Automatically use libclang if available

If the user did not request anything specific, we first try to use
libclang and only fall back to the clang executable if libclang could
not be found. Error messages are only printed in debugging mode or
if the user explicitly requested libclang.

This patch allows us to use libclang.so as soon as it can be found in
the system library path. No further configuration is required in
.vimrc.

plugin/clang_complete.vim

@@ -75,11 +75,6 @@ function! s:ClangCompleteInit()
     let g:clang_compilation_database = ''
   endif
 
-  " Only use libclang if the user clearly show intent to do so for now
-  if !exists('g:clang_use_library')
-    let g:clang_use_library = (has('python') && exists('g:clang_library_path'))
-  endif
-
   if !exists('g:clang_library_path')
     let g:clang_library_path = ''
   endif
@@ -165,11 +160,10 @@ function! s:ClangCompleteInit()
     augroup end
   endif
 
-  if g:clang_use_library == 1
-    let l:initialized = s:initClangCompletePython()
-    if l:initialized == 0
-      let g:clang_use_library = 0
-    endif
+  if !exists('g:clang_use_library') || g:clang_use_library == 1
+    " Try to use libclang. On failure, we fall back to the clang executable.
+    let l:initialized = s:initClangCompletePython(exists('g:clang_use_library'))
+    let g:clang_use_library = l:initialized
   endif
 endfunction
 
@@ -249,11 +243,13 @@ function! s:parsePathOption()
   endfor
 endfunction
 
-function! s:initClangCompletePython()
+function! s:initClangCompletePython(user_requested)
   if !has('python')
-    echoe 'clang_complete: No python support available.'
-    echoe 'Cannot use clang library, using executable'
-    echoe 'Compile vim with python support to use libclang'
+    if a:user_requested || g:clang_debug
+      echoe 'clang_complete: No python support available.'
+      echoe 'Cannot use clang library, using executable'
+      echoe 'Compile vim with python support to use libclang'
+    endif
     return 0
   endif
 
@@ -263,7 +259,7 @@ function! s:initClangCompletePython()
 
     exe 'python sys.path = ["' . s:plugin_path . '"] + sys.path'
     exe 'pyfile ' . s:plugin_path . '/libclang.py'
-    py vim.command('let l:res = ' + str(initClangComplete(vim.eval('g:clang_complete_lib_flags'), vim.eval('g:clang_compilation_database'), vim.eval('g:clang_library_path'))))
+    py vim.command('let l:res = ' + str(initClangComplete(vim.eval('g:clang_complete_lib_flags'), vim.eval('g:clang_compilation_database'), vim.eval('g:clang_library_path'), vim.eval('a:user_requested'))))
     if l:res == 0
       return 0
     endif

plugin/libclang.py

@@ -36,8 +36,13 @@ def getBuiltinHeaderPath(library_path):
     return path
   return None
 
-def initClangComplete(clang_complete_flags, clang_compilation_database, library_path):
+def initClangComplete(clang_complete_flags, clang_compilation_database, \
+                      library_path, user_requested):
   global index
+
+  debug = int(vim.eval("g:clang_debug")) == 1
+  printWarnings = (user_requested != "0") or debug
+
   if library_path != "":
     Config.set_library_path(library_path)
 
@@ -46,19 +51,20 @@ def initClangComplete(clang_complete_flags, clang_compilation_database, library_
   try:
     index = Index.create()
   except Exception, e:
-    print "Loading libclang failed, falling back to clang executable. ",
-    if library_path == "":
-      print "Consider setting g:clang_library_path"
-    else:
-      print "Are you sure '%s' contains libclang?" % library_path
+    if printWarnings:
+      print "Loading libclang failed, falling back to clang executable. ",
+      if library_path == "":
+        print "Consider setting g:clang_library_path"
+      else:
+        print "Are you sure '%s' contains libclang?" % library_path
     return 0
 
   global builtinHeaderPath
   builtinHeaderPath = None
   if not canFindBuiltinHeaders(index):
     builtinHeaderPath = getBuiltinHeaderPath(library_path)
 
-    if not builtinHeaderPath:
+    if not builtinHeaderPath and printWarnings:
       print "WARNING: libclang can not find the builtin includes."
       print "         This will cause slow code completion."
       print "         Please report the problem."