Cleanup

src/libutil/args.cc

@@ -86,7 +86,7 @@ void Args::printHelp(const string & programName, std::ostream & out)
     for (auto & exp : expectedArgs) {
         std::cout << renderLabels({exp.label});
         // FIXME: handle arity > 1
-        if (exp.arity == 0) std::cout << "...";
+        if (exp.handler.arity == ArityAny) std::cout << "...";
         if (exp.optional) std::cout << "?";
     }
     std::cout << "\n";
@@ -127,8 +127,8 @@ bool Args::processFlag(Strings::iterator & pos, Strings::iterator end)
                 if (flag.handler.arity == ArityAny) break;
                 throw UsageError("flag '%s' requires %d argument(s)", name, flag.handler.arity);
             }
-            if (auto prefix = needsCompletion(*pos))
             if (flag.completer)
+                if (auto prefix = needsCompletion(*pos))
                     flag.completer(n, *prefix);
             args.push_back(*pos++);
         }
@@ -179,12 +179,17 @@ bool Args::processArgs(const Strings & args, bool finish)
 
     bool res = false;
 
-    if ((exp.arity == 0 && finish) ||
-        (exp.arity > 0 && args.size() == exp.arity))
+    if ((exp.handler.arity == ArityAny && finish) ||
+        (exp.handler.arity != ArityAny && args.size() == exp.handler.arity))
     {
         std::vector<std::string> ss;
-        for (auto & s : args) ss.push_back(s);
-        exp.handler(std::move(ss));
+        for (const auto &[n, s] : enumerate(args)) {
+            ss.push_back(s);
+            if (exp.completer)
+                if (auto prefix = needsCompletion(s))
+                    exp.completer(n, *prefix);
+        }
+        exp.handler.fun(ss);
         expectedArgs.pop_front();
         res = true;
     }
@@ -214,45 +219,16 @@ Args::Flag Args::Flag::mkHashTypeFlag(std::string && longName, HashType * ht)
     };
 }
 
-void completePath(size_t, std::string_view s)
+void completePath(size_t, std::string_view prefix)
 {
-    if (auto prefix = needsCompletion(s)) {
     pathCompletions = true;
     glob_t globbuf;
-        if (glob((*prefix + "*").c_str(), GLOB_NOESCAPE | GLOB_TILDE, nullptr, &globbuf) == 0) {
+    if (glob((std::string(prefix) + "*").c_str(), GLOB_NOESCAPE | GLOB_TILDE, nullptr, &globbuf) == 0) {
         for (size_t i = 0; i < globbuf.gl_pathc; ++i)
             completions->insert(globbuf.gl_pathv[i]);
         globfree(&globbuf);
     }
 }
-}
-
-void Args::expectPathArg(const std::string & label, string * dest, bool optional)
-{
-    expectedArgs.push_back({
-        .label = label,
-        .arity = 1,
-        .optional = optional,
-        .handler = {[=](std::vector<std::string> ss) {
-            completePath(0, ss[0]);
-            *dest = ss[0];
-        }}
-    });
-}
-
-void Args::expectPathArgs(const std::string & label, std::vector<std::string> * dest)
-{
-    expectedArgs.push_back({
-        .label = label,
-        .arity = 0,
-        .optional = false,
-        .handler = {[=](std::vector<std::string> ss) {
-            for (auto & s : ss)
-                completePath(0, s);
-            *dest = std::move(ss);
-        }}
-    });
-}
 
 Strings argvToStrings(int argc, char * * argv)
 {
@@ -301,18 +277,22 @@ void Command::printHelp(const string & programName, std::ostream & out)
 MultiCommand::MultiCommand(const Commands & commands)
     : commands(commands)
 {
-    expectedArgs.push_back(ExpectedArg{"command", 1, true, [=](std::vector<std::string> ss) {
+    expectArgs({
+        .label = "command",
+        .optional = true,
+        .handler = {[=](std::string s) {
             assert(!command);
-        if (auto prefix = needsCompletion(ss[0])) {
+            if (auto prefix = needsCompletion(s)) {
                 for (auto & [name, command] : commands)
                     if (hasPrefix(name, *prefix))
                         completions->insert(name);
             }
-        auto i = commands.find(ss[0]);
+            auto i = commands.find(s);
             if (i == commands.end())
-            throw UsageError("'%s' is not a recognised command", ss[0]);
-        command = {ss[0], i->second()};
-    }});
+                throw UsageError("'%s' is not a recognised command", s);
+            command = {s, i->second()};
+        }}
+    });
 
     categories[Command::catDefault] = "Available commands";
 }

src/libutil/args.hh

@@ -28,11 +28,6 @@ protected:
 
     static const size_t ArityAny = std::numeric_limits<size_t>::max();
 
-    /* Flags. */
-    struct Flag
-    {
-        typedef std::shared_ptr<Flag> ptr;
-
     struct Handler
     {
         std::function<void(std::vector<std::string>)> fun;
@@ -64,6 +59,11 @@ protected:
             , arity(2)
         { }
 
+        Handler(std::vector<std::string> * dest)
+            : fun([=](std::vector<std::string> ss) { *dest = ss; })
+            , arity(ArityAny)
+        { }
+
         template<class T>
         Handler(T * dest)
             : fun([=](std::vector<std::string> ss) { *dest = ss[0]; })
@@ -77,6 +77,11 @@ protected:
         { }
     };
 
