Improve filename completer

Add the following improvements to the filename completer:
 - allow completion of paths containing spaces;
 - allow completion of multiple paths on the same line;
 - allow completion of relative paths not starting with ".", "..", or "./";
 - allow completion of Windows environment variables (e.g. %USERPROFILE%).

ycmd/completers/cpp/flags.py

@@ -1,4 +1,4 @@
-# Copyright (C) 2011, 2012 Google Inc.
+# Copyright (C) 2011-2018 ycmd contributors
 #
 # This file is part of ycmd.
 #
@@ -27,8 +27,14 @@
 import inspect
 from future.utils import PY2, native
 from ycmd import extra_conf_store
-from ycmd.utils import ( re, ToCppStringCompatible, OnMac, OnWindows, ToUnicode,
-                         ToBytes, PathsToAllParentFolders )
+from ycmd.utils import ( ListDirectory,
+                         OnMac,
+                         OnWindows,
+                         PathsToAllParentFolders,
+                         re,
+                         ToCppStringCompatible,
+                         ToBytes,
+                         ToUnicode )
 from ycmd.responses import NoExtraConfDetected
 
 # -include-pch and --sysroot= must be listed before -include and --sysroot
@@ -515,26 +521,12 @@ def _SelectMacToolchain():
   ]
 
   for toolchain in MAC_CLANG_TOOLCHAIN_DIRS:
-    if _MacClangIncludeDirExists( toolchain ):
+    if os.path.exists( toolchain ):
       return toolchain
 
   return None
 
 
-# Ultimately, this method exists only for testability
-def _GetMacClangVersionList( candidates_dir ):
-  try:
-    return os.listdir( candidates_dir )
-  except OSError:
-    # Path might not exist, so just ignore
-    return []
-
-
-# Ultimately, this method exists only for testability
-def _MacClangIncludeDirExists( candidate_include ):
-  return os.path.exists( candidate_include )
-
-
 # Add in any clang headers found in the supplied toolchain. These are
 # required for the same reasons as described below, but unfortuantely, these
 # are in versioned directories and there is no easy way to find the "correct"
@@ -547,11 +539,11 @@ def _LatestMacClangIncludes( toolchain ):
   # It might be possible to extrace this information from xcode-select, though
   # xcode-select -p does not point at the toolchain directly
   candidates_dir = os.path.join( toolchain, 'usr', 'lib', 'clang' )
-  versions = _GetMacClangVersionList( candidates_dir )
+  versions = ListDirectory( candidates_dir )
 
   for version in reversed( sorted( versions ) ):
     candidate_include = os.path.join( candidates_dir, version, 'include' )
-    if _MacClangIncludeDirExists( candidate_include ):
+    if os.path.exists( candidate_include ):
       return [ candidate_include ]
 
   return []

ycmd/completers/cpp/include_cache.py

@@ -33,9 +33,8 @@
 from ycmd import responses
 from ycmd.completers.general.filename_completer import ( GetPathType,
                                                          GetPathTypeName )
+from ycmd.utils import GetModificationTime, ListDirectory
 
-import logging
-_logger = logging.getLogger( __name__ )
 
 """ Represents single include completion candidate.
 name is the name/string of the completion candidate,
@@ -95,7 +94,7 @@ def GetIncludes( self, path ):
 
   def _AddToCache( self, path, includes, mtime = None ):
     if not mtime:
-      mtime = _GetModificationTime( path )
+      mtime = GetModificationTime( path )
     # mtime of 0 is "a magic value" to represent inaccessible directory mtime.
     if mtime:
       with self._cache_lock:
@@ -107,7 +106,7 @@ def _GetCached( self, path ):
     with self._cache_lock:
       cache_entry = self._cache.get( path )
     if cache_entry:
-      mtime = _GetModificationTime( path )
+      mtime = GetModificationTime( path )
       if mtime > cache_entry[ 'mtime' ]:
         includes = self._ListIncludes( path )
         self._AddToCache( path, includes, mtime )
@@ -118,25 +117,10 @@ def _GetCached( self, path ):
 
 
   def _ListIncludes( self, path ):
-    try:
-      names = os.listdir( path )
-    except OSError:
-      _logger.exception( 'Can not list entries for include path %s.', path )
-      return []
-
     includes = []
-    for name in names:
+    for name in ListDirectory( path ):
       inc_path = os.path.join( path, name )
       entry_type = GetPathType( inc_path )
       includes.append( IncludeEntry( name, entry_type ) )
 
     return includes
-
-
-def _GetModificationTime( path ):
-  try:
-    return os.path.getmtime( path )
-  except OSError:
-    _logger.exception( 'Can not get modification time for include path %s.',
-                       path )
-    return 0