[Vim/YCM] Calculate system library paths based on Clang++ binary path.

The YouCompleteMe configuration still needs to determine the list of
system include paths. The current chromium.ycm_extra_conf.py logic
requires that the host machine has a 'clang' binary in its PATH that can
yield this information.

This change calculates the system include paths based on the clang++
binary used to compile the target file. It allows the use of wrappers
(E.g. goma), by looking for a clang++ command in the first and second
tokens in the compile command. It's still not perfect since the Clang
library used by ycmd might be different, but it should work better than
the current logic.

BUG=none
NOTRY=true

Review URL: https://codereview.chromium.org/1137303005

Cr-Commit-Position: refs/heads/master@{#330409}

1 files changed, 34 insertions, 13 deletions

diff --git a/tools/vim/chromium.ycm_extra_conf.py b/tools/vim/chromium.ycm_extra_conf.py
index 76fce67..6f74d58 100644
--- a/tools/vim/chromium.ycm_extra_conf.py
+++ b/tools/vim/chromium.ycm_extra_conf.py
@@ -40,21 +40,28 @@
 import os
 import os.path
 import re
+import shlex
 import subprocess
 import sys
 
 
-def SystemIncludeDirectoryFlags():
+def SystemIncludeDirectoryFlags(clang_binary, clang_flags):
   """Determines compile flags to include the system include directories.
 
   Use as a workaround for https://github.com/Valloric/YouCompleteMe/issues/303
 
+  Args:
+    clang_binary: (String) Path to clang binary.
+    clang_flags: (List of Strings) List of additional flags to clang. It may
+      affect the choice of system include directories if -stdlib= is specified.
+
   Returns:
     (List of Strings) Compile flags to append.
   """
+  all_flags = ['-v', '-E', '-x', 'c++'] + clang_flags + ['-']
   try:
     with open(os.devnull, 'rb') as DEVNULL:
-      output = subprocess.check_output(['clang', '-v', '-E', '-x', 'c++', '-'],
+      output = subprocess.check_output([clang_binary] + all_flags,
                                        stdin=DEVNULL, stderr=subprocess.STDOUT)
   except:
     return []
@@ -69,21 +76,19 @@ def SystemIncludeDirectoryFlags():
       flags.append(path)
   return flags
 
-
-_system_include_flags = SystemIncludeDirectoryFlags()
-
 # Flags from YCM's default config.
-flags = [
-'-DUSE_CLANG_COMPLETER',
-'-std=c++11',
-'-x',
-'c++',
+_default_flags = [
+  '-DUSE_CLANG_COMPLETER',
+  '-std=c++11',
+  '-x',
+  'c++',
 ]
 
-
 def PathExists(*args):
   return os.path.exists(os.path.join(*args))
 
+def LooksLikeClangCommand(command):
+  return command.endswith('clang++') or command.endswith('clang')
 
 def FindChromeSrcFromFilename(filename):
   """Searches for the root of the Chromium checkout.
@@ -190,7 +195,8 @@ def GetClangCommandFromNinjaForFilename(chrome_root, filename):
     return chrome_flags
 
   # Parse flags that are important for YCM's purposes.
-  for flag in clang_line.split(' '):
+  clang_tokens = shlex.split(clang_line)
+  for flag in clang_tokens:
     if flag.startswith('-I'):
       # Relative paths need to be resolved, because they're relative to the
       # output dir, not the source.
@@ -208,6 +214,21 @@ def GetClangCommandFromNinjaForFilename(chrome_root, filename):
         continue
       chrome_flags.append(flag)
 
+  # Assume that the command for invoking clang++ looks like one of the
+  # following:
+  #   1) /path/to/clang/clang++ arguments
+  #   2) /some/wrapper /path/to/clang++ arguments
+  #
+  # We'll look for a token that looks like Clang command within the first two
+  # tokens of the command line and treat it as the clang++ binary. Using the
+  # command line upto the Clang-like token isn't always feasible since the
+  # wrapper may not like the invocation used by SystemIncludeDirectoryFlags()
+  # although the real clang++ binary does.
+  for command in clang_tokens[0:2]:
+    if LooksLikeClangCommand(command):
+      chrome_flags += SystemIncludeDirectoryFlags(command, chrome_flags)
+      break
+
   return chrome_flags
 
 
@@ -225,7 +246,7 @@ def FlagsForFile(filename):
   chrome_root = FindChromeSrcFromFilename(filename)
   chrome_flags = GetClangCommandFromNinjaForFilename(chrome_root,
                                                      filename)
-  final_flags = flags + chrome_flags + _system_include_flags
+  final_flags = _default_flags + chrome_flags
 
   return {
     'flags': final_flags,