Make the loggers truly pluggable

Remove the static list of possible loggers, and instead generate it
dynamically from the registered ones.

This requires a conceptually small but textually invasive refactoring as
to remove some undefined behavior wrt. the orders in which static
variables are initialised, we change `nix::config` from a static
variable to a function that lazily builds a `Config` object and returns
it (the reason for that is that with a static `Config`, we might − and
apparantly do in practice − get the list of registered loggers before
they are all registered, leading to an incomplete list in the
help/man/completion).

doc/manual/command-ref/conf-file.xml

@@ -613,7 +613,7 @@ password <replaceable>my-password</replaceable>
         RegisterStoreImplementation to add new store implementations,
         RegisterCommand to add new subcommands to the
         <literal>nix</literal> command, and RegisterSetting to add new
-        nix config settings. See the constructors for those types for
+        nix config settings()-> See the constructors for those types for
         more details.
       </para>
       <para>

perl/lib/Nix/Store.xs

@@ -28,7 +28,7 @@ static ref<Store> store()
     if (!_store) {
         try {
             loadConfFile();
-            settings.lockCPU = false;
+            settings()->lockCPU = false;
             _store = openStore();
         } catch (Error & e) {
             croak("%s", e.what());
@@ -355,9 +355,9 @@ void addTempRoot(char * storePath)
 
 SV * getBinDir()
     PPCODE:
-        XPUSHs(sv_2mortal(newSVpv(settings.nixBinDir.c_str(), 0)));
+        XPUSHs(sv_2mortal(newSVpv(settings()->nixBinDir.c_str(), 0)));
 
 
 SV * getStoreDir()
     PPCODE:
-        XPUSHs(sv_2mortal(newSVpv(settings.nixStore.c_str(), 0)));
+        XPUSHs(sv_2mortal(newSVpv(settings()->nixStore.c_str(), 0)));

src/build-remote/build-remote.cc

@@ -60,14 +60,14 @@ static int _main(int argc, char * * argv)
 
         FdSource source(STDIN_FILENO);
 
-        /* Read the parent's settings. */
+        /* Read the parent's settings()-> */
         while (readInt(source)) {
             auto name = readString(source);
             auto value = readString(source);
-            settings.set(name, value);
+            settings()->set(name, value);
         }
 
-        settings.maxBuildJobs.set("1"); // hack to make tests with local?root= work
+        settings()->maxBuildJobs.set("1"); // hack to make tests with local?root= work
 
         initPlugins();
 
@@ -104,8 +104,8 @@ static int _main(int argc, char * * argv)
             auto requiredFeatures = readStrings<std::set<std::string>>(source);
 
             auto canBuildLocally = amWilling
-                 &&  (  neededSystem == settings.thisSystem
-                     || settings.extraPlatforms.get().count(neededSystem) > 0)
+                 &&  (  neededSystem == settings()->thisSystem
+                     || settings()->extraPlatforms.get().count(neededSystem) > 0)
                  &&  allSupportedLocally(*store, requiredFeatures);
 
             /* Error ignored here, will be caught later */
@@ -265,7 +265,7 @@ static int _main(int argc, char * * argv)
             signal(SIGALRM, old);
         }
 
-        auto substitute = settings.buildersUseSubstitutes ? Substitute : NoSubstitute;
+        auto substitute = settings()->buildersUseSubstitutes ? Substitute : NoSubstitute;
 
