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Add optional support (#3303)
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@ -508,6 +508,7 @@ Standard Library Types Formatting
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* `std::thread::id <https://en.cppreference.com/w/cpp/thread/thread/id>`_
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* `std::monostate <https://en.cppreference.com/w/cpp/utility/variant/monostate>`_
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* `std::variant <https://en.cppreference.com/w/cpp/utility/variant/variant>`_
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* `std::optional <https://en.cppreference.com/w/cpp/utility/optional>`_
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Formatting Variants
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-------------------
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@ -29,6 +29,9 @@
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# if FMT_HAS_INCLUDE(<variant>)
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# include <variant>
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# endif
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# if FMT_HAS_INCLUDE(<optional>)
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# include <optional>
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# endif
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#endif
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// GCC 4 does not support FMT_HAS_INCLUDE.
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@ -91,6 +94,49 @@ template <typename Char>
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struct formatter<std::thread::id, Char> : basic_ostream_formatter<Char> {};
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FMT_END_NAMESPACE
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#ifdef __cpp_lib_optional
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FMT_BEGIN_NAMESPACE
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template <typename T, typename Char>
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struct formatter<std::optional<T>, Char,
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std::enable_if_t<is_formattable<T, Char>::value>> {
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private:
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formatter<T, Char> underlying_;
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static constexpr basic_string_view<Char> optional =
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detail::string_literal<Char, 'o', 'p', 't', 'i', 'o', 'n', 'a', 'l',
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'('>{};
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static constexpr basic_string_view<Char> none =
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detail::string_literal<Char, 'n', 'o', 'n', 'e'>{};
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template <class U>
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FMT_CONSTEXPR static auto maybe_set_debug_format(U& u, bool set)
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-> decltype(u.set_debug_format(set)) {
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u.set_debug_format(set);
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}
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template <class U>
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FMT_CONSTEXPR static void maybe_set_debug_format(U&, ...) {}
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public:
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template <typename ParseContext> FMT_CONSTEXPR auto parse(ParseContext& ctx) {
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maybe_set_debug_format(underlying_, true);
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return underlying_.parse(ctx);
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}
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template <typename FormatContext>
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auto format(std::optional<T> const& opt, FormatContext& ctx) const
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-> decltype(ctx.out()) {
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if (!opt) return detail::write<Char>(ctx.out(), none);
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auto out = ctx.out();
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out = detail::write<Char>(out, optional);
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ctx.advance_to(out);
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out = underlying_.format(*opt, ctx);
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return detail::write(out, ')');
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}
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};
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FMT_END_NAMESPACE
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#endif // __cpp_lib_optional
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#ifdef __cpp_lib_variant
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FMT_BEGIN_NAMESPACE
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template <typename Char> struct formatter<std::monostate, Char> {
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@ -50,6 +50,34 @@ TEST(std_test, thread_id) {
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EXPECT_FALSE(fmt::format("{}", std::this_thread::get_id()).empty());
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}
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TEST(std_test, optional) {
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#ifdef __cpp_lib_optional
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EXPECT_EQ(fmt::format("{}", std::optional<int>{}), "none");
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EXPECT_EQ(fmt::format("{}", std::pair{1, "second"}), "(1, \"second\")");
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EXPECT_EQ(fmt::format("{}", std::vector{std::optional{1}, std::optional{2},
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std::optional{3}}),
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"[optional(1), optional(2), optional(3)]");
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EXPECT_EQ(
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fmt::format("{}", std::optional<std::optional<const char*>>{{"nested"}}),
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"optional(optional(\"nested\"))");
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EXPECT_EQ(
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fmt::format("{:<{}}", std::optional{std::string{"left aligned"}}, 30),
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"optional(\"left aligned\" )");
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EXPECT_EQ(
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fmt::format("{::d}", std::optional{std::vector{'h', 'e', 'l', 'l', 'o'}}),
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"optional([104, 101, 108, 108, 111])");
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EXPECT_EQ(fmt::format("{}", std::optional{std::string{"string"}}),
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"optional(\"string\")");
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EXPECT_EQ(fmt::format("{}", std::optional{'C'}), "optional(\'C\')");
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EXPECT_EQ(fmt::format("{:.{}f}", std::optional{3.14}, 1), "optional(3.1)");
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struct unformattable {};
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EXPECT_FALSE((fmt::is_formattable<unformattable>::value));
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EXPECT_FALSE((fmt::is_formattable<std::optional<unformattable>>::value));
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EXPECT_TRUE((fmt::is_formattable<std::optional<int>>::value));
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#endif
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}
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TEST(std_test, variant) {
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#ifdef __cpp_lib_variant
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EXPECT_EQ(fmt::format("{}", std::monostate{}), "monostate");
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@ -16,6 +16,7 @@
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#include "fmt/color.h"
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#include "fmt/ostream.h"
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#include "fmt/ranges.h"
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#include "fmt/std.h"
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#include "gtest-extra.h" // Contains
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#include "util.h" // get_locale
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@ -588,4 +589,12 @@ TEST(locale_test, sign) {
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EXPECT_EQ(fmt::format(std::locale(), L"{:L}", -50), L"-50");
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}
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TEST(std_test_xchar, optional) {
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# ifdef __cpp_lib_optional
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EXPECT_EQ(fmt::format(L"{}", std::optional{L'C'}), L"optional(\'C\')");
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EXPECT_EQ(fmt::format(L"{}", std::optional{std::wstring{L"wide string"}}),
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L"optional(\"wide string\")");
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# endif
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}
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#endif // FMT_STATIC_THOUSANDS_SEPARATOR
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