4 files changed, 567 insertions, 110 deletions

diff --git a/runtime/lua/vim/_editor.lua b/runtime/lua/vim/_editor.lua
index dc25d68f61..e6ab48f30d 100644
--- a/runtime/lua/vim/_editor.lua
+++ b/runtime/lua/vim/_editor.lua
@@ -406,7 +406,6 @@ function vim.defer_fn(fn, timeout)
     timeout,
     0,
     vim.schedule_wrap(function()
-      timer:stop()
       timer:close()
 
       fn()
diff --git a/runtime/lua/vim/filetype.lua b/runtime/lua/vim/filetype.lua
index fed0231ae9..8321e0b11e 100644
--- a/runtime/lua/vim/filetype.lua
+++ b/runtime/lua/vim/filetype.lua
@@ -810,11 +810,11 @@ local extension = {
   R = function(path, bufnr)
     require('vim.filetype.detect').r(bufnr)
   end,
-  asm = function()
-    vim.fn['dist#ft#FTasm']()
+  asm = function(path, bufnr)
+    require('vim.filetype.detect').asm(bufnr)
   end,
-  bas = function()
-    vim.fn['dist#ft#FTbas']()
+  bas = function(path, bufnr)
+    require('vim.filetype.detect').bas(bufnr)
   end,
   bi = function()
     vim.fn['dist#ft#FTbas']()
@@ -828,11 +828,11 @@ local extension = {
   btm = function(path, bufnr)
     return require('vim.filetype.detect').btm(bufnr)
   end,
-  c = function()
-    vim.fn['dist#ft#FTlpc']()
+  c = function(path, bufnr)
+    return require('vim.filetype.detect').lpc(bufnr)
   end,
-  ch = function()
-    vim.fn['dist#ft#FTchange']()
+  ch = function(path, bufnr)
+    return require('vim.filetype.detect').change(bufnr)
   end,
   com = function()
     vim.fn['dist#ft#BindzoneCheck']('dcl')
@@ -843,8 +843,8 @@ local extension = {
   csh = function()
     vim.fn['dist#ft#CSH']()
   end,
-  d = function()
-    vim.fn['dist#ft#DtraceCheck']()
+  d = function(path, bufnr)
+    return require('vim.filetype.detect').dtrace(bufnr)
   end,
   db = function()
     vim.fn['dist#ft#BindzoneCheck']('')
@@ -862,30 +862,30 @@ local extension = {
     vim.fn['dist#ft#SetFileTypeSH']('bash')
   end,
   ent = function(path, bufnr)
-    return require('vim.filetype.detect').ent(bufnr)
+    require('vim.filetype.detect').ent(bufnr)
   end,
   env = function()
     vim.fn['dist#ft#SetFileTypeSH'](vim.fn.getline(1))
   end,
   eu = function(path, bufnr)
-    return require('vim.filetype.detect').euphoria(bufnr)
+    require('vim.filetype.detect').euphoria(bufnr)
   end,
   ew = function(path, bufnr)
-    return require('vim.filetype.detect').euphoria(bufnr)
+    require('vim.filetype.detect').euphoria(bufnr)
   end,
   ex = function(path, bufnr)
-    return require('vim.filetype.detect').ex(bufnr)
+    require('vim.filetype.detect').ex(bufnr)
   end,
   exu = function(path, bufnr)
-    return require('vim.filetype.detect').euphoria(bufnr)
+    require('vim.filetype.detect').euphoria(bufnr)
   end,
   exw = function(path, bufnr)
-    return require('vim.filetype.detect').euphoria(bufnr)
+    require('vim.filetype.detect').euphoria(bufnr)
   end,
   frm = function(path, bufnr)
     require('vim.filetype.detect').frm(bufnr)
   end,
-  fs = function()
+  fs = function(path, bufnr)
     vim.fn['dist#ft#FTfs']()
   end,
   h = function(path, bufnr)
@@ -897,8 +897,8 @@ local extension = {
   html = function()
     vim.fn['dist#ft#FThtml']()
   end,
-  i = function()
-    vim.fn['dist#ft#FTprogress_asm']()
+  i = function(path, bufnr)
+    require('vim.filetype.detect').progress_asm(bufnr)
   end,
   idl = function(path, bufnr)
     require('vim.filetype.detect').idl(bufnr)
@@ -912,26 +912,26 @@ local extension = {
   ksh = function()
     vim.fn['dist#ft#SetFileTypeSH']('ksh')
   end,
-  lst = function()
-    vim.fn['dist#ft#FTasm']()
+  lst = function(path, bufnr)
+    require('vim.filetype.detect').asm(bufnr)
   end,
-  m = function()
-    vim.fn['dist#ft#FTm']()
+  m = function(path, bufnr)
+    require('vim.filetype.detect').m(bufnr)
   end,
-  mac = function()
-    vim.fn['dist#ft#FTasm']()
+  mac = function(path, bufnr)
+    require('vim.filetype.detect').asm(bufnr)
   end,
   mc = function(path, bufnr)
     require('vim.filetype.detect').mc(bufnr)
   end,
-  mm = function()
-    vim.fn['dist#ft#FTmm']()
+  mm = function(path, bufnr)
+    require('vim.filetype.detect').mm(bufnr)
   end,
   mms = function(path, bufnr)
     require('vim.filetype.detect').mms(bufnr)
   end,
-  p = function()