         {
             Activity act(*logger, lvlTalkative, actUnknown, fmt("copying dependencies to '%s'", storeUri));

src/libexpr/eval-cache.cc

@@ -606,7 +606,7 @@ StorePath AttrCursor::forceDerivation()
 {
     auto aDrvPath = getAttr(root->state.sDrvPath, true);
     auto drvPath = root->state.store->parseStorePath(aDrvPath->getString());
-    if (!root->state.store->isValidPath(drvPath) && !settings.readOnlyMode) {
+    if (!root->state.store->isValidPath(drvPath) && !settings()->readOnlyMode) {
         /* The eval cache contains 'drvPath', but the actual path has
            been garbage-collected. So force it to be regenerated. */
         aDrvPath->forceValue();

src/libexpr/eval.cc

@@ -372,7 +372,7 @@ EvalState::EvalState(const Strings & _searchPath, ref<Store> store)
     }
 
     try {
-        addToSearchPath("nix=" + canonPath(settings.nixDataDir + "/nix/corepkgs", true));
+        addToSearchPath("nix=" + canonPath(settings()->nixDataDir + "/nix/corepkgs", true));
     } catch (Error &) {
     }
 
@@ -1820,7 +1820,7 @@ string EvalState::copyPathToStore(PathSet & context, const Path & path)
     if (i != srcToStore.end())
         dstPath = store->printStorePath(i->second);
     else {
-        auto p = settings.readOnlyMode
+        auto p = settings()->readOnlyMode
             ? store->computeStorePathForPath(std::string(baseNameOf(path)), checkSourcePath(path)).first
             : store->addToStore(std::string(baseNameOf(path)), checkSourcePath(path), FileIngestionMethod::Recursive, htSHA256, defaultPathFilter, repair);
         dstPath = store->printStorePath(p);
@@ -2073,8 +2073,8 @@ Strings EvalSettings::getDefaultNixPath()
     Strings res;
     auto add = [&](const Path & p) { if (pathExists(p)) { res.push_back(p); } };
     add(getHome() + "/.nix-defexpr/channels");
-    add("nixpkgs=" + settings.nixStateDir + "/nix/profiles/per-user/root/channels/nixpkgs");
-    add(settings.nixStateDir + "/nix/profiles/per-user/root/channels");
+    add("nixpkgs=" + settings()->nixStateDir + "/nix/profiles/per-user/root/channels/nixpkgs");
+    add(settings()->nixStateDir + "/nix/profiles/per-user/root/channels");
     return res;
 }
 

src/libexpr/flake/flake.cc

@@ -254,7 +254,7 @@ LockedFlake lockFlake(
     const FlakeRef & topRef,
     const LockFlags & lockFlags)
 {
-    settings.requireExperimentalFeature("flakes");
+    settings()->requireExperimentalFeature("flakes");
 
     FlakeCache flakeCache;
 
@@ -481,7 +481,7 @@ LockedFlake lockFlake(
         if (lockFlags.writeLockFile) {
             if (auto sourcePath = topRef.input.getSourcePath()) {
                 if (!newLockFile.isImmutable()) {
-                    if (settings.warnDirty)
+                    if (settings()->warnDirty)
                         warn("will not write lock file of flake '%s' because it has a mutable input", topRef);
                 } else {
                     if (!lockFlags.updateLockFile)

src/libexpr/parser.y

@@ -415,7 +415,7 @@ expr_simple
           new ExprString(data->symbols.create(path)));
   }
   | URI {
-      static bool noURLLiterals = settings.isExperimentalFeatureEnabled("no-url-literals");
+      static bool noURLLiterals = settings()->isExperimentalFeatureEnabled("no-url-literals");
       if (noURLLiterals)
           throw ParseError({
               .hint = hintfmt("URL literals are disabled"),

src/libexpr/primops.cc

@@ -906,7 +906,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             }
 
             if (i->name == state.sContentAddressed) {
-                settings.requireExperimentalFeature("ca-derivations");
+                settings()->requireExperimentalFeature("ca-derivations");
                 contentAddressed = state.forceBool(*i->value, pos);
             }
 
@@ -1204,7 +1204,7 @@ static void prim_storePath(EvalState & state, const Pos & pos, Value * * args, V
             .errPos = pos
         });
     auto path2 = state.store->toStorePath(path).first;
-    if (!settings.readOnlyMode)
+    if (!settings()->readOnlyMode)
         state.store->ensurePath(path2);
     context.insert(state.store->printStorePath(path2));
     mkString(v, path, context);
@@ -1643,7 +1643,7 @@ static void prim_toFile(EvalState & state, const Pos & pos, Value * * args, Valu
         refs.insert(state.store->parseStorePath(path));
     }
 
