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, 17 insertions, 0 deletions

diff --git a/runtime/lua/vim/filetype/detect.lua b/runtime/lua/vim/filetype/detect.lua
index 342f947524..14a4381835 100644
--- a/runtime/lua/vim/filetype/detect.lua
+++ b/runtime/lua/vim/filetype/detect.lua
@@ -922,6 +922,23 @@ function M.rules(path)
   end
 end
 
+-- LambdaProlog and Standard ML signature files
+function M.sig(bufnr)
+  if vim.g.filetype_sig then
+    return vim.g.filetype_sig
+  end
+
+  local line = nextnonblank(bufnr, 1)
+
+  -- LambdaProlog comment or keyword
+  if findany(line, { '^%s*/%*', '^%s*%%', '^%s*sig%s+%a' }) then
+    return 'lprolog'
+    -- SML comment or keyword
+  elseif findany(line, { '^%s*%(%*', '^%s*signature%s+%a', '^%s*structure%s+%a' }) then
+    return 'sml'
+  end
+end
+
 -- This function checks the first 25 lines of file extension "sc" to resolve
 -- detection between scala and SuperCollider
 function M.sc(bufnr)