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add support for statically named arguments with FMT_STRING

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This commit is contained in:
Alexey Ochapov 2021-05-13 03:57:07 +03:00 committed by Victor Zverovich
parent ea94d6d93c
commit 54f22a3eef
4 changed files with 67 additions and 31 deletions
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16
include/fmt/compile.h
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@ -191,24 +191,10 @@ constexpr const auto& get([[maybe_unused]] const T& first,
return get<N - 1>(rest...);
}
constexpr int invalid_arg_index = -1;
template <int N, typename T, typename... Args, typename Char>
constexpr int get_arg_index_by_name(basic_string_view<Char> name) {
if constexpr (detail::is_statically_named_arg<T>()) {
if (name == T::name) return N;
}
if constexpr (sizeof...(Args) == 0) {
return invalid_arg_index;
} else {
return get_arg_index_by_name<N + 1, Args...>(name);
}
}
template <typename Char, typename... Args>
constexpr int get_arg_index_by_name(basic_string_view<Char> name,
type_list<Args...>) {
return get_arg_index_by_name<0, Args...>(name);
return get_arg_index_by_name<Args...>(name);
}
template <int N, typename> struct get_type_impl;

52
include/fmt/core.h
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@ -281,6 +281,16 @@
# define FMT_COMPILE_TIME_CHECKS 0
#endif
#ifndef FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
# if defined(__cpp_nontype_template_args) && \
((FMT_GCC_VERSION >= 903 && __cplusplus >= 201709L) || \
__cpp_nontype_template_args >= 201911L)
# define FMT_USE_NONTYPE_TEMPLATE_PARAMETERS 1
# else
# define FMT_USE_NONTYPE_TEMPLATE_PARAMETERS 0
# endif
#endif
// Enable minimal optimizations for more compact code in debug mode.
FMT_GCC_PRAGMA("GCC push_options")
#ifndef __OPTIMIZE__
@ -991,6 +1001,7 @@ template <typename Char>
inline void init_named_args(named_arg_info<Char>*, int, int) {}
template <typename T> struct is_named_arg : std::false_type {};
template <typename T> struct is_statically_named_arg : std::false_type {};
template <typename T, typename Char>
struct is_named_arg<named_arg<Char, T>> : std::true_type {};
@ -2425,6 +2436,36 @@ class compile_parse_context
using base::check_arg_id;
};
constexpr int invalid_arg_index = -1;
#if FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
template <int N, typename T, typename... Args, typename Char>
constexpr int get_arg_index_by_name(basic_string_view<Char> name) {
if constexpr (detail::is_statically_named_arg<T>()) {
if (name == T::name) return N;
}
if constexpr (sizeof...(Args) == 0) {
return invalid_arg_index;
} else {
return get_arg_index_by_name<N + 1, Args...>(name);
}
}
template <typename... Args, typename Char>
constexpr int get_arg_index_by_name(basic_string_view<Char> name) {
if constexpr (sizeof...(Args) == 0) {
return invalid_arg_index;
} else {
return get_arg_index_by_name<0, Args...>(name);
}
}
#else
template <typename... Args, typename Char>
constexpr int get_arg_index_by_name(basic_string_view<Char>) {
return invalid_arg_index;
}
#endif
template <typename Char, typename ErrorHandler, typename... Args>
class format_string_checker {
public:
@ -2437,9 +2478,16 @@ class format_string_checker {
FMT_CONSTEXPR int on_arg_id() { return context_.next_arg_id(); }
FMT_CONSTEXPR int on_arg_id(int id) { return context_.check_arg_id(id), id; }
FMT_CONSTEXPR int on_arg_id(basic_string_view<Char>) {
on_error("compile-time checks don't support named arguments");
FMT_CONSTEXPR int on_arg_id(basic_string_view<Char> id) {
#if FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
auto index = get_arg_index_by_name<Args...>(id);
if (index == invalid_arg_index) on_error("named argument is not found");
return context_.check_arg_id(index), index;
#else
(void)id;
on_error("compile-time checks for named arguments require C++20 support");
return 0;
#endif
}
FMT_CONSTEXPR void on_replacement_field(int, const Char*) {}

13
include/fmt/format.h
View File

@ -255,16 +255,6 @@ inline int ctzll(uint64_t x) {
FMT_END_NAMESPACE
#endif
#ifndef FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
# if defined(__cpp_nontype_template_args) && \
((FMT_GCC_VERSION >= 903 && __cplusplus >= 201709L) || \
__cpp_nontype_template_args >= 201911L)
# define FMT_USE_NONTYPE_TEMPLATE_PARAMETERS 1
# else
# define FMT_USE_NONTYPE_TEMPLATE_PARAMETERS 0
# endif
#endif
FMT_BEGIN_NAMESPACE
namespace detail {
@ -3226,9 +3216,6 @@ template <typename Char> struct udl_formatter {
}
};
template <typename T, typename = void>
struct is_statically_named_arg : std::false_type {};
# if FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
template <typename T, typename Char, size_t N, fixed_string<Char, N> Str>
struct statically_named_arg : view {

17
test/format-test.cc
View File

@ -1694,6 +1694,14 @@ TEST(format_test, compile_time_string) {
EXPECT_EQ(L"42", fmt::format(FMT_STRING(L"{}"), 42));
EXPECT_EQ("foo", fmt::format(FMT_STRING("{}"), string_like()));
#if FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
using namespace fmt::literals;
EXPECT_EQ("foobar", fmt::format(FMT_STRING("{foo}{bar}"), "bar"_a = "bar",
"foo"_a = "foo"));
EXPECT_EQ("", fmt::format(FMT_STRING("")));
EXPECT_EQ("", fmt::format(FMT_STRING(""), "arg"_a = 42));
#endif
(void)static_with_null;
(void)static_with_null_wide;
(void)static_no_null;
@ -2339,8 +2347,15 @@ TEST(format_test, format_string_errors) {
# else
fmt::print("warning: constexpr is broken in this version of MSVC\n");
# endif
EXPECT_ERROR("{foo", "compile-time checks don't support named arguments",
# if FMT_USE_NONTYPE_TEMPLATE_PARAMETERS
EXPECT_ERROR("{foo}", "named argument is not found", decltype("bar"_a = 42));
EXPECT_ERROR("{foo}", "named argument is not found",
decltype(fmt::arg("foo", 42)));
# else
EXPECT_ERROR("{foo}",
"compile-time checks for named arguments require C++20 support",
int);
# endif
EXPECT_ERROR_NOARGS("{10000000000}", "number is too big");
EXPECT_ERROR_NOARGS("{0x}", "invalid format string");
EXPECT_ERROR_NOARGS("{-}", "invalid format string");