-    auto storePath = state.store->printStorePath(settings.readOnlyMode
+    auto storePath = state.store->printStorePath(settings()->readOnlyMode
         ? state.store->computeStorePathForText(name, contents, refs)
         : state.store->addTextToStore(name, contents, refs, state.repair));
 
@@ -1767,7 +1767,7 @@ static void addPath(EvalState & state, const Pos & pos, const string & name, con
         expectedStorePath = state.store->makeFixedOutputPath(method, *expectedHash, name);
     Path dstPath;
     if (!expectedHash || !state.store->isValidPath(*expectedStorePath)) {
-        dstPath = state.store->printStorePath(settings.readOnlyMode
+        dstPath = state.store->printStorePath(settings()->readOnlyMode
             ? state.store->computeStorePathForPath(name, path, method, htSHA256, filter).first
             : state.store->addToStore(name, path, method, htSHA256, filter, state.repair));
         if (expectedHash && expectedStorePath != state.store->parseStorePath(dstPath))
@@ -3517,7 +3517,7 @@ void EvalState::createBaseEnv()
     }
 
     if (!evalSettings.pureEval) {
-        mkString(v, settings.thisSystem.get());
+        mkString(v, settings()->thisSystem.get());
         addConstant("__currentSystem", v);
     }
 
@@ -3554,7 +3554,7 @@ void EvalState::createBaseEnv()
 
     if (RegisterPrimOp::primOps)
         for (auto & primOp : *RegisterPrimOp::primOps)
-            if (!primOp.requiredFeature || settings.isExperimentalFeatureEnabled(*primOp.requiredFeature))
+            if (!primOp.requiredFeature || settings()->isExperimentalFeatureEnabled(*primOp.requiredFeature))
                 addPrimOp({
                     .fun = primOp.fun,
                     .arity = std::max(primOp.args.size(), primOp.arity),

src/libexpr/primops/context.cc

@@ -150,7 +150,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
                 .hint = hintfmt("Context key '%s' is not a store path", i.name),
                 .errPos = *i.pos
             });
-        if (!settings.readOnlyMode)
+        if (!settings()->readOnlyMode)
             state.store->ensurePath(state.store->parseStorePath(i.name));
         state.forceAttrs(*i.value, *i.pos);
         auto iter = i.value->attrs->find(sPath);

src/libexpr/primops/fetchTree.cc

@@ -148,7 +148,7 @@ static void fetchTree(
 
 static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    settings.requireExperimentalFeature("flakes");
+    settings()->requireExperimentalFeature("flakes");
     fetchTree(state, pos, args, v, std::nullopt);
 }
 

src/libfetchers/cache.cc

@@ -105,7 +105,7 @@ struct CacheImpl : Cache
             inAttrsJson, infoJson, store->printStorePath(storePath));
 
         return Result {
-            .expired = !immutable && (settings.tarballTtl.get() == 0 || timestamp + settings.tarballTtl < time(0)),
+            .expired = !immutable && (settings()->tarballTtl.get() == 0 || timestamp + settings()->tarballTtl < time(0)),
             .infoAttrs = jsonToAttrs(nlohmann::json::parse(infoJson)),
             .storePath = std::move(storePath)
         };

src/libfetchers/git.cc

@@ -235,10 +235,10 @@ struct GitInputScheme : InputScheme
 
                 /* This is an unclean working tree. So copy all tracked files. */
 
-                if (!settings.allowDirty)
+                if (!settings()->allowDirty)
                     throw Error("Git tree '%s' is dirty", actualUrl);
 
