escaping -style

This fixes following error on Windows when .clang-format is not found:

error: -offset, -length and -lines can only be used for single file.

Also added undocumented feature - g:clang_format#enable_fallback_style for those who do not want any auto-formatting from clang if .clang-format is not found.

Author: hia3

autoload/clang_format.vim

@@ -50,21 +50,22 @@ function! s:stringize_options(opts) abort
 endfunction
 
 function! s:build_extra_options() abort
-    let extra_options = ''
-
     let opts = copy(g:clang_format#style_options)
     if has_key(g:clang_format#filetype_style_options, &ft)
         call extend(opts, g:clang_format#filetype_style_options[&ft])
     endif
 
-    let extra_options .= ', ' . s:stringize_options(opts)
+    let extra_options = s:stringize_options(opts)
+    if !empty(extra_options)
+        let extra_options = ', ' . extra_options
+    endif
 
     return extra_options
 endfunction
 
 function! s:make_style_options() abort
     let extra_options = s:build_extra_options()
-    return printf("'{BasedOnStyle: %s, IndentWidth: %d, UseTab: %s%s}'",
+    return printf("{BasedOnStyle: %s, IndentWidth: %d, UseTab: %s%s}",
                         \ g:clang_format#code_style,
                         \ (exists('*shiftwidth') ? shiftwidth() : &l:shiftwidth),
                         \ &l:expandtab==1 ? 'false' : 'true',
@@ -193,6 +194,8 @@ let g:clang_format#style_options = s:getg('clang_format#style_options', {})
 let g:clang_format#filetype_style_options = s:getg('clang_format#filetype_style_options', {})
 
 let g:clang_format#detect_style_file = s:getg('clang_format#detect_style_file', 1)
+let g:clang_format#enable_fallback_style = s:getg('clang_format#enable_fallback_style', 1)
+
 let g:clang_format#auto_format = s:getg('clang_format#auto_format', 0)
 let g:clang_format#auto_format_on_insert_leave = s:getg('clang_format#auto_format_on_insert_leave', 0)
 let g:clang_format#auto_formatexpr = s:getg('clang_format#auto_formatexpr', 0)
@@ -207,7 +210,11 @@ endfunction
 function! clang_format#format(line1, line2) abort
     let args = printf(' -lines=%d:%d', a:line1, a:line2)
     if ! (g:clang_format#detect_style_file && s:detect_style_file())
-        let args .= printf(' -style=%s ', s:make_style_options())
+        if g:clang_format#enable_fallback_style
+            let args .= ' ' . s:shellescape(printf('-style=%s', s:make_style_options())) . ' '
+        else
+            let args .= ' -fallback-style=none '
+        endif
     else
         let args .= ' -style=file '
     endif

t/clang_format_spec.vim

@@ -35,7 +35,7 @@ function! GetBuffer() abort
 endfunction
 
 function! ClangFormat(line1, line2, ...) abort
-    let opt = printf("-lines=%d:%d -style='{BasedOnStyle: Google, IndentWidth: %d, UseTab: %s", a:line1, a:line2, &l:shiftwidth, &l:expandtab==1 ? "false" : "true")
+    let opt = printf("-lines=%d:%d '-style={BasedOnStyle: Google, IndentWidth: %d, UseTab: %s", a:line1, a:line2, &l:shiftwidth, &l:expandtab==1 ? "false" : "true")
     let file = 'test.cpp'
 
     for a in a:000