == "--force-realise" || i == "--force-realize" || i == "-f") forceRealise = true;
         else if (i == "--include-outputs") includeOutputs = true;
         else throw UsageError("unknown flag '%1%'", i);
-        if (prev != qDefault && prev != query)
+        if (prev && prev != query)
             throw UsageError("query type '%1%' conflicts with earlier flag", i);
     }
 
-    if (query == qDefault) query = qOutputs;
+    if (!query) query = qOutputs;
 
     RunPager pager;
 
-    switch (query) {
+    switch (*query) {
 
         case qOutputs: {
             for (auto & i : opArgs) {

src/nix/doctor.cc

@@ -39,6 +39,14 @@ struct CmdDoctor : StoreCommand
 {
     bool success = true;
 
+    /**
+     * This command is stable before the others
+     */
+    std::optional<ExperimentalFeature> experimentalFeature() override
+    {
+        return std::nullopt;
+    }
+
     std::string description() override
     {
         return "check your system for potential problems and print a PASS or FAIL for each check";

src/nix/main.cc

@@ -83,6 +83,7 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
             .description = "Print full build logs on standard error.",
             .category = loggingCategory,
             .handler = {[&]() { logger->setPrintBuildLogs(true); }},
+            .experimentalFeature = Xp::NixCommand,
         });
 
         addFlag({
@@ -98,6 +99,7 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
             .description = "Disable substituters and consider all previously downloaded files up-to-date.",
             .category = miscCategory,
             .handler = {[&]() { useNet = false; }},
+            .experimentalFeature = Xp::NixCommand,
         });
 
         addFlag({
@@ -105,6 +107,7 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
             .description = "Consider all previously downloaded files out-of-date.",
             .category = miscCategory,
             .handler = {[&]() { refresh = true; }},
+            .experimentalFeature = Xp::NixCommand,
         });
     }
 
@@ -420,10 +423,8 @@ void mainWrapped(int argc, char * * argv)
     if (!args.command)
         throw UsageError("no subcommand specified");
 
-    if (args.command->first != "repl"
+    experimentalFeatureSettings.require(
-        && args.command->first != "doctor"
+        args.command->second->experimentalFeature());
-        && args.command->first != "upgrade-nix")
-        experimentalFeatureSettings.require(Xp::NixCommand);
 
     if (args.useNet && !haveInternet()) {
         warn("you don't have Internet access; disabling some network-dependent features");

src/nix/repl.cc

@@ -12,6 +12,14 @@ struct CmdRepl : RawInstallablesCommand
         evalSettings.pureEval = false;
     }
 
+    /**
+     * This command is stable before the others
+     */
+    std::optional<ExperimentalFeature> experimentalFeature() override
+    {
+        return std::nullopt;
+    }
+
     std::vector<std::string> files;
 
     Strings getDefaultFlakeAttrPaths() override

src/nix/upgrade-nix.cc

@@ -32,6 +32,14 @@ struct CmdUpgradeNix : MixDryRun, StoreCommand
         });
     }
 
+    /**
+     * This command is stable before the others
+     */
+    std::optional<ExperimentalFeature> experimentalFeature() override
+    {
+        return std::nullopt;
+    }
+
     std::string description() override
     {
         return "upgrade Nix to the stable version declared in Nixpkgs";

tests/experimental-features.sh

@@ -15,9 +15,26 @@ function both_ways {
 # Simple case, the configuration effects the running command
 both_ways show-config
 
-# Complicated case, earlier args effect later args
+# Skipping for now, because we actually *do* want these to show up in
+# the manual, just be marked experimental. Will reenable once the manual
+# generation takes advantage of the JSON metadata on this.
 