-                if (settings.warnDirty)
+                if (settings()->warnDirty)
                     warn("Git tree '%s' is dirty", actualUrl);
 
                 auto gitOpts = Strings({ "-C", actualUrl, "ls-files", "-z" });
@@ -341,7 +341,7 @@ struct GitInputScheme : InputScheme
                    git fetch to update the local ref to the remote ref. */
                 struct stat st;
                 doFetch = stat(localRefFile.c_str(), &st) != 0 ||
-                    (uint64_t) st.st_mtime + settings.tarballTtl <= (uint64_t) now;
+                    (uint64_t) st.st_mtime + settings()->tarballTtl <= (uint64_t) now;
             }
 
             if (doFetch) {

src/libfetchers/github.cc

@@ -184,7 +184,7 @@ struct GitHubInputScheme : GitArchiveInputScheme
 
     void addAccessToken(std::string & url) const
     {
-        std::string accessToken = settings.githubAccessToken.get();
+        std::string accessToken = settings()->githubAccessToken.get();
         if (accessToken != "")
             url += "?access_token=" + accessToken;
     }
@@ -257,7 +257,7 @@ struct GitLabInputScheme : GitArchiveInputScheme
             input.getRev()->to_string(Base16, false));
 
         /* # FIXME: add privat token auth (`curl --header "PRIVATE-TOKEN: <your_access_token>"`)
-        std::string accessToken = settings.githubAccessToken.get();
+        std::string accessToken = settings()->githubAccessToken.get();
         if (accessToken != "")
             url += "?access_token=" + accessToken;*/
 

src/libfetchers/mercurial.cc

@@ -136,10 +136,10 @@ struct MercurialInputScheme : InputScheme
                 /* This is an unclean working tree. So copy all tracked
                    files. */
 
-                if (!settings.allowDirty)
+                if (!settings()->allowDirty)
                     throw Error("Mercurial tree '%s' is unclean", actualUrl);
 
-                if (settings.warnDirty)
+                if (settings()->warnDirty)
                     warn("Mercurial tree '%s' is unclean", actualUrl);
 
                 input.attrs.insert_or_assign("ref", chomp(runProgram("hg", true, { "branch", "-R", actualUrl })));

src/libfetchers/registry.cc

@@ -101,7 +101,7 @@ void Registry::remove(const Input & input)
 
 static Path getSystemRegistryPath()
 {
-    return settings.nixConfDir + "/registry.json";
+    return settings()->nixConfDir + "/registry.json";
 }
 
 static std::shared_ptr<Registry> getSystemRegistry()
@@ -142,7 +142,7 @@ void overrideRegistry(
 static std::shared_ptr<Registry> getGlobalRegistry(ref<Store> store)
 {
     static auto reg = [&]() {
-        auto path = settings.flakeRegistry.get();
+        auto path = settings()->flakeRegistry.get();
 
         if (!hasPrefix(path, "/")) {
             auto storePath = downloadFile(store, path, "flake-registry.json", false).storePath;

src/libmain/common-args.cc

@@ -55,7 +55,7 @@ MixCommonArgs::MixCommonArgs(const string & programName)
         .description = "maximum number of parallel builds",
         .labels = Strings{"jobs"},
         .handler = {[=](std::string s) {
-            settings.set("max-jobs", s);
+            settings()->set("max-jobs", s);
         }}
     });
 

src/libmain/shared.cc

@@ -77,7 +77,7 @@ void printMissing(ref<Store> store, const StorePathSet & willBuild,
 
     if (!unknown.empty()) {
         printMsg(lvl, fmt("don't know how to build these paths%s:",
-                (settings.readOnlyMode ? " (may be caused by read-only store access)" : "")));
+                (settings()->readOnlyMode ? " (may be caused by read-only store access)" : "")));
         for (auto & i : unknown)
             printMsg(lvl, fmt("  %s", store->printStorePath(i)));
     }
@@ -182,33 +182,33 @@ LegacyArgs::LegacyArgs(const std::string & programName,
         .longName = "no-build-output",
         .shortName = 'Q',
         .description = "do not show build output",
-        .handler = {[&]() {setLogFormat(LogFormat::raw); }},
+        .handler = {[&]() {setLogFormat(LogFormat("raw")); }},
     });
 
