Move alias support from NixArgs to MultiCommand

This allows subcommands to declare aliases, e.g. `nix store ping` is
now a proper alias of `nix store info`.

doc/manual/meson.build

@@ -281,7 +281,6 @@ nix3_manpages = [
   'nix3-store',
   'nix3-store-optimise',
   'nix3-store-path-from-hash-part',
-  'nix3-store-ping',
   'nix3-store-prefetch-file',
   'nix3-store-repair',
   'nix3-store-sign',

src/libutil/args.cc

@@ -647,4 +647,25 @@ nlohmann::json MultiCommand::toJSON()
     return res;
 }
 
+Strings::iterator MultiCommand::rewriteArgs(Strings & args, Strings::iterator pos)
+{
+    if (command)
+        return command->second->rewriteArgs(args, pos);
+
+    if (aliasUsed || pos == args.end()) return pos;
+    auto arg = *pos;
+    auto i = aliases.find(arg);
+    if (i == aliases.end()) return pos;
+    auto & info = i->second;
+    if (info.status == AliasStatus::Deprecated) {
+        warn("'%s' is a deprecated alias for '%s'",
+            arg, concatStringsSep(" ", info.replacement));
+    }
+    pos = args.erase(pos);
+    for (auto j = info.replacement.rbegin(); j != info.replacement.rend(); ++j)
+        pos = args.insert(pos, *j);
+    aliasUsed = true;
+    return pos;
+}
+
 }

src/libutil/include/nix/util/args.hh

@@ -393,8 +393,30 @@ public:
 
     nlohmann::json toJSON() override;
 
+    enum struct AliasStatus {
+        /** Aliases that don't go away */
+        AcceptedShorthand,
+        /** Aliases that will go away */
+        Deprecated,
+    };
+
+    /** An alias, except for the original syntax, which is in the map key. */
+    struct AliasInfo {
+        AliasStatus status;
+        std::vector<std::string> replacement;
+    };
+
+    /**
+     * A list of aliases (remapping a deprecated/shorthand subcommand
+     * to something else).
+     */
+    std::map<std::string, AliasInfo> aliases;
+
+    Strings::iterator rewriteArgs(Strings & args, Strings::iterator pos) override;
+
 protected:
     std::string commandName = "";
+    bool aliasUsed = false;
 };
 
 Strings argvToStrings(int argc, char * * argv);

src/nix/main.cc

@@ -50,19 +50,6 @@ void chrootHelper(int argc, char * * argv);
 
 namespace nix {
 
-enum struct AliasStatus {
-    /** Aliases that don't go away */
-    AcceptedShorthand,
-    /** Aliases that will go away */
-    Deprecated,
-};
-
-/** An alias, except for the original syntax, which is in the map key. */
-struct AliasInfo {
-    AliasStatus status;
-    std::vector<std::string> replacement;
-};
-
 /* Check if we have a non-loopback/link-local network interface. */
 static bool haveInternet()
 {
@@ -153,9 +140,8 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs, virtual RootArgs
             .handler = {[&]() { refresh = true; }},
             .experimentalFeature = Xp::NixCommand,
         });
-    }
 
-    std::map<std::string, AliasInfo> aliases = {
+        aliases = {
             {"add-to-store", { AliasStatus::Deprecated, {"store", "add-path"}}},
             {"cat-nar", { AliasStatus::Deprecated, {"nar", "cat"}}},
             {"cat-store", { AliasStatus::Deprecated, {"store", "cat"}}},
@@ -180,26 +166,7 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs, virtual RootArgs
             {"verify", { AliasStatus::Deprecated, {"store", "verify"}}},
             {"doctor", { AliasStatus::Deprecated, {"config", "check"}}},
         };
-
+    };
-    bool aliasUsed = false;
-
-    Strings::iterator rewriteArgs(Strings & args, Strings::iterator pos) override
-    {
-        if (aliasUsed || command || pos == args.end()) return pos;
-        auto arg = *pos;
-        auto i = aliases.find(arg);
-        if (i == aliases.end()) return pos;
-        auto & info = i->second;
-        if (info.status == AliasStatus::Deprecated) {
-            warn("'%s' is a deprecated alias for '%s'",
-                arg, concatStringsSep(" ", info.replacement));
-        }
-        pos = args.erase(pos);
-        for (auto j = info.replacement.rbegin(); j != info.replacement.rend(); ++j)
-            pos = args.insert(pos, *j);
-        aliasUsed = true;
-        return pos;
-    }
 
     std::string description() override
     {

src/nix/store-info.cc

@@ -7,7 +7,7 @@
 
 using namespace nix;
 
-struct CmdPingStore : StoreCommand, MixJSON
+struct CmdInfoStore : StoreCommand, MixJSON
 {
     std::string description() override
     {
@@ -46,15 +46,4 @@ struct CmdPingStore : StoreCommand, MixJSON
     }
 };
 
-struct CmdInfoStore : CmdPingStore
+static auto rCmdInfoStore = registerCommand2<CmdInfoStore>({"store", "info"});
-{
-    void run(nix::ref<nix::Store> store) override
-    {
-        warn("'nix store ping' is a deprecated alias for 'nix store info'");
-        CmdPingStore::run(store);
-    }
-};
-
-
-static auto rCmdPingStore = registerCommand2<CmdPingStore>({"store", "info"});
-static auto rCmdInfoStore = registerCommand2<CmdInfoStore>({"store", "ping"});

src/nix/store.cc

@@ -5,7 +5,11 @@ using namespace nix;
 struct CmdStore : NixMultiCommand
 {
     CmdStore() : NixMultiCommand("store", RegisterCommand::getCommandsFor({"store"}))
-    { }
+    {
+        aliases = {
+            {"ping", { AliasStatus::Deprecated, {"info"}}},
+        };
+    }
 
     std::string description() override
     {