Fallback to boost_filesystem if no filesystem lib is present

cpp/ycm/CMakeLists.txt

@@ -277,12 +277,19 @@ if ( UNIX AND NOT ( APPLE OR SYSTEM_IS_OPENBSD OR HAIKU ) )
 endif()
 
 # Check if we need to add -lstdc++fs or -lc++fs or nothing
-file( WRITE ${CMAKE_CURRENT_BINARY_DIR}/main.cpp "#include <filesystem>\nint main( int argc, char ** argv ) {\n  std::filesystem::path p( argv[ 0 ] );\n  return p.string().length();\n}" )
+file( WRITE ${CMAKE_CURRENT_BINARY_DIR}/main.cpp "#if defined(USE_BOOST_FS)\n#include <boost/filesystem.hpp>\nnamespace fs = boost::filesystem;\n#else\n#include <filesystem>\nnamespace fs = std::filesystem;\n#endif\nint main( int argc, char ** argv ) {\n  fs::path p( argv[ 0 ] );\n  return p.parent_path().string().length();\n}" )
 try_compile( STD_FS_NO_LIB_NEEDED ${CMAKE_CURRENT_BINARY_DIR}
              SOURCES ${CMAKE_CURRENT_BINARY_DIR}/main.cpp
              CXX_STANDARD 17
              CXX_STANDARD_REQUIRED TRUE
              CXX_EXTENSIONS ${NEEDS_EXTENSIONS} )
+try_compile( STD_FS_NEEDS_BOOSTFS ${CMAKE_CURRENT_BINARY_DIR}
+             SOURCES ${CMAKE_CURRENT_BINARY_DIR}/main.cpp
+             CXX_STANDARD 17
+             CXX_STANDARD_REQUIRED TRUE
+             CXX_EXTENSIONS ${NEEDS_EXTENSIONS}
+             COMPILE_DEFINITIONS -DUSE_BOOST_FS
+             LINK_LIBRARIES boost_system boost_filesystem)
 try_compile( STD_FS_NEEDS_STDCXXFS ${CMAKE_CURRENT_BINARY_DIR}
              SOURCES ${CMAKE_CURRENT_BINARY_DIR}/main.cpp
              CXX_STANDARD 17
@@ -299,12 +306,19 @@ file( REMOVE ${CMAKE_CURRENT_BINARY_DIR}/main.cpp )
 
 if( ${STD_FS_NEEDS_STDCXXFS} )
   set( STD_FS_LIB stdc++fs )
+  set( STD_FS_DEFINES "" )
 elseif( ${STD_FS_NEEDS_CXXFS} )
   set( STD_FS_LIB c++fs )
+  set( STD_FS_DEFINES "" )
 elseif( ${STD_FS_NO_LIB_NEEDED} )
   set( STD_FS_LIB "" )
+  set( STD_FS_DEFINES "" )
+elseif( ${STD_FS_NEEDS_BOOSTFS} )
+  message( STATUS "Using boost_filesystem" )
+  set( STD_FS_LIB boost_system boost_filesystem )
+  set( STD_FS_DEFINES -DUSE_BOOST_FS )
 else()
-  message( FATAL_ERROR "Unknown compiler - C++17 filesystem library missing" )
+  message( FATAL_ERROR "Unknown compiler - C++17 filesystem library and boost_filesystem both missing" )
 endif()
 
 # Check if Abseil supports this environment
@@ -347,6 +361,9 @@ if ( USE_CLANG_COMPLETER AND NOT LIBCLANG_TARGET )
                           "your configuration" )
 endif()
 
+target_compile_definitions( ${PROJECT_NAME}
+                            PUBLIC ${STD_FS_DEFINES}
+                          )
 target_link_libraries( ${PROJECT_NAME}
                        PUBLIC ${Python3_LIBRARIES}
                        PUBLIC ${LIBCLANG_TARGET}

cpp/ycm/ClangCompleter/TranslationUnit.cpp

@@ -23,7 +23,6 @@
 
 #include <algorithm>
 #include <cstdlib>
-#include <filesystem>
 #include <memory>
 
 using std::unique_lock;

cpp/ycm/IdentifierUtils.cpp

@@ -19,15 +19,12 @@
 #include "Utils.h"
 
 #include <array>
-#include <filesystem>
 #include <functional>
 #include <string_view>
 #include <utility>
 
 namespace YouCompleteMe {
 
-namespace fs = std::filesystem;
-
 namespace {
 
 // List of languages Universal Ctags supports:

cpp/ycm/IdentifierUtils.h

@@ -20,12 +20,12 @@
 
 #include "IdentifierDatabase.h"
 
-#include <filesystem>
+#include "Utils.h"
 
 namespace YouCompleteMe {
 
 YCM_EXPORT FiletypeIdentifierMap ExtractIdentifiersFromTagsFile(
-  const std::filesystem::path &path_to_tag_file );
+  const fs::path &path_to_tag_file );
 
 } // namespace YouCompleteMe
 

cpp/ycm/Utils.cpp

@@ -18,14 +18,11 @@
 #include "Utils.h"
 
 #include <cmath>
-#include <filesystem>
 #include <fstream>
 #include <limits>
 #include <string>
 #include <vector>
 
-namespace fs = std::filesystem;
-
 namespace YouCompleteMe {
 
 std::vector< std::string > ReadUtf8File( const fs::path &filepath ) {

cpp/ycm/Utils.h

@@ -20,14 +20,19 @@
 
 #include <algorithm>
 #include <cmath>
-#include <filesystem>
 #include <limits>
 #include <string>
 #include <string_view>
 #include <type_traits>
 #include <vector>
 
+#if defined(USE_BOOST_FS)
+#include <boost/filesystem.hpp>
+namespace fs = boost::filesystem;
+#else
+#include <filesystem>
 namespace fs = std::filesystem;
+#endif
 
 namespace YouCompleteMe {
 

cpp/ycm/tests/IdentifierUtils_test.cpp

@@ -21,11 +21,9 @@
 
 #include <gtest/gtest.h>
 #include <gmock/gmock.h>
-#include <filesystem>
 
 namespace YouCompleteMe {
 
-namespace fs = std::filesystem;
 using ::testing::ElementsAre;
 using ::testing::ContainerEq;
 using ::testing::IsEmpty;

cpp/ycm/tests/TestUtils.cpp

@@ -19,18 +19,6 @@
 
 #include <whereami.c>
 
-namespace std {
-
-namespace filesystem {
-
-void PrintTo( const fs::path &path, std::ostream *os ) {
-  *os << path;
-}
-
-} // namespace filesystem
-
-} // namespace std
-
 namespace YouCompleteMe {
 
 std::ostream& operator<<( std::ostream& os, const CodePointTuple &code_point ) {

cpp/ycm/tests/TestUtils.h

@@ -20,17 +20,15 @@
 
 #include "Character.h"
 #include "CodePoint.h"
+#include "Utils.h"
 #include "Word.h"
 
-#include <filesystem>
 #include <gmock/gmock.h>
 #include <string>
 #include <vector>
 
 using ::testing::PrintToString;
 
-namespace fs = std::filesystem;
-
 namespace YouCompleteMe {
 
 // Tuple-like structures to help writing tests for CodePoint, Character, and