Make subcommand construction in MultiCommand lazy

(cherry picked from commit a0de58f471)

src/libutil/args.cc

@@ -215,17 +215,15 @@ void Command::printHelp(const string & programName, std::ostream & out)
     }
 }
 
-MultiCommand::MultiCommand(const std::vector<ref<Command>> & _commands)
+MultiCommand::MultiCommand(const Commands & commands)
+    : commands(commands)
 {
-    for (auto & command : _commands)
-        commands.emplace(command->name(), command);
-
     expectedArgs.push_back(ExpectedArg{"command", 1, true, [=](std::vector<std::string> ss) {
         assert(!command);
         auto i = commands.find(ss[0]);
         if (i == commands.end())
             throw UsageError("'%s' is not a recognised command", ss[0]);
-        command = i->second;
+        command = i->second();
     }});
 }
 
@@ -246,10 +244,11 @@ void MultiCommand::printHelp(const string & programName, std::ostream & out)
     out << "Available commands:\n";
 
     Table2 table;
-    for (auto & command : commands) {
+    for (auto & i : commands) {
-        auto descr = command.second->description();
+        auto command = i.second();
+        auto descr = command->description();
         if (!descr.empty())
-            table.push_back(std::make_pair(command.second->name(), descr));
+            table.push_back(std::make_pair(command->name(), descr));
     }
     printTable(out, table);
 }

src/libutil/args.hh

@@ -192,8 +192,15 @@ public:
    run() method. */
 struct Command : virtual Args
 {
+private:
+    std::string _name;
+
+public:
+
     virtual ~Command() { }
-    virtual std::string name() = 0;
+
+    std::string name() { return _name; }
+
     virtual void prepare() { };
     virtual void run() = 0;
 
@@ -210,7 +217,7 @@ struct Command : virtual Args
     void printHelp(const string & programName, std::ostream & out) override;
 };
 
-typedef std::map<std::string, ref<Command>> Commands;
+typedef std::map<std::string, std::function<ref<Command>()>> Commands;
 
 /* An argument parser that supports multiple subcommands,
    i.e. ‘<command> <subcommand>’. */
@@ -221,7 +228,7 @@ public:
 
     std::shared_ptr<Command> command;
 
-    MultiCommand(const std::vector<ref<Command>> & commands);
+    MultiCommand(const Commands & commands);
 
     void printHelp(const string & programName, std::ostream & out) override;
 

src/nix/add-to-store.cc

@@ -22,11 +22,6 @@ struct CmdAddToStore : MixDryRun, StoreCommand
             .dest(&namePart);
     }
 
-    std::string name() override
-    {
-        return "add-to-store";
-    }
-
     std::string description() override
     {
         return "add a path to the Nix store";
@@ -58,4 +53,4 @@ struct CmdAddToStore : MixDryRun, StoreCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdAddToStore>());
+static auto r1 = registerCommand<CmdAddToStore>("add-to-store");

src/nix/build.cc

@@ -24,11 +24,6 @@ struct CmdBuild : MixDryRun, InstallablesCommand
             .set(&outLink, Path(""));
     }
 
-    std::string name() override
-    {
-        return "build";
-    }
-
     std::string description() override
     {
         return "build a derivation or fetch a store path";
@@ -69,4 +64,4 @@ struct CmdBuild : MixDryRun, InstallablesCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdBuild>());
+static auto r1 = registerCommand<CmdBuild>("build");

src/nix/cat.cc

@@ -28,11 +28,6 @@ struct CmdCatStore : StoreCommand, MixCat
         expectArg("path", &path);
     }
 
-    std::string name() override
-    {
-        return "cat-store";
-    }
-
     std::string description() override
     {
         return "print the contents of a store file on stdout";
@@ -54,11 +49,6 @@ struct CmdCatNar : StoreCommand, MixCat
         expectArg("path", &path);
     }
 
