libos: Allow ArgumentParser users to specify they want leftover arguments

apps/cat.cpp

@@ -24,16 +24,18 @@ static Result<void> do_cat(StringView path)
 Result<int> luna_main(int argc, char** argv)
 {
     StringView filename;
+    Vector<StringView> files;
 
     os::ArgumentParser parser;
     parser.add_description("Concatenate files to standard output."_sv);
     parser.add_system_program_info("cat"_sv);
     parser.add_positional_argument(filename, "file"_sv, "-"_sv);
-    Vector<StringView> extra_files = TRY(parser.parse(argc, argv));
+    parser.set_vector_argument(files);
+    parser.parse(argc, argv);
 
     TRY(do_cat(filename));
 
-    for (auto file : extra_files) TRY(do_cat(file));
+    for (auto file : files) TRY(do_cat(file));
 
     return 0;
 }

libos/include/os/ArgumentParser.h

@@ -21,7 +21,9 @@ namespace os
         Result<void> add_value_argument(StringView& out, char short_flag, StringView long_flag, StringView fallback,
                                         StringView help = {});
 
-        Result<Vector<StringView>> parse(int argc, char* const* argv);
+        void set_vector_argument(Vector<StringView>& out, bool allow_no_more_flags = false);
+
+        Result<void> parse(int argc, char* const* argv);
 
         struct ProgramInfo
         {
@@ -74,6 +76,8 @@ namespace os
         Vector<PositionalArgument> m_positional_args;
         Vector<SwitchArgument> m_switch_args;
         Vector<ValueArgument> m_value_args;
+        Vector<StringView>* m_vector_argument { nullptr };
+        bool m_allow_no_more_flags_after_vector_argument_start { false };
         ProgramInfo m_program_info;
         StringView m_description = {};
         bool m_add_short_help_flag { false };

libos/src/ArgumentParser.cpp

@@ -68,6 +68,13 @@ namespace os
         return m_value_args.try_append(move(arg));
     }
 
+    void ArgumentParser::set_vector_argument(Vector<StringView>& out, bool allow_no_more_flags)
+    {
+        m_vector_argument = &out;
+        m_allow_no_more_flags_after_vector_argument_start = allow_no_more_flags;
+        return;
+    }
+
     constexpr auto copyright_text = "Copyright (C) 2023, the Luna authors.";
     constexpr auto license_text = "Licensed under the BSD-2 license <https://opensource.org/license/bsd-2-clause/>";
 
@@ -104,12 +111,10 @@ namespace os
         return arg.length() > 2 && arg[0] == '-' && arg[1] == '-';
     }
 
-    Result<Vector<StringView>> ArgumentParser::parse(int argc, char* const* argv)
+    Result<void> ArgumentParser::parse(int argc, char* const* argv)
     {
         StringView program_name = argv[0];
 
-        Vector<StringView> leftovers;
-
         Option<ValueArgument> current_value_argument = {};
         bool is_parsing_value_argument = false;
 
@@ -225,7 +230,11 @@ namespace os
             Option<PositionalArgument> current = m_positional_args.try_dequeue();
             if (!current.has_value())
             {
-                TRY(leftovers.try_append(arg));
+                if (m_vector_argument)
+                {
+                    TRY(m_vector_argument->try_append(arg));
+                    if (m_allow_no_more_flags_after_vector_argument_start) is_still_parsing_flags = false;
+                }
                 continue;
             }
 
@@ -254,7 +263,7 @@ namespace os
             else { *arg.out = arg.fallback; }
         }
 
-        return leftovers;
+        return {};
     }
 
     Result<void> ArgumentParser::usage(StringView program_name)
@@ -268,6 +277,8 @@ namespace os
             else { TRY(sb.format(" [%s]", arg.name.chars())); }
         }
 
+        if (m_vector_argument) sb.format("%s..."_sv, m_positional_args.size() ? "" : " ");
+
         TRY(sb.add('\n'));
 
         auto usage_line = TRY(sb.string());