vim-patch:9.0.0012: signature files not detected properly (#19172)

Problem:    Signature files not detected properly.
Solution:   Add a function to better detect signature files. (Doug Kearns)
https://github.com/vim/vim/commit/cdbfc6dbab1d63aa56af316d6b13e37939e7f7a8

1 files changed, 22 insertions, 1 deletions

diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index e7f71e0f78..a3a67cacb9 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -459,7 +459,7 @@ func dist#ft#FTmm()
   setf nroff
 endfunc
 
-" Returns true if file content looks like LambdaProlog
+" Returns true if file content looks like LambdaProlog module
 func IsLProlog()
   " skip apparent comments and blank lines, what looks like 
   " LambdaProlog comment may be RAPID header
@@ -847,6 +847,27 @@ func dist#ft#FTperl()
   return 0
 endfunc
 
+" LambdaProlog and Standard ML signature files
+func dist#ft#FTsig()
+  if exists("g:filetype_sig")
+    exe "setf " .. g:filetype_sig
+    return
+  endif
+
+  let lprolog_comment = '^\s*\%(/\*\|%\)'
+  let lprolog_keyword = '^\s*sig\s\+\a'
+  let sml_comment = '^\s*(\*'
+  let sml_keyword = '^\s*\%(signature\|structure\)\s\+\a'
+
+  let line = getline(nextnonblank(1))
+
+  if line =~ lprolog_comment || line =~# lprolog_keyword
+    setf lprolog
+  elseif line =~ sml_comment || line =~# sml_keyword
+    setf sml
+  endif
+endfunc
+
 func dist#ft#FTsys()
   if exists("g:filetype_sys")
     exe "setf " .. g:filetype_sys