-    std::string name() override
-    {
-        return "cat-nar";
-    }
-
     std::string description() override
     {
         return "print the contents of a file inside a NAR file";
@@ -70,5 +60,5 @@ struct CmdCatNar : StoreCommand, MixCat
     }
 };
 
-static RegisterCommand r1(make_ref<CmdCatStore>());
+static auto r1 = registerCommand<CmdCatStore>("cat-store");
-static RegisterCommand r2(make_ref<CmdCatNar>());
+static auto r2 = registerCommand<CmdCatNar>("cat-nar");

src/nix/command.cc

@@ -5,7 +5,7 @@
 
 namespace nix {
 
-std::vector<ref<Command>> * RegisterCommand::commands = 0;
+Commands * RegisterCommand::commands = nullptr;
 
 StoreCommand::StoreCommand()
 {

src/nix/command.hh

@@ -151,15 +151,22 @@ struct StorePathCommand : public InstallablesCommand
 /* A helper class for registering commands globally. */
 struct RegisterCommand
 {
-    static std::vector<ref<Command>> * commands;
+    static Commands * commands;
 
-    RegisterCommand(ref<Command> command)
+    RegisterCommand(const std::string & name,
+        std::function<ref<Command>()> command)
     {
-        if (!commands) commands = new std::vector<ref<Command>>;
+        if (!commands) commands = new Commands;
-        commands->push_back(command);
+        commands->emplace(name, command);
     }
 };
 
+template<class T>
+static RegisterCommand registerCommand(const std::string & name)
+{
+    return RegisterCommand(name, [](){ return make_ref<T>(); });
+}
+
 std::shared_ptr<Installable> parseInstallable(
     SourceExprCommand & cmd, ref<Store> store, const std::string & installable,
     bool useDefaultInstallables);

src/nix/copy.cc

@@ -42,11 +42,6 @@ struct CmdCopy : StorePathsCommand
             .set(&substitute, Substitute);
     }
 
-    std::string name() override
-    {
-        return "copy";
-    }
-
     std::string description() override
     {
         return "copy paths between Nix stores";
@@ -97,4 +92,4 @@ struct CmdCopy : StorePathsCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdCopy>());
+static auto r1 = registerCommand<CmdCopy>("copy");

src/nix/doctor.cc

@@ -38,11 +38,6 @@ struct CmdDoctor : StoreCommand
 {
     bool success = true;
 
-    std::string name() override
-    {
-        return "doctor";
-    }
-
     std::string description() override
     {
         return "check your system for potential problems and print a PASS or FAIL for each check.";
@@ -136,4 +131,4 @@ struct CmdDoctor : StoreCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdDoctor>());
+static auto r1 = registerCommand<CmdDoctor>("doctore");

src/nix/dump-path.cc

@@ -5,11 +5,6 @@ using namespace nix;
 
 struct CmdDumpPath : StorePathCommand
 {
-    std::string name() override
-    {
-        return "dump-path";
-    }
-
     std::string description() override
     {
         return "dump a store path to stdout (in NAR format)";
@@ -33,4 +28,4 @@ struct CmdDumpPath : StorePathCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdDumpPath>());
+static auto r1 = registerCommand<CmdDumpPath>("dump-path");

src/nix/edit.cc

@@ -10,11 +10,6 @@ using namespace nix;
 
 struct CmdEdit : InstallableCommand
 {
-    std::string name() override
-    {
-        return "edit";
-    }
-
     std::string description() override
     {
         return "open the Nix expression of a Nix package in $EDITOR";
@@ -50,4 +45,4 @@ struct CmdEdit : InstallableCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdEdit>());
+static auto r1 = registerCommand<CmdEdit>("edit");

src/nix/eval.cc

@@ -18,11 +18,6 @@ struct CmdEval : MixJSON, InstallableCommand
         mkFlag(0, "raw", "print strings unquoted", &raw);
     }
 