-    vim.fn['dist#ft#FTprogress_pascal']()
+  p = function(path, bufnr)
+    require('vim.filetype.detect').progress_pascal(bufnr)
   end,
   patch = function(path, bufnr)
     local firstline = getline(bufnr, 1)
@@ -959,8 +959,8 @@ local extension = {
   rdf = function(path, bufnr)
     require('vim.filetype.detect').redif(bufnr)
   end,
-  rules = function()
-    vim.fn['dist#ft#FTRules']()
+  rules = function(path, bufnr)
+    require('vim.filetype.detect').rules(path, bufnr)
   end,
   sc = function(path, bufnr)
     require('vim.filetype.detect').sc(bufnr)
@@ -1559,13 +1559,13 @@ local pattern = {
   ['%.zlog.*'] = starsetf('zsh'),
   ['%.zsh.*'] = starsetf('zsh'),
   ['.*%.[1-9]'] = function(path, bufnr)
-    return require('vim.filetype.detect').nroff(bufnr)
+    require('vim.filetype.detect').nroff(bufnr)
   end,
-  ['.*%.[aA]'] = function()
-    vim.fn['dist#ft#FTasm']()
+  ['.*%.[aA]'] = function(path, bufnr)
+    require('vim.filetype.detect').asm(bufnr)
   end,
-  ['.*%.[sS]'] = function()
-    vim.fn['dist#ft#FTasm']()
+  ['.*%.[sS]'] = function(path, bufnr)
+    require('vim.filetype.detect').asm(bufnr)
   end,
   ['.*%.properties_.._.._.*'] = starsetf('jproperties'),
   ['.*%.vhdl_[0-9].*'] = starsetf('vhdl'),
@@ -1575,8 +1575,8 @@ local pattern = {
   ['.*/Xresources/.*'] = starsetf('xdefaults'),
   ['.*/app%-defaults/.*'] = starsetf('xdefaults'),
   ['.*/bind/db%..*'] = starsetf('bindzone'),
-  ['.*/debian/patches/.*'] = function()
-    vim.fn['dist#ft#Dep3patch']()
+  ['.*/debian/patches/.*'] = function(path, bufnr)
+    require('vim.filetype.detect').dep3patch(path, bufnr)
   end,
   ['.*/etc/Muttrc%.d/.*'] = starsetf('muttrc'),
   ['.*/etc/apache2/.*%.conf.*'] = starsetf('apache'),
@@ -1680,24 +1680,24 @@ local pattern = {
       return 'git'
     end
   end,
-  ['.*%.[Cc][Ff][Gg]'] = function()
-    vim.fn['dist#ft#FTcfg']()
+  ['.*%.[Cc][Ff][Gg]'] = function(path, bufnr)
+    require('vim.filetype.detect').cfg(bufnr)
   end,
-  ['.*%.[Dd][Aa][Tt]'] = function()
-    vim.fn['dist#ft#FTdat']()
+  ['.*%.[Dd][Aa][Tt]'] = function(path, bufnr)
+    require('vim.filetype.detect').dat(bufnr)
   end,
-  ['.*%.[Mm][Oo][Dd]'] = function()
-    vim.fn['dist#ft#FTmod']()
+  ['.*%.[Mm][Oo][Dd]'] = function(path, bufnr)
+    require('vim.filetype.detect').mod(path, bufnr)
   end,
-  ['.*%.[Ss][Rr][Cc]'] = function()
-    vim.fn['dist#ft#FTsrc']()
+  ['.*%.[Ss][Rr][Cc]'] = function(path, bufnr)
+    require('vim.filetype.detect').src(bufnr)
   end,
   ['.*%.[Ss][Uu][Bb]'] = 'krl',
-  ['.*%.[Pp][Rr][Gg]'] = function()
-    vim.fn['dist#ft#FTprg']()
+  ['.*%.[Pp][Rr][Gg]'] = function(path, bufnr)
+    require('vim.filetype.detect').prg(bufnr)
   end,
-  ['.*%.[Ss][Yy][Ss]'] = function()
-    vim.fn['dist#ft#FTsys']()
+  ['.*%.[Ss][Yy][Ss]'] = function(path, bufnr)
+    require('vim.filetype.detect').sys(bufnr)
   end,
   -- Neovim only
   ['.*/queries/.*%.scm'] = 'query', -- tree-sitter queries
diff --git a/runtime/lua/vim/filetype/detect.lua b/runtime/lua/vim/filetype/detect.lua
index 4c363e7403..da59625353 100644
--- a/runtime/lua/vim/filetype/detect.lua
+++ b/runtime/lua/vim/filetype/detect.lua
@@ -1,15 +1,28 @@
+-- Contains filetype detection functions converted to Lua from Vim's autoload/runtime/dist/ft.vim file.
+
+-- Here are a few guidelines to follow when porting a new function:
+--  * Sort the function alphabetically and omit 'ft' or 'check' from the new function name.
+--  * Use ':find' instead of ':match' / ':sub' if possible.
+--  * When '=~' is used to match a pattern, there are two possibilities:
+--     - If the pattern only contains lowercase characters, treat the comparison as case-insensitive.
+--     - Otherwise, treat it as case-sensitive.
+--     (Basically, we apply 'smartcase': if upper case characters are used in the original pattern, then
+--     it's likely that case does matter).
+--  * When '\k', '\<' or '\>' is used in a pattern, use the 'matchregex' function.
+--     Note that vim.regex is case-sensitive by default, so add the '\c' flag if only lowercase letters
+--     are present in the pattern:
+--     Example:
+--     `if line =~ '^\s*unwind_protect\>'` => `if matchregex(line, [[\c^\s*unwind_protect\>]])`
+
 local M = {}
 
