[vim] Add YouCompleteMe configuration.

tools/vim/v8.ycm_extra_conf.py

Index: tools/vim/v8.ycm_extra_conf.py
diff --git a/tools/vim/v8.ycm_extra_conf.py b/tools/vim/v8.ycm_extra_conf.py
new file mode 100644
index 0000000000000000000000000000000000000000..4de4eddd1028a1cbf400bd88d93ab4ee9fa8024c
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+++ b/tools/vim/v8.ycm_extra_conf.py
@@ -0,0 +1,197 @@
+# Copyright 2015 the V8 project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# Autocompletion config for YouCompleteMe in V8.
+#
+# USAGE:
+#
+#   1. Install YCM [https://github.com/Valloric/YouCompleteMe]
+#          (Googlers should check out [go/ycm])
+#
+#   2. Point to this config file in your .vimrc:
+#          let g:ycm_global_ycm_extra_conf =
+#              '<v8_root>/tools/vim/v8.ycm_extra_conf.py'
+#
+#   3. Profit
+#
+#
+# Usage notes:
+#
+#   * You must use ninja & clang to build V8.
+#
+#   * You must have run gyp_v8 and built V8 recently.
+#
+#
+# Hacking notes:
+#
+#   * The purpose of this script is to construct an accurate enough command line
+#     for YCM to pass to clang so it can build and extract the symbols.
+#
+#   * Right now, we only pull the -I and -D flags. That seems to be sufficient
+#     for everything I've used it for.
+#
+#   * That whole ninja & clang thing? We could support other configs if someone
+#     were willing to write the correct commands and a parser.
+#
+#   * This has only been tested on gTrusty.
+
+
+import os
+import os.path
+import subprocess
+import sys
+
+
+# Flags from YCM's default config.
+flags = [
+'-DUSE_CLANG_COMPLETER',
+'-std=c++11',
+'-x',
+'c++',
+]
+
+
+def PathExists(*args):
+  return os.path.exists(os.path.join(*args))
+
+
+def FindV8SrcFromFilename(filename):
+  """Searches for the root of the V8 checkout.
+
+  Simply checks parent directories until it finds .gclient and v8/.
+
+  Args:
+    filename: (String) Path to source file being edited.
+
+  Returns:
+    (String) Path of 'v8/', or None if unable to find.
+  """
+  curdir = os.path.normpath(os.path.dirname(filename))
+  while not (PathExists(curdir, 'v8') and PathExists(curdir, 'v8', 'DEPS')
+             and (PathExists(curdir, '.gclient')
+                  or PathExists(curdir, 'v8', '.git'))):
+    nextdir = os.path.normpath(os.path.join(curdir, '..'))
+    if nextdir == curdir:
+      return None
+    curdir = nextdir
+  return os.path.join(curdir, 'v8')
+
+
+def GetClangCommandFromNinjaForFilename(v8_root, filename):
+  """Returns the command line to build |filename|.
+
+  Asks ninja how it would build the source file. If the specified file is a
+  header, tries to find its companion source file first.
+
+  Args:
+    v8_root: (String) Path to v8/.
+    filename: (String) Path to source file being edited.
+
+  Returns:
+    (List of Strings) Command line arguments for clang.
+  """
+  if not v8_root:
+    return []
+
+  # Generally, everyone benefits from including V8's root, because all of
+  # V8's includes are relative to that.
+  v8_flags = ['-I' + os.path.join(v8_root)]
+
+  # Version of Clang used to compile V8 can be newer then version of
+  # libclang that YCM uses for completion. So it's possible that YCM's libclang
+  # doesn't know about some used warning options, which causes compilation
+  # warnings (and errors, because of '-Werror');
+  v8_flags.append('-Wno-unknown-warning-option')
+
+  # Header files can't be built. Instead, try to match a header file to its
+  # corresponding source file.
+  if filename.endswith('.h'):
+    alternates = ['.cc', '.cpp']
+    for alt_extension in alternates:
+      alt_name = filename[:-2] + alt_extension
+      if os.path.exists(alt_name):
+        filename = alt_name
+        break
+    else:
+      if filename.endswith('-inl.h'):
+        for alt_extension in alternates:
+          alt_name = filename[:-6] + alt_extension
+          if os.path.exists(alt_name):
+            filename = alt_name
+            break;
+        else:
+          # If this is a standalone -inl.h file with no source, the best we can
+          # do is try to use the default flags.
+          return v8_flags
+      else:
+        # If this is a standalone .h file with no source, the best we can do is
+        # try to use the default flags.
+        return v8_flags
+
+  sys.path.append(os.path.join(v8_root, 'tools', 'vim'))
+  from ninja_output import GetNinjaOutputDirectory
+  out_dir = os.path.realpath(GetNinjaOutputDirectory(v8_root))
+
+  # Ninja needs the path to the source file relative to the output build
+  # directory.
+  rel_filename = os.path.relpath(os.path.realpath(filename), out_dir)
+
+  # Ask ninja how it would build our source file.
+  p = subprocess.Popen(['ninja', '-v', '-C', out_dir, '-t',
+                        'commands', rel_filename + '^'],
+                       stdout=subprocess.PIPE)
+  stdout, stderr = p.communicate()
+  if p.returncode:
+    return v8_flags
+
+  # Ninja might execute several commands to build something. We want the last
+  # clang command.
+  clang_line = None
+  for line in reversed(stdout.split('\n')):
+    if 'clang' in line:
+      clang_line = line
+      break
+  else:
+    return v8_flags
+
+  # Parse flags that are important for YCM's purposes.
+  for flag in clang_line.split(' '):
+    if flag.startswith('-I'):
+      # Relative paths need to be resolved, because they're relative to the
+      # output dir, not the source.
+      if flag[2] == '/':
+        v8_flags.append(flag)
+      else:
+        abs_path = os.path.normpath(os.path.join(out_dir, flag[2:]))
+        v8_flags.append('-I' + abs_path)
+    elif flag.startswith('-std'):
+      v8_flags.append(flag)
+    elif flag.startswith('-') and flag[1] in 'DWFfmO':
+      if flag == '-Wno-deprecated-register' or flag == '-Wno-header-guard':
+        # These flags causes libclang (3.3) to crash. Remove it until things
+        # are fixed.
+        continue
+      v8_flags.append(flag)
+
+  return v8_flags
+
+
+def FlagsForFile(filename):
+  """This is the main entry point for YCM. Its interface is fixed.
+
+  Args:
+    filename: (String) Path to source file being edited.
+
+  Returns:
+    (Dictionary)
+      'flags': (List of Strings) Command line flags.
+      'do_cache': (Boolean) True if the result should be cached.
+  """
+  v8_root = FindV8SrcFromFilename(filename)
+  v8_flags = GetClangCommandFromNinjaForFilename(v8_root, filename)
+  final_flags = flags + v8_flags
+  return {
+    'flags': final_flags,
+    'do_cache': True
+  }