-    std::string name() override
-    {
-        return "eval";
-    }
-
     std::string description() override
     {
         return "evaluate a Nix expression";
@@ -74,4 +69,4 @@ struct CmdEval : MixJSON, InstallableCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdEval>());
+static auto r1 = registerCommand<CmdEval>("eval");

src/nix/hash.cc

@@ -36,11 +36,6 @@ struct CmdHash : Command
         expectArgs("paths", &paths);
     }
 
-    std::string name() override
-    {
-        return mode == mFile ? "hash-file" : "hash-path";
-    }
-
     std::string description() override
     {
         return mode == mFile
@@ -71,8 +66,8 @@ struct CmdHash : Command
     }
 };
 
-static RegisterCommand r1(make_ref<CmdHash>(CmdHash::mFile));
+static RegisterCommand r1("hash-file", [](){ return make_ref<CmdHash>(CmdHash::mFile); });
-static RegisterCommand r2(make_ref<CmdHash>(CmdHash::mPath));
+static RegisterCommand r2("hash-path", [](){ return make_ref<CmdHash>(CmdHash::mPath); });
 
 struct CmdToBase : Command
 {
@@ -88,15 +83,6 @@ struct CmdToBase : Command
         expectArgs("strings", &args);
     }
 
-    std::string name() override
-    {
-        return
-            base == Base16 ? "to-base16" :
-            base == Base32 ? "to-base32" :
-            base == Base64 ? "to-base64" :
-            "to-sri";
-    }
-
     std::string description() override
     {
         return fmt("convert a hash to %s representation",
@@ -113,10 +99,10 @@ struct CmdToBase : Command
     }
 };
 
-static RegisterCommand r3(make_ref<CmdToBase>(Base16));
+static RegisterCommand r3("to-base16", [](){ return make_ref<CmdToBase>(Base16); });
-static RegisterCommand r4(make_ref<CmdToBase>(Base32));
+static RegisterCommand r4("to-base32", [](){ return make_ref<CmdToBase>(Base32); });
-static RegisterCommand r5(make_ref<CmdToBase>(Base64));
+static RegisterCommand r5("to-base64", [](){ return make_ref<CmdToBase>(Base64); });
-static RegisterCommand r6(make_ref<CmdToBase>(SRI));
+static RegisterCommand r6("to-sri", [](){ return make_ref<CmdToBase>(SRI); });
 
 /* Legacy nix-hash command. */
 static int compatNixHash(int argc, char * * argv)

src/nix/log.cc

@@ -8,15 +8,6 @@ using namespace nix;
 
 struct CmdLog : InstallableCommand
 {
-    CmdLog()
-    {
-    }
-
-    std::string name() override
-    {
-        return "log";
-    }
-
     std::string description() override
     {
         return "show the build log of the specified packages or paths, if available";
@@ -68,4 +59,4 @@ struct CmdLog : InstallableCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdLog>());
+static auto r1 = registerCommand<CmdLog>("log");

src/nix/ls.cc

@@ -100,11 +100,6 @@ struct CmdLsStore : StoreCommand, MixLs
         };
     }
 
-    std::string name() override
-    {
-        return "ls-store";
-    }
-
     std::string description() override
     {
         return "show information about a store path";
@@ -136,11 +131,6 @@ struct CmdLsNar : Command, MixLs
         };
     }
 
-    std::string name() override
-    {
-        return "ls-nar";
-    }
-
     std::string description() override
     {
         return "show information about the contents of a NAR file";
@@ -152,5 +142,5 @@ struct CmdLsNar : Command, MixLs
     }
 };
 
-static RegisterCommand r1(make_ref<CmdLsStore>());
+static auto r1 = registerCommand<CmdLsStore>("ls-store");
-static RegisterCommand r2(make_ref<CmdLsNar>());
+static auto r2 = registerCommand<CmdLsNar>("ls-nar");

src/nix/make-content-addressable.cc

@@ -11,11 +11,6 @@ struct CmdMakeContentAddressable : StorePathsCommand
         realiseMode = Build;
     }
 
