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fix: support optional<T> with format_as(T) (#3712) #3713

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merged 1 commit into from
Nov 16, 2023
Merged

fix: support optional<T> with format_as(T) (#3712) #3713

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1 change: 1 addition & 0 deletions include/fmt/format.h
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Original file line number Diff line number Diff line change
Expand Up @@ -4053,6 +4053,7 @@ struct formatter<T, Char, enable_if_t<detail::has_format_as<T>::value>>
: private formatter<detail::format_as_t<T>, Char> {
using base = formatter<detail::format_as_t<T>, Char>;
using base::parse;
using base::set_debug_format;

template <typename FormatContext>
auto format(const T& value, FormatContext& ctx) const -> decltype(ctx.out()) {
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30 changes: 30 additions & 0 deletions test/std-test.cc
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Expand Up @@ -90,6 +90,36 @@ TEST(std_test, optional) {
#endif
}

namespace my_nso {
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What does "nso" stand for?

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What does "nso" stand for?

I was trying to follow the naming scheme with short namespaces below, my_ns1 & my_ns2, and added an o for optional, since my_ns3 before the two others didn't make sense. But I'll change to whatever you prefer.

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my_nso is OK

enum class my_number {
one,
two,
};
auto format_as(my_number number) -> fmt::string_view {
return number == my_number::one ? "first" : "second";
}

class my_class {
public:
int av;

private:
friend auto format_as(const my_class& elm) -> std::string {
return fmt::to_string(elm.av);
}
};
} // namespace my_nso
TEST(std_test, optional_format_as) {
#ifdef __cpp_lib_optional
EXPECT_EQ(fmt::format("{}", std::optional<my_nso::my_number>{}), "none");
EXPECT_EQ(fmt::format("{}", std::optional{my_nso::my_number::one}),
"optional(\"first\")");
EXPECT_EQ(fmt::format("{}", std::optional<my_nso::my_class>{}), "none");
EXPECT_EQ(fmt::format("{}", std::optional{my_nso::my_class{7}}),
"optional(\"7\")");
#endif
}

struct throws_on_move {
throws_on_move() = default;

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