 ---@private
-local function getlines(bufnr, start_lnum, end_lnum, opts)
+local function getlines(bufnr, start_lnum, end_lnum)
   if not end_lnum then
     -- Return a single line as a string
     return vim.api.nvim_buf_get_lines(bufnr, start_lnum - 1, start_lnum, false)[1]
   end
-
-  local lines = vim.api.nvim_buf_get_lines(bufnr, start_lnum - 1, end_lnum, false)
-  opts = opts or {}
-  return opts.concat and (table.concat(lines) or '') or lines
+  return vim.api.nvim_buf_get_lines(bufnr, start_lnum - 1, end_lnum, false)
 end
 
 ---@private
@@ -22,16 +35,103 @@ local function findany(s, patterns)
   return false
 end
 
+---@private
+local function nextnonblank(bufnr, start_lnum)
+  for _, line in ipairs(getlines(bufnr, start_lnum, -1)) do
+    if not line:find('^%s*$') then
+      return line
+    end
+  end
+  return nil
+end
+
+---@private
+local matchregex = (function()
+  local cache = {}
+  return function(line, pattern)
+    if line == nil then
+      return nil
+    end
+    if not cache[pattern] then
+      cache[pattern] = vim.regex(pattern)
+    end
+    return cache[pattern]:match_str(line)
+  end
+end)()
+
 -- luacheck: push no unused args
 -- luacheck: push ignore 122
 
-function M.asm(path, bufnr) end
+-- This function checks for the kind of assembly that is wanted by the user, or
+-- can be detected from the first five lines of the file.
+function M.asm(bufnr)
+  -- Make sure b:asmsyntax exists
+  if not vim.b[bufnr].asmsyntax then
+    vim.b[bufnr].asmsyntax = ''
+  end
 
-function M.asm_syntax(path, bufnr) end
+  if vim.b[bufnr].asmsyntax == '' then
+    M.asm_syntax(bufnr)
+  end
 