-    std::string name() override
-    {
-        return "make-content-addressable";
-    }
-
     std::string description() override
     {
         return "rewrite a path or closure to content-addressable form";
@@ -92,4 +87,4 @@ struct CmdMakeContentAddressable : StorePathsCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdMakeContentAddressable>());
+static auto r1 = registerCommand<CmdMakeContentAddressable>("make-content-addressable");

src/nix/optimise-store.cc

@@ -8,15 +8,6 @@ using namespace nix;
 
 struct CmdOptimiseStore : StoreCommand
 {
-    CmdOptimiseStore()
-    {
-    }
-
-    std::string name() override
-    {
-        return "optimise-store";
-    }
-
     std::string description() override
     {
         return "replace identical files in the store by hard links";
@@ -38,4 +29,4 @@ struct CmdOptimiseStore : StoreCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdOptimiseStore>());
+static auto r1 = registerCommand<CmdOptimiseStore>("optimise-store");

src/nix/path-info.cc

@@ -24,11 +24,6 @@ struct CmdPathInfo : StorePathsCommand, MixJSON
         mkFlag(0, "sigs", "show signatures", &showSigs);
     }
 
-    std::string name() override
-    {
-        return "path-info";
-    }
-
     std::string description() override
     {
         return "query information about store paths";
@@ -130,4 +125,4 @@ struct CmdPathInfo : StorePathsCommand, MixJSON
     }
 };
 
-static RegisterCommand r1(make_ref<CmdPathInfo>());
+static auto r1 = registerCommand<CmdPathInfo>("path-info");

src/nix/ping-store.cc

@@ -6,11 +6,6 @@ using namespace nix;
 
 struct CmdPingStore : StoreCommand
 {
-    std::string name() override
-    {
-        return "ping-store";
-    }
-
     std::string description() override
     {
         return "test whether a store can be opened";
@@ -32,4 +27,4 @@ struct CmdPingStore : StoreCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdPingStore>());
+static auto r1 = registerCommand<CmdPingStore>("ping-store");

src/nix/repl.cc

@@ -801,8 +801,6 @@ struct CmdRepl : StoreCommand, MixEvalArgs
         expectArgs("files", &files);
     }
 
-    std::string name() override { return "repl"; }
-
     std::string description() override
     {
         return "start an interactive environment for evaluating Nix expressions";
@@ -816,6 +814,6 @@ struct CmdRepl : StoreCommand, MixEvalArgs
     }
 };
 
-static RegisterCommand r1(make_ref<CmdRepl>());
+static auto r1 = registerCommand<CmdRepl>("repl");
 
 }

src/nix/run.cc

@@ -61,11 +61,6 @@ struct CmdRun : InstallablesCommand
             .handler([&](std::vector<std::string> ss) { unset.insert(ss.front()); });
     }
 
-    std::string name() override
-    {
-        return "run";
-    }
-
     std::string description() override
     {
         return "run a shell in which the specified packages are available";
@@ -182,7 +177,7 @@ struct CmdRun : InstallablesCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdRun>());
+static auto r1 = registerCommand<CmdRun>("run");
 
 void chrootHelper(int argc, char * * argv)
 {

src/nix/search.cc

@@ -52,11 +52,6 @@ struct CmdSearch : SourceExprCommand, MixJSON
             .handler([&]() { writeCache = false; useCache = false; });
     }
 
-    std::string name() override
-    {
-        return "search";
-    }
-
     std::string description() override
     {
         return "query available packages";
@@ -277,4 +272,4 @@ struct CmdSearch : SourceExprCommand, MixJSON
     }
 };
 
