Add support for @answer-files

.gitignore

@@ -31,7 +31,10 @@
 *.out
 *.app
 
-build
-build-*
-*-build-*
-.idea
+/build
+/build-*
+/*-build-*
+/.idea
+/.vscode
+
+web.log

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required (VERSION 3.12)
 project (args
-  VERSION 0.11.0
+  VERSION 0.12.0
   DESCRIPTION ""
   LANGUAGES CXX)
 

README.md

@@ -5,7 +5,7 @@
 
 Small open-source library for program argument parser, inspired by Python's `argparse`, depending only on the standard library, with C++17 as minimum requirement.
 
-It automatically builds and prints out help info for program arguments, can react to missing or unrecognized arguments and has support for arguments with and without values.
+It automatically builds and prints out help info for program arguments, can react to missing or unrecognized arguments and has support for arguments with and without values. It can also support placing long lists of arguments into an [@answer-file](#parseruse_answer_file).
 
 The argument values can be stored in:
 - `std::string`s,
@@ -129,8 +129,6 @@ Short arguments can also be glued together, except that any argument with a valu
 -czfvalue
 ```
 
-
-
 # Classes
 
 ## args::arglist
@@ -180,6 +178,7 @@ Produces built in translations for given string ids:
 |`needed_enum_known_values`|`"known values for $arg1: $arg2"`|
 |`required`|`"argument $arg1 is required"`|
 |`error_msg`|`"$arg1: error: $arg2"`|
+|`file_not_found`|`"cannot open $arg1"`|
 
 ## args::enum_traits<Enum>
 
@@ -376,11 +375,46 @@ Parses the arguments. The `on_unknown` instructs the parser, how to react on an
 
 The `maybe_width` is a hint for terminal width. If missing, will try to get the current width of a terminal. If the program is not attached to terminal, will print the messages without any formatting.
 
+### parser::use_answer_file
+
+```cxx
+void use_answer_file(char marker = '@');
+bool uses_answer_file() const noexcept;
+char answer_file_marker() const noexcept;
+```
+
+Turns on/off support for answer files in argument list. By default, `marker` is set to 0, which turns the support off.
+
+```c++
+assert(!parser.uses_answer_file());
+parser.use_answer_file();
+assert(parser.uses_answer_file());
+```
+
+When turned on, will use the marker character to recognize the name of the answer file and use further arguments from there. For instance, if a program decides to support answer files and file named `options` contains this text:
+
+```
+-vv
+-v
+--arg1=value1
+--arg2
+value2
+--arg3=value3
+--arg4
+```
+
+Then those calls are equivalent:
+
+```
+$ ./prog -vvv --arg1 value1 --arg2 value2 --arg3=value3 --arg4
+$ ./prog @options
+```
+
 ### parser::provide_help
 
 ```cxx
-void provide_help(bool value = true);
-bool provide_help() const noexcept;
+void provide_help(bool value);
+bool provides_help() const noexcept;
 ```
 
 Turns off/on the built in support for `"-h"` and `"--help"` arguments.

include/args/parser.hpp

@@ -86,6 +86,7 @@ namespace args {
 		std::string prog_;
 		std::string usage_;
 		bool provide_help_ = true;
+		char answer_file_marker_{};
 		std::optional<size_t> parse_width_ = {};
 		base_translator const* tr_;
 		[[nodiscard]] std::string _(lng id,
@@ -96,14 +97,16 @@ namespace args {
 
 		[[nodiscard]] std::pair<size_t, size_t> count_args() const noexcept;
 
-		bool parse_long(std::string_view const& name,
-		                unsigned& i,
-		                unknown_action on_unknown);
-		bool parse_short(std::string_view const& name,
-		                 unsigned& i,
-		                 unknown_action on_unknown);
-		bool parse_positional(std::string_view const& value,
+		template <typename ArgList>
+		bool parse_list(ArgList& list, unknown_action on_unknown);
+		template <typename ArgList>
+		bool parse_long(ArgList& list, unknown_action on_unknown);
+		template <typename ArgList>
+		bool parse_short(ArgList& list, unknown_action on_unknown);
+		bool parse_positional(std::string const& value,
 		                      unknown_action on_unknown);
+		bool parse_answer_file(std::string const& value,
+		                       unknown_action on_unknown);
 
 		template <typename Action, typename... Args>
 		actions::builder add(Args&&... args) {
@@ -190,7 +193,15 @@ namespace args {
 		std::string const& usage() const noexcept;
 
 		void provide_help(bool value = true) { provide_help_ = value; }
-		bool provide_help() const noexcept { return provide_help_; }
+		bool provides_help() const noexcept { return provide_help_; }
+
+		void use_answer_file(char marker = '@') {
+			answer_file_marker_ = marker;
+		}
+		bool uses_answer_file() const noexcept {
+			return answer_file_marker_ != 0;
+		}
+		char answer_file_marker() const noexcept { return answer_file_marker_; }
 
 		arglist const& args() const noexcept { return args_; }
 

include/args/translator.hpp

@@ -21,7 +21,8 @@ namespace args {
 		needed_enum_unknown,
 		needed_enum_known_values,
 		required,
-		error_msg
+		error_msg,
+		file_not_found
 	};
 
 	struct base_translator {