[FEATURE] Enum support for the argument parser.

include/seqan3/argument_parser/argument_parser.hpp

@@ -28,6 +28,7 @@
 #include <seqan3/argument_parser/detail/format_parse.hpp>
 #include <seqan3/argument_parser/detail/version_check.hpp>
 #include <seqan3/core/char_operations/predicate.hpp>
+#include <seqan3/core/detail/debug_stream_string_convertible.hpp>
 #include <seqan3/core/detail/terminal.hpp>
 #include <seqan3/core/detail/to_string.hpp>
 #include <seqan3/io/stream/concept.hpp>
@@ -229,8 +230,8 @@ class argument_parser
      */
     template <typename option_type, validator validator_type = detail::default_validator<option_type>>
     //!\cond
-        requires (input_stream_over<std::istringstream, option_type> ||
-                  input_stream_over<std::istringstream, typename option_type::value_type>) &&
+        requires (argument_parser_compatible_option<option_type> ||
+                  argument_parser_compatible_option<typename option_type::value_type>) &&
                   std::invocable<validator_type, option_type>
     //!\endcond
     void add_option(option_type & value,
@@ -291,8 +292,8 @@ class argument_parser
      */
     template <typename option_type, validator validator_type = detail::default_validator<option_type>>
     //!\cond
-        requires (input_stream_over<std::istringstream, option_type> ||
-                  input_stream_over<std::istringstream, typename option_type::value_type>) &&
+        requires (argument_parser_compatible_option<option_type> ||
+                  argument_parser_compatible_option<typename option_type::value_type>) &&
                   std::invocable<validator_type, option_type>
     //!\endcond
     void add_positional_option(option_type & value,

include/seqan3/argument_parser/auxiliary.hpp

@@ -15,12 +15,160 @@
 #include <sstream>
 #include <vector>
 
+#include <seqan3/core/detail/customisation_point.hpp>
 #include <seqan3/core/detail/debug_stream_type.hpp>
+#include <seqan3/core/type_traits/basic.hpp>
 #include <seqan3/io/stream/concept.hpp>
+#include <seqan3/std/concepts>
+
+namespace seqan3::custom
+{
+
+/*!\brief A type that can be specialised to provide customisation point implementations so that third party types
+ *        model the seqan3::string_convertible concept.
+ * \tparam t The type you wish to specialise for.
+ * \ingroup argument_parser
+ *
+ * \details
+ *
+ * You can specialise a class like this:
+ *
+ * \include test/snippet/argument_parser/string_convertible.cpp
+ *
+ * Please note that by default the `t const`, `t &` and `t const &` specialisations of this class inherit the
+ * specialisation for `t` so you usually only need to provide a specialisation for `t`.
+ *
+ * \note Only use this if you cannot provide respective functions in your namespace.
+ */
+template <typename t>
+struct string_convertibility
+{}; // forward
+
+//!\cond
+template <typename t>
+struct string_convertibility<t const> : string_convertibility<t>
+{};
+
+template <typename t>
+struct string_convertibility<t &> : string_convertibility<t>
+{};
+
+template <typename t>
+struct string_convertibility<t const &> : string_convertibility<t>
+{};
+//!\endcond
+
+} // seqan3::custom
+
+namespace seqan3::detail::adl_only
+{
+
+//!\brief Poison-pill overload to prevent non-ADL forms of unqualified lookup.
+template <typename t>
+std::unordered_map<std::string, t> string_conversion_map(t v) = delete;
+
+//!\brief Functor definition for seqan3::string_conversion_map.
+struct string_conversion_map_fn
+{
+private:
+    SEQAN3_CPO_IMPL(2, seqan3::custom::string_convertibility<decltype(v)>::string_conversion_map(v)) // explicit custom.
+    SEQAN3_CPO_IMPL(1, string_conversion_map(v))                 // ADL
+    SEQAN3_CPO_IMPL(0, v.string_conversion_map())                // member
+
+public:
+    //!\brief Operator definition.
+    template <typename option_type>
+    //!\cond
+        requires requires (option_type const a)
+        {
+            { impl(priority_tag<2>{}, a) };
+        }
+    //!\endcond
+    constexpr auto operator()(option_type const a) const noexcept
+    {
+        return impl(priority_tag<2>{}, a);
+    }
+};
+
+} // namespace seqan3::detail::adl_only
 