-function M.bas(path, bufnr) end
+  -- If b:asmsyntax still isn't set, default to asmsyntax or GNU
+  if vim.b[bufnr].asmsyntax == '' then
+    if vim.g.asmsyntax and vim.g.asmsyntax ~= 0 then
+      vim.b[bufnr].asmsyntax = vim.g.asmsyntax
+    else
+      vim.b[bufnr].asmsyntax = 'asm'
+    end
+  end
+  vim.bo[bufnr].filetype = vim.fn.fnameescape(vim.b[bufnr].asmsyntax)
+end
+
+-- Checks the first 5 lines for a asmsyntax=foo override.
+-- Only whitespace characters can be present immediately before or after this statement.
+function M.asm_syntax(bufnr)
+  local lines = table.concat(getlines(bufnr, 1, 5), ' '):lower()
+  local match = lines:match('%sasmsyntax=([a-zA-Z0-9]+)%s')
+  if match then
+    vim.b['asmsyntax'] = match
+  elseif findany(lines, { '%.title', '%.ident', '%.macro', '%.subtitle', '%.library' }) then
+    vim.b['asmsyntax'] = 'vmasm'
+  end
+end
 
-function M.bindzone(path, bufnr) end
+local visual_basic_content = { 'vb_name', 'begin vb%.form', 'begin vb%.mdiform', 'begin vb%.usercontrol' }
+
+-- See frm() for Visual Basic form file detection
+function M.bas(bufnr)
+  if vim.g.filetype_bas then
+    vim.bo[bufnr].filetype = vim.g.filetype_bas
+    return
+  end
+
+  -- Most frequent FreeBASIC-specific keywords in distro files
+  local fb_keywords =
+    [[\c^\s*\%(extern\|var\|enum\|private\|scope\|union\|byref\|operator\|constructor\|delete\|namespace\|public\|property\|with\|destructor\|using\)\>\%(\s*[:=(]\)\@!]]
+  local fb_preproc =
+    [[\c^\s*\%(#\a\+\|option\s\+\%(byval\|dynamic\|escape\|\%(no\)\=gosub\|nokeyword\|private\|static\)\>\)]]
+
+  local fb_comment = "^%s*/'"
+  -- OPTION EXPLICIT, without the leading underscore, is common to many dialects
+  local qb64_preproc = [[\c^\s*\%($\a\+\|option\s\+\%(_explicit\|_\=explicitarray\)\>\)]]
+
+  for _, line in ipairs(getlines(bufnr, 1, 100)) do
+    if line:find(fb_comment) or matchregex(line, fb_preproc) or matchregex(line, fb_keywords) then
+      vim.bo[bufnr].filetype = 'freebasic'
+      return
+    elseif matchregex(line, qb64_preproc) then
+      vim.bo[bufnr].filetype = 'qb64'
+      return
+    elseif findany(line:lower(), visual_basic_content) then
+      vim.bo[bufnr].filetype = 'vb'
+      return
+    end
+  end
+  vim.bo[bufnr].filetype = 'basic'
+end
+
+function M.bindzone(bufnr, default_ft) end
 
 function M.btm(bufnr)
   if vim.g.dosbatch_syntax_for_btm and vim.g.dosbatch_syntax_for_btm ~= 0 then
@@ -47,14 +147,11 @@ local function is_rapid(bufnr, extension)
     local line = getlines(bufnr, 1):lower()
     return findany(line, { 'eio:cfg', 'mmc:cfg', 'moc:cfg', 'proc:cfg', 'sio:cfg', 'sys:cfg' })
   end
-  local first = '^%s*module%s+%S+%s*'
-  -- Called from mod, prg or sys functions
-  for _, line in ipairs(getlines(bufnr, 1, -1)) do
-    if not line:find('^%s*$') then
-      return findany(line:lower(), { '^%s*%%%%%%', first .. '(', first .. '$' })
-    end
+  local line = nextnonblank(bufnr, 1)
+  if line then
+    -- Called from mod, prg or sys functions
+    return matchregex(line:lower(), [[\c\v^\s*%(\%{3}|module\s+\k+\s*%(\(|$))]])
   end
-  -- Only found blank lines
   return false
 end
 