     addFlag({
         .longName = "keep-failed",
         .shortName ='K',
         .description = "keep temporary directories of failed builds",
-        .handler = {&(bool&) settings.keepFailed, true},
+        .handler = {&(bool&) settings()->keepFailed, true},
     });
 
     addFlag({
         .longName = "keep-going",
         .shortName ='k',
         .description = "keep going after a build fails",
-        .handler = {&(bool&) settings.keepGoing, true},
+        .handler = {&(bool&) settings()->keepGoing, true},
     });
 
     addFlag({
         .longName = "fallback",
         .description = "build from source if substitution fails",
-        .handler = {&(bool&) settings.tryFallback, true},
+        .handler = {&(bool&) settings()->tryFallback, true},
     });
 
     auto intSettingAlias = [&](char shortName, const std::string & longName,
         const std::string & description, const std::string & dest) {
         mkFlag<unsigned int>(shortName, longName, description, [=](unsigned int n) {
-            settings.set(dest, std::to_string(n));
+            settings()->set(dest, std::to_string(n));
         });
     };
 
@@ -217,7 +217,7 @@ LegacyArgs::LegacyArgs(const std::string & programName,
     intSettingAlias(0, "timeout", "number of seconds before a build is killed", "timeout");
 
     mkFlag(0, "readonly-mode", "do not write to the Nix store",
-        &settings.readOnlyMode);
+        &settings()->readOnlyMode);
 
     mkFlag(0, "no-gc-warning", "disable warning about not using '--add-root'",
         &gcWarning, false);
@@ -226,7 +226,7 @@ LegacyArgs::LegacyArgs(const std::string & programName,
         .longName = "store",
         .description = "URI of the Nix store to use",
         .labels = {"store-uri"},
-        .handler = {&(std::string&) settings.storeUri},
+        .handler = {&(std::string&) settings()->storeUri},
     });
 }
 
@@ -277,15 +277,15 @@ void printVersion(const string & programName)
 #if HAVE_SODIUM
         cfg.push_back("signed-caches");
 #endif
-        std::cout << "System type: " << settings.thisSystem << "\n";
-        std::cout << "Additional system types: " << concatStringsSep(", ", settings.extraPlatforms.get()) << "\n";
+        std::cout << "System type: " << settings()->thisSystem << "\n";
+        std::cout << "Additional system types: " << concatStringsSep(", ", settings()->extraPlatforms.get()) << "\n";
         std::cout << "Features: " << concatStringsSep(", ", cfg) << "\n";
-        std::cout << "System configuration file: " << settings.nixConfDir + "/nix.conf" << "\n";
+        std::cout << "System configuration file: " << settings()->nixConfDir + "/nix.conf" << "\n";
         std::cout << "User configuration files: " <<
-            concatStringsSep(":", settings.nixUserConfFiles)
+            concatStringsSep(":", settings()->nixUserConfFiles)
             << "\n";
-        std::cout << "Store directory: " << settings.nixStore << "\n";
-        std::cout << "State directory: " << settings.nixStateDir << "\n";
+        std::cout << "Store directory: " << settings()->nixStore << "\n";
+        std::cout << "State directory: " << settings()->nixStateDir << "\n";
     }
     throw Exit();
 }
@@ -294,7 +294,7 @@ void printVersion(const string & programName)
 void showManPage(const string & name)
 {
     restoreSignals();
-    setenv("MANPATH", settings.nixManDir.c_str(), 1);
+    setenv("MANPATH", settings()->nixManDir.c_str(), 1);
     execlp("man", "man", name.c_str(), nullptr);
     throw SysError("command 'man %1%' failed", name.c_str());
 }
@@ -403,3 +403,5 @@ PrintFreed::~PrintFreed()
 Exit::~Exit() { }
 
 }
+
+