 namespace seqan3
 {
 
+/*!\name Customisation Points
+ * \{
+ */
+
+/*!\brief Return a conversion map from std::string to option_type.
+ * \tparam your_type Type of the value to retrieve the conversion map for.
+ * \param value The value is not used, just its type.
+ * \returns A std::unordered_map<std::string, your_type> that maps a string identifier to a value of your_type.
+ * \ingroup argument_parser
+ * \details
+ *
+ * This is a function object. Invoke it with the parameter(s) specified above.
+ *
+ * It acts as a wrapper and looks for three possible implementations (in this order):
+ *
+ *   1. A static member function `string_conversion_map(your_type const a)` in
+ *      `seqan3::custom::string_convertibility<your_type>`.
+ *   2. A free function `string_conversion_map(your_type const a)` in the namespace of your type (or as `friend`).
+ *   3. A member function called `string_conversion_map()`.
+ *
+ * ### Example
+ *
+ * If you are working on a type in your own namespace, you should implement a free function like this:
+ *
+ * \include test/snippet/argument_parser/string_conversion_map.cpp
+ *
+ * **Only if you cannot access the namespace of your type to customize** you may specialize
+ * the seqan3::custom::string_convertibility struct like this:
+ *
+ * \include test/snippet/argument_parser/string_convertible.cpp
+ *
+ * ### Customisation point
+ *
+ * This is a customisation point (see \ref about_customisation). To specify the behaviour for your own type,
+ * simply provide one of the three functions specified above.
+ */
+inline constexpr auto string_conversion_map = detail::adl_only::string_conversion_map_fn{};
+//!\}
+
+/*!\interface seqan3::string_convertible <>
+ * \brief Checks whether the free function seqan3::string_conversion_map can be called on the type.
+ * \ingroup argument_parser
+ * \tparam option_type The type to check.
+ *
+ * ### Requirements
+ *
+ * * The free function seqan3::string_conversion_map must be defined on a value of the type and return
+ *   a `std::unordered_map<std::string, option_type>`.
+ */
+//!\cond
+template <typename option_type>
+SEQAN3_CONCEPT string_convertible = requires
+{
+    { seqan3::string_conversion_map(option_type{}) } -> std::unordered_map<std::string, option_type>;
+};
+//!\endcond
+
+/*!\interface seqan3::argument_parser_compatible_option <>
+ * \brief Checks whether the the type can be used in an add_(positional_)option call on the argument parser.
+ * \ingroup argument_parser
+ * \tparam option_type The type to check.
+ *
+ * ### Requirements
+ *
+ * In order to model this concept, the type must either define the `operator>>` over std::string stream or
+ * a free function seqan3::string_conversion_map must be defined on a value of the type and return
+ * a `std::unordered_map<std::string, option_type>`.
+ */
+//!\cond
+template <typename option_type>
+SEQAN3_CONCEPT argument_parser_compatible_option = input_stream_over<std::istringstream, option_type> ||
+                                                   string_convertible<option_type>;
+//!\endcond
+
 /*!\brief Used to further specify argument_parser options/flags.
  * \ingroup argument_parser
  *

include/seqan3/argument_parser/detail/format_base.hpp

@@ -24,6 +24,8 @@
 #include <seqan3/argument_parser/exceptions.hpp>
 #include <seqan3/argument_parser/validators.hpp>
 #include <seqan3/core/detail/reflection.hpp>
+#include <seqan3/range/views/get.hpp>
+#include <seqan3/range/views/view_all.hpp>
 #include <seqan3/std/filesystem>
 
 namespace seqan3::detail
@@ -233,17 +235,25 @@ class format_help_base : public format_base
      * \param[in]  long_id   The long identifier for the option (e.g. "integer").
      * \param[in]  desc      The description of the option.
      * \param[in]  spec      Advanced option specification, see seqan3::option_spec.
-     * \param[in]  validator The validator applied to the value after parsing (callable).
+     * \param[in]  val       The validator applied to the value after parsing (callable).
      */
     template <typename option_type, typename validator_type>
     void add_option(option_type & value,
                     char const short_id,
                     std::string const & long_id,
                     std::string const & desc,
                     option_spec const & spec,
-                    validator_type && validator)
+                    validator_type && val)
     {
-        parser_set_up_calls.push_back([this, &value, short_id, long_id, desc, spec, validator] ()
+        std::string msg = val.get_help_page_message();
+
+        if constexpr (string_convertible<option_type>)
+        {
+            auto table = seqan3::string_conversion_map(value);
+            msg = (val | value_list_validator<option_type>{(views::all(table) | views::get<1>)}).get_help_page_message();
+        }
+
+        parser_set_up_calls.push_back([this, &value, short_id, long_id, desc, spec, msg] ()
         {
             if (!(spec & option_spec::HIDDEN) && (!(spec & option_spec::ADVANCED) || show_advanced_options))
                   derived_t().print_list_item(prep_id_for_help(short_id, long_id) +
@@ -252,7 +262,7 @@ class format_help_base : public format_base
                                               ((spec & option_spec::REQUIRED)
                                                   ? std::string{" "}
                                                   : detail::to_string(" Default: ", value, ". ")) +
-                                              validator.get_help_page_message());
+                                              msg);
         });
     }
 