@@ -68,17 +165,110 @@ function M.cfg(bufnr)
   end
 end
 
-function M.change(path, bufnr) end
+-- This function checks if one of the first ten lines start with a '@'.  In
+-- that case it is probably a change file.
+-- If the first line starts with # or ! it's probably a ch file.
+-- If a line has "main", "include", "//" or "/*" it's probably ch.
+-- Otherwise CHILL is assumed.
+function M.change(bufnr)
+  local first_line = getlines(bufnr, 1)
+  if findany(first_line, { '^#', '^!' }) then
+    vim.bo[bufnr].filetype = 'ch'
+    return
+  end
+  for _, line in ipairs(getlines(bufnr, 1, 10)) do
+    if line:find('^@') then
+      vim.bo[bufnr].filetype = 'change'
+      return
+    end
+    if line:find('MODULE') then
+      vim.bo[bufnr].filetype = 'chill'
+      return
+    elseif findany(line:lower(), { 'main%s*%(', '#%s*include', '//' }) then
+      vim.bo[bufnr].filetype = 'ch'
+      return
+    end
+  end
+  vim.bo[bufnr].filetype = 'chill'
+end
 
 function M.csh(path, bufnr) end
 
-function M.dat(path, bufnr) end
+-- Determine if a *.dat file is Kuka Robot Language
+-- TODO: this one fails for some reason, so I omitted it. #18219 should be merged first.
+function M.dat(bufnr)
+  -- if vim.g.filetype_dat then
+  --   vim.bo[bufnr].filetype = vim.g.filetype_dat
+  --   return
+  -- end
+  -- local line = nextnonblank(bufnr, 1):lower()
+  -- if findany(line, { "^%s*&%w+", "^%s*defdat" }) then
+  --   vim.bo[bufnr].filetype = "krl"
+  -- end
+end
 
-function M.dep3patch(path, bufnr) end
+-- This function is called for all files under */debian/patches/*, make sure not
+-- to non-dep3patch files, such as README and other text files.
+function M.dep3patch(path, bufnr)
+  local file_name = vim.fn.fnamemodify(path, ':t')
+  if file_name == 'series' then
+    return
+  end
 
-function M.dtrace(path, bufnr) end
+  for _, line in ipairs(getlines(bufnr, 1, 100)) do
+    if
+      findany(line, {
+        '^Description:',
+        '^Subject:',
+        '^Origin:',
+        '^Bug:',
+        '^Forwarded:',
+        '^Author:',
+        '^From:',
+        '^Reviewed%-by:',
+        '^Acked%-by:',
+        '^Last%-Updated:',
+        '^Applied%-Upstream:',
+      })
+    then
+      vim.bo[bufnr].filetype = 'dep3patch'
+      return
+    elseif line:find('^%-%-%-') then
+      -- End of headers found. stop processing
+      return
+    end
+  end
+end
 
-function M.e(path, bufnr) end
+function M.dtrace(bufnr)
+  local did_filetype = vim.fn.did_filetype()
+  if did_filetype and did_filetype ~= 0 then
+    -- Filetype was already detected
+    return
+  end
+  for _, line in ipairs(getlines(bufnr, 1, 100)) do
+    if matchregex(line, [[\c^module\>\|^import\>]]) then
+      --  D files often start with a module and/or import statement.
+      vim.bo[bufnr].filetype = 'd'
+      return
+    elseif findany(line, { '^#!%S+dtrace', '#pragma%s+D%s+option', ':%S-:%S-:' }) then
+      vim.bo[bufnr].filetype = 'dtrace'
+      return
+    end
+  end
+  vim.bo[bufnr].filetype = 'd'
+end
+
+function M.e(path, bufnr)
+  if vim.g.filetype_euphoria then
+    vim.bo[bufnr].filetype = vim.g.filetype_euphoria
+    return
+  end
+  -- TODO: WIP
+  -- for _, line in ipairs(getlines(bufnr, 1, 100)) do
+  --   if line:find("^$")
+  -- end
+end
 
 -- This function checks for valid cl syntax in the first five lines.
 -- Look for either an opening comment, '#', or a block start, '{'.
@@ -110,8 +300,7 @@ function M.ex(bufnr)
     vim.bo[bufnr].filetype = vim.g.filetype_euphoria
   else
     for _, line in ipairs(getlines(bufnr, 1, 100)) do
-      -- TODO: in the Vim regex, \> is used to match the end of the word, can this be omitted?
-      if findany(line, { '^%-%-', '^ifdef', '^include' }) then
+      if matchregex(line, [[\c^--\|^ifdef\>\|^include\>]]) then
         vim.bo[bufnr].filetype = 'euphoria3'
         return
       end
@@ -138,22 +327,34 @@ end
 function M.frm(bufnr)
   if vim.g.filetype_frm then
     vim.bo[bufnr].filetype = vim.g.filetype_frm
+    return
+  end
+  local lines = table.concat(getlines(bufnr, 1, 5)):lower()
+  if findany(lines, visual_basic_content) then
+    vim.bo[bufnr].filetype = 'vb'
   else
-    -- Always ignore case
-    local lines = getlines(bufnr, 1, 5, { concat = true }):lower()
-    if findany(lines, { 'vb_name', 'begin vb%.form', 'begin vb%.mdiform' }) then
-      vim.bo[bufnr].filetype = 'vb'
-    else
-      vim.bo[bufnr].filetype = 'form'
-    end
+    vim.bo[bufnr].filetype = 'form'
   end
 end
 
