[libc++][C++20 modules] Tests no filesystem build.

[Mordante]

Summary

Depends on D158331

libcxx/cmake/caches/Generic-no-filesystem.cmake

+set(LIBCXX_ENABLE_STD_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")

libcxx/docs/Modules.rst

  * Building BMIs
  * Running tests using the ``std`` module
  * Using the ``std`` module in external projects
  * The following "parts disabled" configuration options are supported
 
    * ``LIBCXX_ENABLE_LOCALIZATION``
    * ``LIBCXX_ENABLE_WIDE_CHARACTERS``
    * ``LIBCXX_ENABLE_THREADS``
+   * ``LIBCXX_ENABLE_FILESYSTEM``
 
 Some of the current limitations
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
  * There is no official build system support, libc++ has experimental CMake support
  * Requires CMake 3.26 for C++23 support
  * Requires CMake 3.27 for C++26 support
  * Requires Ninja 1.11

libcxx/modules/CMakeLists.txt.in

macro(compile_define_if_not condition def)
   endif()
 endmacro()
 macro(compile_define_if condition def)
   if (${condition})
     target_compile_definitions(std PRIVATE ${def})
   endif()
 endmacro()
 
-if(NOT @LIBCXX_ENABLE_FILESYSTEM@)
-  message(FATAL_ERROR "Modules without filesystem support is not yet implemented.")
-endif()
 if(NOT @LIBCXX_ENABLE_RANDOM_DEVICE@)
   message(FATAL_ERROR "Modules without randome device support is not yet implemented.")
 endif()
 if(NOT @LIBCXX_ENABLE_UNICODE@)
   message(FATAL_ERROR "Modules without Unicode support is not yet implemented.")
 endif()
 if(NOT @LIBCXX_ENABLE_EXCEPTIONS@ OR NOT @LIBCXXABI_ENABLE_EXCEPTIONS@)
   message(FATAL_ERROR "Modules without exception support is not yet implemented.")

libcxx/modules/std/filesystem.inc

export namespace std::filesystem {
 
   // [fs.path.nonmember], path non-member functions
   using std::filesystem::hash_value;
   using std::filesystem::swap;
 
   // [fs.class.filesystem.error], filesystem errors
   using std::filesystem::filesystem_error;
 
+#ifndef _LIBCPP_HAS_NO_FILESYSTEM
   // [fs.class.directory.entry], directory entries
   using std::filesystem::directory_entry;
 
   // [fs.class.directory.iterator], directory iterators
   using std::filesystem::directory_iterator;
 
   // [fs.dir.itr.nonmembers], range access for directory iterators
   using std::filesystem::begin;
   using std::filesystem::end;
 
   // [fs.class.rec.dir.itr], recursive directory iterators
   using std::filesystem::recursive_directory_iterator;
+#endif // _LIBCPP_HAS_NO_FILESYSTEM
 
   // [fs.rec.dir.itr.nonmembers], range access for recursive directory iterators
 
   // [fs.class.file.status], file status
   using std::filesystem::file_status;
   using std::filesystem::space_info;
 
   // [fs.enum], enumerations
#endif // _LIBCPP_HAS_NO_FILESYSTEM
   using std::filesystem::operator&;
   using std::filesystem::operator&=;
   using std::filesystem::operator^;
   using std::filesystem::operator^=;
   using std::filesystem::operator|;
   using std::filesystem::operator|=;
   using std::filesystem::operator~;
 
+#ifndef _LIBCPP_HAS_NO_FILESYSTEM
   // [fs.op.funcs], filesystem operations
   using std::filesystem::absolute;
   using std::filesystem::canonical;
   using std::filesystem::copy;
   using std::filesystem::copy_file;
   using std::filesystem::copy_symlink;
   using std::filesystem::create_directories;
   using std::filesystem::create_directory;
#ifndef _LIBCPP_HAS_NO_FILESYSTEM
   using std::filesystem::rename;
   using std::filesystem::resize_file;
   using std::filesystem::space;
   using std::filesystem::status;
   using std::filesystem::status_known;
   using std::filesystem::symlink_status;
   using std::filesystem::temp_directory_path;
   using std::filesystem::weakly_canonical;
+#endif // _LIBCPP_HAS_NO_FILESYSTEM
 
   // [depr.fs.path.factory]
   using std::filesystem::u8path;
-
 } // namespace std::filesystem
 
 // [fs.path.hash], hash support
 export namespace std {
   using std::hash;
 }
 
 export namespace std::ranges {
+#ifndef _LIBCPP_HAS_NO_FILESYSTEM
   using std::ranges::enable_borrowed_range;
   using std::ranges::enable_view;
+#endif // _LIBCPP_HAS_NO_FILESYSTEM
 } // namespace std::ranges

libcxx/modules/std/fstream.inc

 // -*- C++ -*-
 //===----------------------------------------------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 export namespace std {
 #ifndef _LIBCPP_HAS_NO_LOCALIZATION
   using std::basic_filebuf;
 
+#  ifndef _LIBCPP_HAS_NO_FILESYSTEM
   using std::swap;
+#  endif
 
   using std::filebuf;
 #  ifndef _LIBCPP_HAS_NO_WIDE_CHARACTERS
   using std::wfilebuf;
 #  endif
 
   using std::basic_ifstream;
 

libcxx/utils/ci/buildkite-pipeline.yml

- label: "No threads"
       timeout_in_minutes: 120
 
     - label: "No filesystem"
       command: "libcxx/utils/ci/run-buildbot generic-no-filesystem"
       artifact_paths:
         - "**/test-results.xml"
         - "**/*.abilist"
       env:
-          CC: "clang-${LLVM_HEAD_VERSION}"
-          CXX: "clang++-${LLVM_HEAD_VERSION}"
+          # Note: Modules require and absolute path for clang-scan-deps
+          # https://github.com/llvm/llvm-project/issues/61006
+          CC: "/usr/lib/llvm-${LLVM_HEAD_VERSION}/bin/clang"
+          CXX: "/usr/lib/llvm-${LLVM_HEAD_VERSION}/bin/clang++"
+          CMAKE: "/opt/bin/cmake"
           ENABLE_CLANG_TIDY: "On"
       agents:
         queue: "libcxx-builders"
         os: "linux"
       retry:
         automatic:
           - exit_status: -1  # Agent was lost
             limit: 2