@@ -283,14 +293,22 @@ class format_help_base : public format_base
      *
      * \param[out] value     The variable in which to store the given command line argument.
      * \param[in]  desc      The description of the positional option.
-     * \param[in]  validator The validator applied to the value after parsing (callable).
+     * \param[in]  val       The validator applied to the value after parsing (callable).
      */
     template <typename option_type, typename validator_type>
     void add_positional_option(option_type & value,
                                std::string const & desc,
-                               validator_type & validator)
+                               validator_type & val)
     {
-        positional_option_calls.push_back([this, &value, desc, validator] ()
+        std::string msg = val.get_help_page_message();
+
+        if constexpr (string_convertible<option_type>)
+        {
+            auto table = seqan3::string_conversion_map(value);
+            msg = (val | value_list_validator<option_type>{(views::all(table) | views::get<1>)}).get_help_page_message();
+        }
+
+        positional_option_calls.push_back([this, &value, desc, msg] ()
         {
             ++positional_option_count;
             derived_t().print_list_item(detail::to_string("\\fBARGUMENT-", positional_option_count, "\\fP ",
@@ -300,7 +318,7 @@ class format_help_base : public format_base
                                         ((sequence_container<option_type> && !std::same_as<option_type, std::string>)
                                             ? detail::to_string(" Default: ", value, ". ")
                                             : std::string{" "}) +
-                                        validator.get_help_page_message());
+                                        msg);
         });
     }
 

include/seqan3/argument_parser/detail/format_parse.hpp

@@ -283,13 +283,11 @@ class format_parse : public format_base
     }
 
     /*!\brief Tries to cast an input string into a value.
-     *
-     * \tparam option_t Must satisfy the seqan3::input_stream_over.
-     *
+     * \tparam option_t Must model seqan3::input_stream_over.
      * \param[out] value Stores the casted value.
      * \param[in]  in    The input argument to be casted.
      *
-     * \throws seqan3::parser_invalid_argument
+     * \throws seqan3::type_conversion_failed
      */
     template <typename option_t>
     //!\cond
@@ -305,6 +303,33 @@ class format_parse : public format_base
                                          get_type_name_as_string(value) + ".");
     }
 
+    /*!\brief Tries to cast an input string into a value.
+     * \tparam option_t Must model seqan3::string_convertible.
+     * \param[out] value Stores the cast value.
+     * \param[in]  in    The input argument to be cast.
+     *
+     * \throws seqan3::type_conversion_failed
+     */
+    template <typename option_t>
+    //!\cond
+        requires string_convertible<option_t>
+    //!\endcond
+    void retrieve_value(option_t & value, std::string const & in)
+    {
+        std::string tmp;
+        std::istringstream is{in};
+        is >> tmp;
+
+        auto map = seqan3::string_conversion_map(value);
+        auto it = map.find(tmp);
+
+        if (it == map.end())
+            throw type_conversion_failed("Argument " + in + " could not be cast to enum type " +
+                                         get_display_name_v<option_t>.str() + ".");
+        else
+            value = it->second;
+    }
+
     //!\cond
     void retrieve_value(std::string & value, std::string const & in)
     {

include/seqan3/core/debug_stream.hpp

@@ -15,6 +15,7 @@
 #include <seqan3/core/detail/debug_stream_alphabet.hpp>
 #include <seqan3/core/detail/debug_stream_optional.hpp>
 #include <seqan3/core/detail/debug_stream_range.hpp>
+#include <seqan3/core/detail/debug_stream_string_convertible.hpp>
 #include <seqan3/core/detail/debug_stream_tuple.hpp>
 #include <seqan3/core/detail/debug_stream_type.hpp>
 #include <seqan3/core/detail/debug_stream_variant.hpp>

include/seqan3/core/detail/debug_stream_string_convertible.hpp

@@ -0,0 +1,52 @@
+// -----------------------------------------------------------------------------------------------------
+// Copyright (c) 2006-2019, Knut Reinert & Freie Universität Berlin
+// Copyright (c) 2016-2019, Knut Reinert & MPI für molekulare Genetik
+// This file may be used, modified and/or redistributed under the terms of the 3-clause BSD-License
+// shipped with this file and also available at: https://github.com/seqan/seqan3/blob/master/LICENSE.md
+// -----------------------------------------------------------------------------------------------------
+
+/*!\file
+ * \author Svenja Mehringer <svenja.mehringer AT fu-berlin.de>
+ * \brief Provides an overload for the seqan3::debug_stream if a seqan3::string_conversion_map of the type exists.
+ */
+
+#pragma once
+
+#include <variant>
+
+#include <seqan3/argument_parser/auxiliary.hpp>
+#include <seqan3/core/detail/debug_stream_type.hpp>
+
+namespace seqan3
+{
+/*!\name Formatted output overloads
+ * \{
+ */
+/*!\brief A type (e.g. an enum) can be made debug streamable by customizing the seqan3::string_conversion_map.
+ * \tparam option_type Type of the enum to be printed.
+ * \param s  The seqan3::debug_stream.
+ * \param op The value to print.
+ * \relates seqan3::debug_stream_type
+ *
+ * \details
+ *
+ * This searches the seqan3::string_conversion_map of the respective type for the value \p op and prints the
+ * respective string if found or '\<UNKNOWN_VALUE\>' if the value cannot be found in the map.
+ */
+template <typename char_t, typename option_type>
+//!\cond
+    requires string_convertible<remove_cvref_t<option_type>>
+//!\endcond
+inline debug_stream_type<char_t> & operator<<(debug_stream_type<char_t> & s, option_type && op)
+{
+    for (auto & [key, value] : string_conversion_map(op))
+    {
+        if (op == value)
+            return s << key;
+    }
+
+    return s << "<UNKNOWN_VALUE>";
+}
+//!\}
+
+} // namespace seqan3