Exclude recursive ranges from the formatter specialization for ranges #2974

Dani-Hub · 2022-07-06T17:59:19Z

No description provided.

… conditionals for filesystem::path testing that does not run into the ambiguity problem.

…cursive ranges and reject them in formatter specialization for ranges. In addition, introduce additional wrapper traits for the individual logical operands of the complete range constraints

…ter specialization for std::filesystem::path

…or the formatter specialization for std::filesystem::path

vitaut

Thanks for the PR.

vitaut · 2022-07-09T16:02:38Z

include/fmt/ranges.h

@@ -390,22 +390,36 @@ using range_formatter_type = conditional_t<
 template <typename R>
 using maybe_const_range =
    conditional_t<has_const_begin_end<R>::value, const R, R>;
+
+template <typename R>
+struct is_not_recursive_range : bool_constant<


is_not_recursive_range -> is_nonrecursive_range

Renamed as suggested.

vitaut · 2022-07-09T16:03:30Z

include/fmt/ranges.h

+template <typename R, typename Char>
+struct is_formattable_delayed : is_formattable<
+    detail::uncvref_type<detail::maybe_const_range<R>>, Char> {
+};
+
+template <typename R, typename Char>
+struct has_fallback_formatter_delayed : detail::has_fallback_formatter<
+    detail::uncvref_type<detail::maybe_const_range<R>>, Char> {
+};


What are these for? I'd suggest keeping them inlined as before.

The whole point of this P/R is to ensure that the individual parts of the condition are evaluated in short-circuit manner. In C++ without language concepts this is only possible by defining type predicates that get only evaluated if the corresponding predicate template class definition becomes instantiated. Due to std::conjunction and friends we therefore need individual class templates. The trailing delayed is intended to emphasize their job.

Could you clarify this in a comment?

I'd suggest either adding a generic thing to delay instantiation, like so:

template <template <class...> class F, typename... Args> struct delayed : F<Args...> { };

to be used as:

disjunction< delayed<is_formattable, detail::uncvref_type<detail::maybe_const_range<R>>, Char>, delayed<detail::has_fallback_formatter, detail::uncvref_type<detail::maybe_const_range<R>>, Char> >

or, if we're going to manually do our own thing, do all of it together:

template <class T, class Char> struct delayed_fallback_formattable : disjunction< is_formattable<T, Char>, detail::has_fallback_formatter<T, Char>> { };

to be used as:

conjunction< A, B, delayed_fallback_formattable<detail::uncvref_type<detail::maybe_const_range<R>>, Char> >

Put differently - instead of writing two bespoke delayed traits, write either one generic delayer or one bespoke delayed trait.

This is a good suggestion but note that has_fallback_formatter will soon go away so I suggest keeping two bespoke traits. Keeping both will simplify removing has_fallback_formatter_delayed later.

Oh. Ok that makes sense then. When you say soon, how soon?

I merged now has_fallback_formatter_delayed into is_formattable_delayed and got rid of the former.

how soon?

In the next major release about a year from now.

vitaut · 2022-07-09T16:04:15Z

include/fmt/ranges.h

+
+template <typename R>
+struct is_not_recursive_range : bool_constant<
+    !std::is_same<detail::uncvref_type<R>, R>::value> {};


Contrary to the name of this trait it only checks recursiveness but not whether R is a range. I suggest adding is_range check here.

Again, we want to prevent instantiation if the is_recursive predicate unless the is_range predicate has evaluated to true. See above. We could rename it to something different, such as is_not_recursive, if you prefer and add a comment that says that we assume here that is_range is evaluated to true.

Yes, please add a comment.

Comment added, also relating to P2286.

…ent that explains it being depending on is_range being true - Merge has_fallback_formatter_delayed into is_formattable_delayed and add comment that explains it being depending on is_not_recursive_range being true - Replace disjunction in formatter specialization by has_fallback_formatter_delayed - Get rid of unneeded detail:: prefixes within namespace detail

vitaut · 2022-07-10T13:26:29Z

Merged, thanks!