-both_ways store gc --help
+# both_ways store gc --help
 
 expect 1 nix --experimental-features 'nix-command' show-config --flake-registry 'https://no'
 nix --experimental-features 'nix-command flakes' show-config --flake-registry 'https://no'
+
+# Double check these are stable
+nix --experimental-features '' --help
+nix --experimental-features '' doctor --help
+nix --experimental-features '' repl --help
+nix --experimental-features '' upgrade-nix --help
+
+# These 3 arguments are currently given to all commands, which is wrong (as not
+# all care). To deal with fixing later, we simply make them require the
+# nix-command experimental features --- it so happens that the commands we wish
+# stabilizing to do not need them anyways.
+for arg in '--print-build-logs' '--offline' '--refresh'; do
+    nix --experimental-features 'nix-command' "$arg" --help
+    ! nix --experimental-features '' "$arg" --help
+done

tests/flakes/flakes.sh

@@ -96,7 +96,9 @@ json=$(nix flake metadata flake1 --json | jq .)
 hash1=$(echo "$json" | jq -r .revision)
 
 echo -n '# foo' >> $flake1Dir/flake.nix
+flake1OriginalCommit=$(git -C $flake1Dir rev-parse HEAD)
 git -C $flake1Dir commit -a -m 'Foo'
+flake1NewCommit=$(git -C $flake1Dir rev-parse HEAD)
 hash2=$(nix flake metadata flake1 --json --refresh | jq -r .revision)
 [[ $hash1 != $hash2 ]]
 
@@ -491,3 +493,14 @@ nix store delete $(nix store add-path $badFlakeDir)
 [[ $(nix-instantiate --eval flake:git+file://$flake3Dir -A x) = 123 ]]
 [[ $(nix-instantiate -I flake3=flake:flake3 --eval '<flake3>' -A x) = 123 ]]
 [[ $(NIX_PATH=flake3=flake:flake3 nix-instantiate --eval '<flake3>' -A x) = 123 ]]
+
+# Test alternate lockfile paths.
+nix flake lock $flake2Dir --output-lock-file $TEST_ROOT/flake2.lock
+cmp $flake2Dir/flake.lock $TEST_ROOT/flake2.lock >/dev/null # lockfiles should be identical, since we're referencing flake2's original one
+
+nix flake lock $flake2Dir --output-lock-file $TEST_ROOT/flake2-overridden.lock --override-input flake1 git+file://$flake1Dir?rev=$flake1OriginalCommit
+expectStderr 1 cmp $flake2Dir/flake.lock $TEST_ROOT/flake2-overridden.lock
+nix flake metadata $flake2Dir --reference-lock-file $TEST_ROOT/flake2-overridden.lock | grepQuiet $flake1OriginalCommit
+
+# reference-lock-file can only be used if allow-dirty is set.
+expectStderr 1 nix flake metadata $flake2Dir --no-allow-dirty --reference-lock-file $TEST_ROOT/flake2-overridden.lock

tests/lang.sh

@@ -5,12 +5,19 @@ export NIX_REMOTE=dummy://
 export NIX_STORE_DIR=/nix/store
 
 nix-instantiate --eval -E 'builtins.trace "Hello" 123' 2>&1 | grepQuiet Hello
+nix-instantiate --eval -E 'builtins.trace "Hello" 123' 2>/dev/null | grepQuiet 123
 nix-instantiate --eval -E 'builtins.addErrorContext "Hello" 123' 2>&1
 nix-instantiate --trace-verbose --eval -E 'builtins.traceVerbose "Hello" 123' 2>&1 | grepQuiet Hello
 nix-instantiate --eval -E 'builtins.traceVerbose "Hello" 123' 2>&1 | grepQuietInverse Hello
 nix-instantiate --show-trace --eval -E 'builtins.addErrorContext "Hello" 123' 2>&1 | grepQuietInverse Hello
 expectStderr 1 nix-instantiate --show-trace --eval -E 'builtins.addErrorContext "Hello" (throw "Foo")' | grepQuiet Hello
 
+nix-instantiate --eval -E 'let x = builtins.trace { x = x; } true; in x' \
+  2>&1 | grepQuiet -E 'trace: { x = «potential infinite recursion»; }'
+
+nix-instantiate --eval -E 'let x = { repeating = x; tracing = builtins.trace x true; }; in x.tracing'\
+  2>&1 | grepQuiet -F 'trace: { repeating = «repeated»; tracing = «potential infinite recursion»; }'
+
 set +x
 
 fail=0