Fix syntax extensions being lost on syntax reload

Reapplying syntax settings with for example "syntax on" results in
loss of linux kernel extensions because they are applied only on
loading the file.

Fix this by splitting syntax configuration into a separate function,
modifying LinuxConfigure() to allow performing selective configuration,
and creating after/syntax/c.vim snippet to load syntax extensions as
part of regular syntax handling. Autocmd will only apply non-syntax
settings, such as adjusting text width and prohibiting tab expansion.

Signed-off-by: Dmitry Torokhov <[email protected]>

Author: dtor

after/syntax/c.vim

@@ -0,0 +1,3 @@
+" Extend C syntax settings with Linux Kernel-specific extensions.
+
+call g:LinuxConfigure("syntax_only")

plugin/linuxsty.vim

@@ -39,15 +39,15 @@ set wildignore+=*.ko,*.mod.c,*.order,modules.builtin
 augroup linuxsty
     autocmd!
 
-    autocmd FileType c,cpp call s:LinuxConfigure()
+    autocmd FileType c,cpp call g:LinuxConfigure("settings_only")
     autocmd FileType diff setlocal ts=8
     autocmd FileType rst setlocal ts=8 sw=8 sts=8 noet
     autocmd FileType kconfig setlocal ts=8 sw=8 sts=8 noet
     autocmd FileType dts setlocal ts=8 sw=8 sts=8 noet
     autocmd FileType make setlocal ts=8 sw=8 sts=8 noet
 augroup END
 
-function s:LinuxConfigure()
+function g:LinuxConfigure(what)
     let apply_style = 0
 
     if exists("g:linuxsty_patterns")
@@ -63,17 +63,22 @@ function s:LinuxConfigure()
     endif
 
     if apply_style
-        call s:LinuxCodingStyle()
+        call s:LinuxCodingStyle(a:what)
     endif
 endfunction
 
-command! LinuxCodingStyle call s:LinuxCodingStyle()
+command! LinuxCodingStyle call s:LinuxCodingStyle("all")
 
-function! s:LinuxCodingStyle()
-    call s:LinuxFormatting()
-    call s:LinuxKeywords()
-    call s:LinuxHighlighting()
-    call s:LinuxSavePath()
+function! s:LinuxCodingStyle(what)
+    if a:what != "settings_only"
+        call s:LinuxSyntax()
+    endif
+
+    if a:what != "syntax_only"
+        call s:LinuxFormatting()
+        call s:LinuxHighlighting()
+        call s:LinuxSavePath()
+    endif
 endfunction
 
 function s:LinuxFormatting()
@@ -87,7 +92,7 @@ function s:LinuxFormatting()
     setlocal cinoptions=:0,l1,t0,g0,(0
 endfunction
 
-function s:LinuxKeywords()
+function s:LinuxSyntax()
     syn keyword cStatement fallthrough return_ptr
     syn keyword cStorageClass noinline __always_inline __must_check
     syn keyword cStorageClass __pure __weak __noclone
@@ -98,11 +103,6 @@ function s:LinuxKeywords()
     syn keyword cType __u8 __u16 __u32 __u64 __s8 __s16 __s32 __s64
     syn keyword cType __le16 __le32 __le64 __be16 __be32 __be64
     syn keyword LinuxGuard guard scoped_guard scoped_cond_guard
-endfunction
-
-function s:LinuxHighlighting()
-    highlight default link LinuxError ErrorMsg
-    highlight default link LinuxGuard cConditional
 
     syn match LinuxError / \+\ze\t/     " spaces before tab
     syn match LinuxError /\%>100v[^()\{\}\[\]<>]\+/ " virtual column 101 and more
@@ -114,6 +114,11 @@ function s:LinuxHighlighting()
     " highlight various for_each() variants
     syn match cRepeat /\v^\s*\zs((h)?list_|device_)?for_each(_\w+)?(\()@=/
 
+    highlight default link LinuxError ErrorMsg
+    highlight default link LinuxGuard cConditional
+endfunction
+
+function s:LinuxHighlighting()
     " Highlight trailing whitespace, unless we're in insert mode and the
     " cursor's placed right after the whitespace. This prevents us from having
     " to put up with whitespace being highlighted in the middle of typing
@@ -151,7 +156,7 @@ endfunction
 
 if g:linuxsty_save_path
     if s:PathExistInCacheFile(s:path_cache_file, s:path)
-        call s:LinuxCodingStyle()
+        call s:LinuxCodingStyle("all")
     endif
 endif