- Update from version 9.0.0 to 9.1.0 - Update of rootfile - Changelog 9.1.0 - 2022-08-27 * ``fmt::formatted_size`` now works at compile time `#3026 <https://github.com/fmtlib/fmt/pull/3026>`_ For example (`godbolt <https://godbolt.org/z/1MW5rMdf8>`__): .. code:: c++ #include <fmt/compile.h> int main() { using namespace fmt::literals; constexpr size_t n = fmt::formatted_size("{}"_cf, 42); fmt::print("{}\n", n); // prints 2 } * Fixed handling of invalid UTF-8 `#3038 <https://github.com/fmtlib/fmt/pull/3038>`_, `#3044 <https://github.com/fmtlib/fmt/pull/3044>`_, `#3056 <https://github.com/fmtlib/fmt/pull/3056>`_ * Improved Unicode support in ``ostream`` overloads of ``print`` `#2994 <https://github.com/fmtlib/fmt/pull/2994>`_, `#3001 <https://github.com/fmtlib/fmt/pull/3001>`_, `#3025 <https://github.com/fmtlib/fmt/pull/3025>`_ * Fixed handling of the sign specifier in localized formatting on systems with 32-bit ``wchar_t`` `#3041 <https://github.com/fmtlib/fmt/issues/3041>`_). * Added support for wide streams to ``fmt::streamed`` `#2994 <https://github.com/fmtlib/fmt/pull/2994>`_ * Added the ``n`` specifier that disables the output of delimiters when formatting ranges `#2981 <https://github.com/fmtlib/fmt/pull/2981>`_, `#2983 <https://github.com/fmtlib/fmt/pull/2983>`_ For example (`godbolt <https://godbolt.org/z/roKqGdj8c>`__): .. code:: c++ #include <fmt/ranges.h> #include <vector> int main() { auto v = std::vector{1, 2, 3}; fmt::print("{:n}\n", v); // prints 1, 2, 3 } * Worked around problematic ``std::string_view`` constructors introduced in C++23 `#3030 <https://github.com/fmtlib/fmt/issues/3030>`_, `#3050 <https://github.com/fmtlib/fmt/issues/3050>`_ * Improve handling (exclusion) of recursive ranges `#2968 <https://github.com/fmtlib/fmt/issues/2968>`_, `#2974 <https://github.com/fmtlib/fmt/pull/2974>`_ * Improved error reporting in format string compilation `#3055 <https://github.com/fmtlib/fmt/issues/3055>`_ * Improved the implementation of `Dragonbox <https://github.com/jk-jeon/dragonbox>`_, the algorithm used for the default floating-point formatting `#2984 <https://github.com/fmtlib/fmt/pull/2984>`_ * Fixed issues with floating-point formatting on exotic platforms. * Improved the implementation of chrono formatting `#3010 <https://github.com/fmtlib/fmt/pull/3010>`_ * Improved documentation `#2966 <https://github.com/fmtlib/fmt/pull/2966>`_, `#3009 <https://github.com/fmtlib/fmt/pull/3009>`_, `#3020 <https://github.com/fmtlib/fmt/issues/3020>`_, `#3037 <https://github.com/fmtlib/fmt/pull/3037>`_ * Improved build configuration `#2991 <https://github.com/fmtlib/fmt/pull/2991>`_, `#2995 <https://github.com/fmtlib/fmt/pull/2995>`_, `#3004 <https://github.com/fmtlib/fmt/issues/3004>`_, `#3007 <https://github.com/fmtlib/fmt/pull/3007>`_, `#3040 <https://github.com/fmtlib/fmt/pull/3040>`_ * Fixed various warnings and compilation issues `#2969 <https://github.com/fmtlib/fmt/issues/2969>`_, `#2971 <https://github.com/fmtlib/fmt/pull/2971>`_, `#2975 <https://github.com/fmtlib/fmt/issues/2975>`_, `#2982 <https://github.com/fmtlib/fmt/pull/2982>`_, `#2985 <https://github.com/fmtlib/fmt/pull/2985>`_, `#2988 <https://github.com/fmtlib/fmt/issues/2988>`_, `#3000 <https://github.com/fmtlib/fmt/issues/3000>`_, `#3006 <https://github.com/fmtlib/fmt/issues/3006>`_, `#3014 <https://github.com/fmtlib/fmt/issues/3014>`_, `#3015 <https://github.com/fmtlib/fmt/issues/3015>`_, `#3021 <https://github.com/fmtlib/fmt/pull/3021>`_, `#3023 <https://github.com/fmtlib/fmt/issues/3023>`_, `#3024 <https://github.com/fmtlib/fmt/pull/3024>`_, `#3029 <https://github.com/fmtlib/fmt/pull/3029>`_, `#3043 <https://github.com/fmtlib/fmt/pull/3043>`_, `#3052 <https://github.com/fmtlib/fmt/issues/3052>`_, `#3053 <https://github.com/fmtlib/fmt/pull/3053>`_, `#3054 <https://github.com/fmtlib/fmt/pull/3054>`_ Signed-off-by: Adolf Belka <adolf.belka@ipfire.org> Reviewed-by: Michael Tremer <michael.tremer@ipfire.org>

Dani-Hub added 8 commits July 5, 2022 17:09

2954: Add test case

d511485

Eliminate extra-test and merge it into existing std-test instead. Add…

6d14574

… conditionals for filesystem::path testing that does not run into the ambiguity problem.

fmtlib#2968: Introduce additional compile-time predicate to detect re…

26a2844

…cursive ranges and reject them in formatter specialization for ranges. In addition, introduce additional wrapper traits for the individual logical operands of the complete range constraints

fmtlib#2968: Eliminate preprocessor condition that enables the format…

c6f372b

…ter specialization for std::filesystem::path

fmtlib#2968: Eliminate preprocessor condition that enables the test f…

a1ec9fc

…or the formatter specialization for std::filesystem::path

Use own bool_constant, which is available for all C++ versions

e4c2e72

Reintroduce previous workaround but restrict to VS 2015 for now

7b05da7

Comma fix

bfff7ed

vitaut changed the title ~~Cialization for ranges needs to exclude recursive ranges~~ Exclude recursive ranges from the formatter specialization for ranges Jul 6, 2022

Dani-Hub mentioned this pull request Jul 8, 2022

Formatter specialization for ranges needs to exclude recursive ranges #2968

Closed

vitaut requested changes Jul 9, 2022

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Dani-Hub requested a review from vitaut July 10, 2022 07:26

vitaut approved these changes Jul 10, 2022

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vitaut merged commit e1d3d3a into fmtlib:master Jul 10, 2022

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Exclude recursive ranges from the formatter specialization for ranges #2974

Exclude recursive ranges from the formatter specialization for ranges #2974

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vitaut commented Jul 10, 2022

Exclude recursive ranges from the formatter specialization for ranges #2974

Exclude recursive ranges from the formatter specialization for ranges #2974

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vitaut commented Jul 10, 2022