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Add format_as support for std::variant and std::expected formatters (#4575)

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Signed-off-by: Vladislav Shchapov <vladislav@shchapov.ru>
This commit is contained in:
Vladislav Shchapov
2025-10-19 02:05:21 +05:00
committed by GitHub
parent 378a5ab3c1
commit 85f6ecc7a0
4 changed files with 66 additions and 24 deletions
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46
test/std-test.cc
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@@ -197,7 +197,33 @@ class my_class {
return fmt::to_string(elm.av);
}
};
class my_class_int {
public:
int av;
private:
friend auto format_as(const my_class_int& elm) -> int { return elm.av; }
};
} // namespace my_nso
TEST(std_test, expected_format_as) {
#ifdef __cpp_lib_expected
EXPECT_EQ(
fmt::format(
"{}", std::expected<my_nso::my_number, int>{my_nso::my_number::one}),
"expected(\"first\")");
EXPECT_EQ(
fmt::format("{}",
std::expected<my_nso::my_class, int>{my_nso::my_class{7}}),
"expected(\"7\")");
EXPECT_EQ(fmt::format("{}",
std::expected<my_nso::my_class_int, int>{
my_nso::my_class_int{8}}),
"expected(8)");
#endif
}
TEST(std_test, optional_format_as) {
#ifdef __cpp_lib_optional
EXPECT_EQ(fmt::format("{}", std::optional<my_nso::my_number>{}), "none");
@@ -206,6 +232,8 @@ TEST(std_test, optional_format_as) {
EXPECT_EQ(fmt::format("{}", std::optional<my_nso::my_class>{}), "none");
EXPECT_EQ(fmt::format("{}", std::optional{my_nso::my_class{7}}),
"optional(\"7\")");
EXPECT_EQ(fmt::format("{}", std::optional{my_nso::my_class_int{8}}),
"optional(8)");
#endif
}
@@ -275,6 +303,24 @@ TEST(std_test, variant) {
#endif
}
TEST(std_test, variant_format_as) {
#ifdef __cpp_lib_variant
EXPECT_EQ(fmt::format("{}", std::variant<my_nso::my_number>{}),
"variant(\"first\")");
EXPECT_EQ(fmt::format(
"{}", std::variant<my_nso::my_number>{my_nso::my_number::one}),
"variant(\"first\")");
EXPECT_EQ(
fmt::format("{}", std::variant<my_nso::my_class>{my_nso::my_class{7}}),
"variant(\"7\")");
EXPECT_EQ(
fmt::format("{}",
std::variant<my_nso::my_class_int>{my_nso::my_class_int{8}}),
"variant(8)");
#endif
}
TEST(std_test, error_code) {
auto& generic = std::generic_category();
EXPECT_EQ(fmt::format("{}", std::error_code(42, generic)), "generic:42");