+    /* Flags. */
+    struct Flag
+    {
+        typedef std::shared_ptr<Flag> ptr;
+
         std::string longName;
         char shortName = 0;
         std::string description;
@@ -99,9 +104,9 @@ protected:
     struct ExpectedArg
     {
         std::string label;
-        size_t arity = 0; // 0 = any
         bool optional = false;
-        std::function<void(std::vector<std::string>)> handler;
+        Handler handler;
+        std::function<void(size_t, std::string_view)> completer;
     };
 
     std::list<ExpectedArg> expectedArgs;
@@ -175,26 +180,30 @@ public:
         });
     }
 
+    void expectArgs(ExpectedArg && arg)
+    {
+        expectedArgs.emplace_back(std::move(arg));
+    }
+
     /* Expect a string argument. */
     void expectArg(const std::string & label, string * dest, bool optional = false)
     {
-        expectedArgs.push_back(ExpectedArg{label, 1, optional, [=](std::vector<std::string> ss) {
-            *dest = ss[0];
-        }});
+        expectArgs({
+            .label = label,
+            .optional = true,
+            .handler = {dest}
+        });
     }
 
-    void expectPathArg(const std::string & label, string * dest, bool optional = false);
-
     /* Expect 0 or more arguments. */
     void expectArgs(const std::string & label, std::vector<std::string> * dest)
     {
-        expectedArgs.push_back(ExpectedArg{label, 0, false, [=](std::vector<std::string> ss) {
-            *dest = std::move(ss);
-        }});
+        expectArgs({
+            .label = label,
+            .handler = {dest}
+        });
     }
 
-    void expectPathArgs(const std::string & label, std::vector<std::string> * dest);
-
     friend class MultiCommand;
 };
 
@@ -266,6 +275,6 @@ extern bool pathCompletions;
 
 std::optional<std::string> needsCompletion(std::string_view s);
 
-void completePath(size_t, std::string_view s);
+void completePath(size_t, std::string_view prefix);
 
 }

src/nix/cat.cc

@@ -25,7 +25,11 @@ struct CmdCatStore : StoreCommand, MixCat
 {
     CmdCatStore()
     {
-        expectPathArg("path", &path);
+        expectArgs({
+            .label = "path",
+            .handler = {&path},
+            .completer = completePath
+        });
     }
 
     std::string description() override
@@ -47,7 +51,11 @@ struct CmdCatNar : StoreCommand, MixCat
 
     CmdCatNar()
     {
-        expectPathArg("nar", &narPath);
+        expectArgs({
+            .label = "nar",
+            .handler = {&narPath},
+            .completer = completePath
+        });
         expectArg("path", &path);
     }
 

src/nix/command.hh

@@ -73,10 +73,7 @@ struct InstallablesCommand : virtual Args, SourceExprCommand
 {
     std::vector<std::shared_ptr<Installable>> installables;
 
-    InstallablesCommand()
-    {
-        expectArgs("installables", &_installables);
-    }
+    InstallablesCommand();
 
     void prepare() override;
 

src/nix/hash.cc

@@ -31,7 +31,11 @@ struct CmdHash : Command
             .labels({"modulus"})
             .dest(&modulus);
         #endif
-        expectPathArgs("paths", &paths);
+        expectArgs({
+            .label = "paths",
+            .handler = {&paths},
+            .completer = completePath
+        });
     }
 
     std::string description() override

src/nix/installables.cc

@@ -571,6 +571,14 @@ StorePathSet toDerivations(ref<Store> store,
     return drvPaths;
 }
 
+InstallablesCommand::InstallablesCommand()
+{
+    expectArgs({
+        .label = "installables",
+        .handler = {&_installables},
+    });
+}
+
 void InstallablesCommand::prepare()
 {
     if (_installables.empty() && useDefaultInstallables())

src/nix/ls.cc

@@ -85,7 +85,11 @@ struct CmdLsStore : StoreCommand, MixLs
 {
     CmdLsStore()
     {
-        expectPathArg("path", &path);
+        expectArgs({
+            .label = "path",
+            .handler = {&path},
+            .completer = completePath
+        });
     }
 
     Examples examples() override
@@ -117,7 +121,11 @@ struct CmdLsNar : Command, MixLs
 
     CmdLsNar()
     {
-        expectPathArg("nar", &narPath);
+        expectArgs({
+            .label = "nar",
+            .handler = {&narPath},
+            .completer = completePath
+        });
         expectArg("path", &path);
     }
 

src/nix/repl.cc

@@ -767,7 +767,11 @@ struct CmdRepl : StoreCommand, MixEvalArgs
 
     CmdRepl()
     {
-        expectPathArgs("files", &files);
+        expectArgs({
+            .label = "files",
+            .handler = {&files},
+            .completer = completePath
+        });
     }
 
     std::string description() override

src/nix/run.cc

@@ -149,7 +149,11 @@ struct CmdRun : InstallableCommand, RunCommon
 
     CmdRun()
     {
-        expectPathArgs("args", &args);
+        expectArgs({
+            .label = "args",
+            .handler = {&args},
+            .completer = completePath
+        });
     }
 
     std::string description() override