-static RegisterCommand r1(make_ref<CmdSearch>());
+static auto r1 = registerCommand<CmdSearch>("search");

src/nix/show-config.cc

@@ -8,15 +8,6 @@ using namespace nix;
 
 struct CmdShowConfig : Command, MixJSON
 {
-    CmdShowConfig()
-    {
-    }
-
-    std::string name() override
-    {
-        return "show-config";
-    }
-
     std::string description() override
     {
         return "show the Nix configuration";
@@ -37,4 +28,4 @@ struct CmdShowConfig : Command, MixJSON
     }
 };
 
-static RegisterCommand r1(make_ref<CmdShowConfig>());
+static auto r1 = registerCommand<CmdShowConfig>("show-config");

src/nix/show-derivation.cc

@@ -22,11 +22,6 @@ struct CmdShowDerivation : InstallablesCommand
             .set(&recursive, true);
     }
 
-    std::string name() override
-    {
-        return "show-derivation";
-    }
-
     std::string description() override
     {
         return "show the contents of a store derivation";
@@ -116,4 +111,4 @@ struct CmdShowDerivation : InstallablesCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdShowDerivation>());
+static auto r1 = registerCommand<CmdShowDerivation>("show-derivation");

src/nix/sigs.cc

@@ -22,11 +22,6 @@ struct CmdCopySigs : StorePathsCommand
             .handler([&](std::vector<std::string> ss) { substituterUris.push_back(ss[0]); });
     }
 
-    std::string name() override
-    {
-        return "copy-sigs";
-    }
-
     std::string description() override
     {
         return "copy path signatures from substituters (like binary caches)";
@@ -93,7 +88,7 @@ struct CmdCopySigs : StorePathsCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdCopySigs>());
+static auto r1 = registerCommand<CmdCopySigs>("copy-sigs");
 
 struct CmdSignPaths : StorePathsCommand
 {
@@ -109,11 +104,6 @@ struct CmdSignPaths : StorePathsCommand
             .dest(&secretKeyFile);
     }
 
-    std::string name() override
-    {
-        return "sign-paths";
-    }
-
     std::string description() override
     {
         return "sign the specified paths";
@@ -146,4 +136,4 @@ struct CmdSignPaths : StorePathsCommand
     }
 };
 
-static RegisterCommand r3(make_ref<CmdSignPaths>());
+static auto r2 = registerCommand<CmdSignPaths>("sign-paths");

src/nix/upgrade-nix.cc

@@ -30,11 +30,6 @@ struct CmdUpgradeNix : MixDryRun, StoreCommand
             .dest(&storePathsUrl);
     }
 
-    std::string name() override
-    {
-        return "upgrade-nix";
-    }
-
     std::string description() override
     {
         return "upgrade Nix to the latest stable version";
@@ -157,4 +152,4 @@ struct CmdUpgradeNix : MixDryRun, StoreCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdUpgradeNix>());
+static auto r1 = registerCommand<CmdUpgradeNix>("upgrade-nix");

src/nix/verify.cc

@@ -30,11 +30,6 @@ struct CmdVerify : StorePathsCommand
         mkIntFlag('n', "sigs-needed", "require that each path has at least N valid signatures", &sigsNeeded);
     }
 
-    std::string name() override
-    {
-        return "verify";
-    }
-
     std::string description() override
     {
         return "verify the integrity of store paths";
@@ -180,4 +175,4 @@ struct CmdVerify : StorePathsCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdVerify>());
+static auto r1 = registerCommand<CmdVerify>("verify");

src/nix/why-depends.cc

@@ -44,11 +44,6 @@ struct CmdWhyDepends : SourceExprCommand
             .set(&all, true);
     }
 
-    std::string name() override
-    {
-        return "why-depends";
-    }
-
     std::string description() override
     {
         return "show why a package has another package in its closure";
@@ -264,4 +259,4 @@ struct CmdWhyDepends : SourceExprCommand
     }
 };
 
-static RegisterCommand r1(make_ref<CmdWhyDepends>());
+static auto r1 = registerCommand<CmdWhyDepends>("why-depends");