Test for std::format using __cpp_lib_format

With specialization for libc++. Fixes compilation on libc++ 16-18 that
has incomplete std::format support.

Author: mochaaP

docs/spec/proxy_view.md

@@ -37,6 +37,7 @@ using proxy_view = proxy<observer_facade<F>>;
 ## Example
 
 ```cpp
+#include <cstdio>
 #include <map>
 
 #include <proxy/proxy.h>

include/proxy/v4/proxy.h

@@ -23,6 +23,9 @@
 #if __has_include(<format>)
 #include <format>
 #endif // __has_include(<format>)
+#if __cpp_lib_format || (defined(_LIBCPP_VERSION) && _LIBCPP_VERSION >= 170000)
+#define _PRO4D_HAS_FORMAT
+#endif // __cpp_lib_format || _LIBCPP_VERSION >= 170000
 #endif // __STDC_HOSTED__
 
 #if __cpp_rtti >= 199711L
@@ -2125,7 +2128,7 @@ struct weak_conversion_dispatch : cast_dispatch_base<false, true> {
 template <class F>
 using weak_conversion_overload = weak_proxy<F>() const noexcept;
 
-#if __STDC_HOSTED__ && __has_include(<format>)
+#ifdef _PRO4D_HAS_FORMAT
 template <class CharT>
 struct format_overload_traits;
 template <>
@@ -2166,7 +2169,7 @@ struct format_dispatch {
     return impl.format(self, fc);
   }
 };
-#endif // __STDC_HOSTED__ && __has_include(<format>)
+#endif // _PRO4D_HAS_FORMAT
 
 #if __cpp_rtti >= 199711L
 struct proxy_cast_context {
@@ -2273,7 +2276,7 @@ struct proxy_typeid_reflector {
 
 namespace skills {
 
-#if __STDC_HOSTED__ && __has_include(<format>)
+#ifdef _PRO4D_HAS_FORMAT
 template <class FB>
 using format =
     typename FB::template add_convention<details::format_dispatch,
@@ -2283,7 +2286,7 @@ template <class FB>
 using wformat =
     typename FB::template add_convention<details::format_dispatch,
                                          details::format_overload_t<wchar_t>>;
-#endif // __STDC_HOSTED__ && __has_include(<format>)
+#endif // _PRO4D_HAS_FORMAT
 
 #if __cpp_rtti >= 199711L
 template <class FB>
@@ -2604,7 +2607,7 @@ struct weak_dispatch : D {
 // == Adapters (std::formatter)                                               ==
 // =============================================================================
 
-#if __STDC_HOSTED__ && __has_include(<format>)
+#ifdef _PRO4D_HAS_FORMAT
 namespace std {
 
 template <pro::v4::facade F, class CharT>
@@ -2635,7 +2638,7 @@ struct formatter<pro::v4::proxy_indirect_accessor<F>, CharT> {
 };
 
 } // namespace std
-#endif // __STDC_HOSTED__ && __has_include(<format>)
+#endif // _PRO4D_HAS_FORMAT
 
 #undef PROD_UNREACHABLE
 #undef PROD_NO_UNIQUE_ADDRESS_ATTRIBUTE

include/proxy/v4/proxy.ixx

@@ -41,10 +41,10 @@ using v4::weak_proxy;
 
 namespace skills {
 
-#if __STDC_HOSTED__ && __has_include(<format>)
+#ifdef _PRO4D_HAS_FORMAT
 using skills::format;
 using skills::wformat;
-#endif // __STDC_HOSTED__ && __has_include(<format>)
+#endif // _PRO4D_HAS_FORMAT
 
 #if __cpp_rtti >= 199711L
 using skills::direct_rtti;
@@ -60,10 +60,10 @@ using skills::slim;
 
 } // namespace pro::inline v4
 
-#if __STDC_HOSTED__ && __has_include(<format>)
+#ifdef _PRO4D_HAS_FORMAT
 export namespace std {
 
 using std::formatter;
 
 } // namespace std
-#endif // __STDC_HOSTED__ && __has_include(<format>)
+#endif // _PRO4D_HAS_FORMAT

tests/proxy_dispatch_tests.cpp

@@ -829,6 +829,7 @@ TEST(ProxyDispatchTests, TestFreeAsMemDispatch) {
 }
 
 TEST(ProxyDispatchTests, TestSubstitutionDispatch) {
+#ifdef _PRO4D_HAS_FORMAT
   struct Base : pro::facade_builder              //
                 ::add_skill<pro::skills::format> //
                 ::build {};
@@ -844,4 +845,7 @@ TEST(ProxyDispatchTests, TestSubstitutionDispatch) {
   pro::proxy<Base> p3 = std::move(p1);
   ASSERT_FALSE(p1.has_value());
   ASSERT_EQ(std::format("{}", *p3), "123");
+#else
+  GTEST_SKIP() << "std::format not available";
+#endif // _PRO4D_HAS_FORMAT
 }

tests/proxy_format_tests.cpp

@@ -4,6 +4,7 @@
 #include <gtest/gtest.h>
 #include <proxy/proxy.h>
 
+#ifdef _PRO4D_HAS_FORMAT
 namespace proxy_format_tests_details {
 
 struct NonFormattable : pro::facade_builder::build {};
@@ -29,17 +30,26 @@ static_assert(
 } // namespace proxy_format_tests_details
 
 namespace details = proxy_format_tests_details;
+#endif // _PRO4D_HAS_FORMAT
 
 TEST(ProxyFormatTests, TestFormat) {
+#ifdef _PRO4D_HAS_FORMAT
   int v = 123;
   pro::proxy<details::Formattable> p = &v;
   ASSERT_EQ(std::format("{}", *p), "123");
   ASSERT_EQ(std::format("{:*<6}", *p), "123***");
+#else
+  GTEST_SKIP() << "std::format not available";
+#endif // _PRO4D_HAS_FORMAT
 }
 
 TEST(ProxyFormatTests, TestWformat) {
+#ifdef _PRO4D_HAS_FORMAT
   int v = 123;
   pro::proxy<details::Formattable> p = &v;
   ASSERT_EQ(std::format(L"{}", *p), L"123");
   ASSERT_EQ(std::format(L"{:*<6}", *p), L"123***");
+#else
+  GTEST_SKIP() << "std::format not available";
+#endif // _PRO4D_HAS_FORMAT
 }

tools/extract_example_code_from_docs.py

@@ -27,6 +27,19 @@ def extract_cpp_code(md_path: Path) -> T.Optional[str]:
 
 """.lstrip()
 
+    if "pro::skills::format" in cpp_code:
+        cpp_code = f"""
+#include <proxy/proxy.h>
+#ifdef _PRO4D_HAS_FORMAT
+{cpp_code}
+#else
+int main() {{
+  // std::format is not fully available
+  return 77;
+}}
+#endif
+""".strip()
+
     return header + cpp_code