[libc++] LWG3171: implement operator<< for filesystem::directory_entry.

Differential Revision: https://reviews.llvm.org/D116642

libcxx/docs/Status/Cxx2bIssues.csv

@@ -17,7 +17,7 @@
 "`3120 <https://wg21.link/LWG3120>`__","Unclear behavior of ``monotonic_buffer_resource::release()``","November 2020","",""
 "`3170 <https://wg21.link/LWG3170>`__","``is_always_equal`` added to ``std::allocator`` makes the standard library treat derived types as always equal","November 2020","",""
 "`3036 <https://wg21.link/LWG3036>`__","``polymorphic_allocator::destroy`` is extraneous","November 2020","",""
-"`3171 <https://wg21.link/LWG3171>`__","LWG2989 breaks ``directory_entry`` stream insertion","November 2020","",""
+"`3171 <https://wg21.link/LWG3171>`__","LWG2989 breaks ``directory_entry`` stream insertion","November 2020","|Complete|","14.0"
 "`3306 <https://wg21.link/LWG3306>`__","``ranges::advance`` violates its preconditions","November 2020","","","|ranges|"
 "`3403 <https://wg21.link/LWG3403>`__","Domain of ``ranges::ssize(E)`` doesn't ``match ranges::size(E)``","November 2020","","","|ranges|"
 "`3404 <https://wg21.link/LWG3404>`__","Finish removing subrange's conversions from pair-like","November 2020","","","|ranges|"

libcxx/include/__filesystem/directory_entry.h

@@ -23,6 +23,7 @@
 #include <chrono>
 #include <cstdint>
 #include <cstdlib>
+#include <iosfwd>
 #include <system_error>
 
 _LIBCPP_PUSH_MACROS
@@ -239,6 +240,12 @@ public:
     return __p_ >= __rhs.__p_;
   }
 
+  template <class _CharT, class _Traits>
+  _LIBCPP_INLINE_VISIBILITY
+  friend basic_ostream<_CharT, _Traits>& operator<<(basic_ostream<_CharT, _Traits>& __os, const directory_entry& __d) {
+    return __os << __d.path();
+  }
+
 private:
   friend class directory_iterator;
   friend class recursive_directory_iterator;

libcxx/test/std/experimental/iterator/ostream.joiner/ostream.joiner.ops/ostream_joiner.op.assign.pass.cpp

@@ -89,6 +89,8 @@ int main(int, char**) {
     test<char, const char *, wchar_t> ('X', chars, chars+10, L"0X1X2X3X4X5X6X7X8X9");
     test<char, const int *,  wchar_t> ('x',  ints,  ints+10, L"10x11x12x13x14x15x16x17x18x19");
 #endif
+    // TODO(var-const): uncomment when it becomes possible to instantiate a `basic_ostream` object with a sized
+    // character type (see https://llvm.org/PR53119).
 //  test<char, const char *, char16_t>('X', chars, chars+10, u"0X1X2X3X4X5X6X7X8X9");
 //  test<char, const int *,  char16_t>('x',  ints,  ints+10, u"10x11x12x13x14x15x16x17x18x19");
 //  test<char, const char *, char32_t>('X', chars, chars+10, U"0X1X2X3X4X5X6X7X8X9");

libcxx/test/std/input.output/filesystems/class.directory_entry/directory_entry.io/directory_entry.io.pass.cpp

@@ -0,0 +1,54 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03
+// UNSUPPORTED: libcpp-has-no-localization
+
+// <filesystem>
+//
+// class directory_entry
+//
+// template<class charT, class traits>
+//   friend basic_ostream<charT, traits>&
+//     operator<<(basic_ostream<charT, traits>& os, const directory_entry& d);
+
+#include "filesystem_include.h"
+#include <cassert>
+#include <sstream>
+
+#include "test_macros.h"
+#include "make_string.h"
+
+MultiStringType InStr =  MKSTR("abcdefg/\"hijklmnop\"/qrstuvwxyz/123456789");
+MultiStringType OutStr = MKSTR("\"abcdefg/\\\"hijklmnop\\\"/qrstuvwxyz/123456789\"");
+
+template <class CharT>
+void TestOutput() {
+  const char* input = static_cast<const char*>(InStr);
+  const CharT* expected_output = static_cast<const CharT*>(OutStr);
+  const fs::directory_entry dir = fs::directory_entry(fs::path(input));
+  std::basic_stringstream<CharT> stream;
+
+  auto& result = stream << dir;
+  assert(stream.str() == expected_output);
+  assert(&result == &stream);
+}
+
+int main(int, char**) {
+  TestOutput<char>();
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+  TestOutput<wchar_t>();
+#endif
+  // TODO(var-const): uncomment when it becomes possible to instantiate a `basic_ostream` object with a sized character
+  // type (see https://llvm.org/PR53119).
+  //TestOutput<char8_t>();
+  //TestOutput<char16_t>();
+  //TestOutput<char32_t>();
+
+  return 0;
+}

libcxx/test/std/input.output/filesystems/class.path/path.nonmember/path.io.pass.cpp

@@ -94,6 +94,8 @@ int main(int, char**) {
 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
   doIOTest<wchar_t>();
 #endif
+  // TODO(var-const): uncomment when it becomes possible to instantiate a `basic_ostream` object with a sized character
+  // type (see https://llvm.org/PR53119).
   //doIOTest<char16_t>();
   //doIOTest<char32_t>();
   test_LWG2989();