Merge pull request #13008 from Mic92/aliases

Move alias support from NixArgs to MultiCommand + test

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);