%j doesn't seem to work with a duration object

[yannou38]

here is the snippet : https://godbolt.org/z/jTxGzvEhT

I'm trying to format a duration in days:hours:minutes:seconds.
using %T work wonders for hours:minutes:seconds, however %j does not compile at all, despite the docs saying "If the type being formatted is a specialization of duration, the decimal number of days without padding." which should fill my use case.

here is a snippet of my compilation error:

[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/chrono.h: In member function 'void DemoWindow::acquisitionFinished()':
[build] C:\Projets\CB110_DATA_LOGGER_SW\UI\demowindow.cpp:124:53:   in 'constexpr' expansion of 'fmt::v10::basic_format_string<char, std::chrono::duration<long long int, std::ratio<1, 1> >&>("{:%j}")'
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/core.h:2740:40:   in 'constexpr' expansion of 'fmt::v10::detail::parse_format_string<true, char, format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > > >(((fmt::v10::basic_format_string<char, std::chrono::duration<long long int, std::ratio<1, 1> >&>*)this)->fmt::v10::basic_format_string<char, std::chrono::duration<long long int, std::ratio<1, 1> >&>::str_, fmt::v10::detail::format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > >(fmt::v10::basic_string_view<char>(((const char*)s))))'
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/core.h:2489:44:   in 'constexpr' expansion of 'fmt::v10::detail::parse_replacement_field<char, format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > >&>((p + -1), end, (* & handler))'
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/core.h:2467:38:   in 'constexpr' expansion of '(& handler)->fmt::v10::detail::format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > >::on_format_specs(adapter.fmt::v10::detail::parse_replacement_field<char, format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > >&>(const char*, const char*, format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > >&)::id_adapter::arg_id, (begin + 1), end)'
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/core.h:2639:51:   in 'constexpr' expansion of '((fmt::v10::detail::format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > >*)this)->fmt::v10::detail::format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > >::parse_funcs_[id](((fmt::v10::detail::format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > >*)this)->fmt::v10::detail::format_string_checker<char, std::chrono::duration<long long int, std::ratio<1, 1> > >::context_)'
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/core.h:2546:53:   in 'constexpr' expansion of 'fmt::v10::formatter<std::chrono::duration<long long int>, char, void>().fmt::v10::formatter<std::chrono::duration<long long int>, char, void>::parse(ctx.fmt::v10::detail::compile_parse_context<char>::<anonymous>)'
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/chrono.h:2035:38:   in 'constexpr' expansion of 'fmt::v10::detail::parse_chrono_format<char, chrono_format_checker&>(it, end, checker)'
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/chrono.h:723:29:   in 'constexpr' expansion of '((fmt::v10::detail::null_chrono_spec_handler<fmt::v10::detail::chrono_format_checker>*)(& handler))->fmt::v10::detail::null_chrono_spec_handler<fmt::v10::detail::chrono_format_checker>::on_day_of_year()'
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/chrono.h:894:52: error: 'constexpr void fmt::v10::detail::null_chrono_spec_handler<Derived>::unsupported() [with Derived = fmt::v10::detail::chrono_format_checker]' called in a constant expression
[build]   894 |   FMT_CONSTEXPR void on_day_of_year() { unsupported(); }
[build]       |                                         ~~~~~~~~~~~^~
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/chrono.h:875:22: note: 'constexpr void fmt::v10::detail::null_chrono_spec_handler<Derived>::unsupported() [with Derived = fmt::v10::detail::chrono_format_checker]' is not usable as a 'constexpr' function because:
[build]   875 |   FMT_CONSTEXPR void unsupported() {
[build]       |                      ^~~~~~~~~~~
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/chrono.h:876:45: error: call to non-'constexpr' function 'void fmt::v10::detail::chrono_format_checker::unsupported()'
[build]   876 |     static_cast<Derived*>(this)->unsupported();
[build]       |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
[build] C:/Cache/CPM/fmt/01ac001d8da09bd242594dc67d36dccb9854883e/include/fmt/chrono.h:1578:21: note: 'void fmt::v10::detail::chrono_format_checker::unsupported()' declared here
[build]  1578 |   FMT_NORETURN void unsupported() { FMT_THROW(format_error("no date")); }
[build]       |                     ^~~~~~~~~~~

I'm using fmt v10.1.1, and originally tried on fmt 9.1.0.

Please advise me if you need additionnal information !

[vitaut]

This is not implemented yet but a PR would be welcome.

[intelfx]

@vitaut I'd be willing do make this happen; any pointers where to start?

[vitaut]

@intelfx, thanks for volunteering =).

You need to add on_day_of_year just before

https://github.com/fmtlib/fmt/blob/b35d4e40fe45ada18ea3cb358a3d3fd2025033fa/include/fmt/chrono.h#L1581C29-L1581C29

and implement

https://github.com/fmtlib/fmt/blob/b35d4e40fe45ada18ea3cb358a3d3fd2025033fa/include/fmt/chrono.h#L1860C8-L1860C22

similarly to other functions in that class.