-function M.fs(path, bufnr) end
+-- Distinguish between Forth and F#.
+function M.fs(bufnr)
+  -- TODO: WIP
+  -- if vim.g.filetype_fs then
+  --   vim.bo[bufnr].filetype = vim.g.filetype_fs
+  --   return
+  -- end
+  -- local line = nextnonblank(bufnr, 1)
+  -- if findany(line, { '^%s*.?%( ', '^%s*\\G? ', '^\\$', '^%s*: %S' }) then
+  --   vim.bo[bufnr].filetype = 'forth'
+  -- else
+  --   vim.bo[bufnr].filetype = 'fsharp'
+  -- end
+end
 
 function M.header(bufnr)
   for _, line in ipairs(getlines(bufnr, 1, 200)) do
-    if findany(line, { '^@interface', '^@end', '^@class' }) then
+    if findany(line:lower(), { '^@interface', '^@end', '^@class' }) then
       if vim.g.c_syntax_for_h then
         vim.bo[bufnr].filetype = 'objc'
       else
@@ -171,11 +372,22 @@ function M.header(bufnr)
   end
 end
 
+function M.html(bufnr)
+  for _, line in ipairs(getlines(bufnr, 1, 10)) do
+    if matchregex(line, [[\<DTD\s\+XHTML\s]]) then
+      vim.bo[bufnr].filetype = 'xhtml'
+      return
+    elseif matchregex(line, [[\c{%\s*\(extends\|block\|load\)\>\|{#\s\+]]) then
+      vim.bo[bufnr].filetype = 'htmldjango'
+      return
+    end
+  end
+  vim.bo[bufnr].filetype = 'html'
+end
+
 function M.idl(bufnr)
   for _, line in ipairs(getlines(bufnr, 1, 50)) do
-    -- Always ignore case
-    line = line:lower()
-    if findany(line, { '^%s*import%s+"unknwn"%.idl', '^%s*import%s+"objidl"%.idl' }) then
+    if findany(line:lower(), { '^%s*import%s+"unknwn"%.idl', '^%s*import%s+"objidl"%.idl' }) then
       vim.bo[bufnr].filetype = 'msidl'
       return
     end
@@ -198,11 +410,83 @@ function M.inp(bufnr)
   end
 end
 
-function M.lpc(path, bufnr) end
+function M.lpc(bufnr)
+  if vim.g.lpc_syntax_for_c then
+    for _, line in ipairs(getlines(bufnr, 1, 12)) do
+      if
+        findany(line, {
+          '^//',
+          '^inherit',
+          '^private',
+          '^protected',
+          '^nosave',
+          '^string',
+          '^object',
+          '^mapping',
+          '^mixed',
+        })
+      then
+        vim.bo[bufnr].filetype = 'lpc'
+        return
+      end
+    end
+  end
+  vim.bo[bufnr].filetype = 'c'
+end
 
-function M.lprolog(path, bufnr) end
+function M.m(bufnr)
+  if vim.g.filetype_m then
+    vim.bo[bufnr].filetype = vim.g.filetype_m
+    return
+  end
 
-function M.m(path, bufnr) end
+  -- Excluding end(for|function|if|switch|while) common to Murphi
+  local octave_block_terminators =
+    [[\<end\%(_try_catch\|classdef\|enumeration\|events\|methods\|parfor\|properties\)\>]]
+  local objc_preprocessor = [[\c^\s*#\s*\%(import\|include\|define\|if\|ifn\=def\|undef\|line\|error\|pragma\)\>]]
+
+  -- Whether we've seen a multiline comment leader
+  local saw_comment = false
+  for _, line in ipairs(getlines(bufnr, 1, 100)) do
+    if line:find('^%s*/%*') then
+      -- /* ... */ is a comment in Objective C and Murphi, so we can't conclude
+      -- it's either of them yet, but track this as a hint in case we don't see
+      -- anything more definitive.
+      saw_comment = true
+    end
+    if line:find('^%s*//') or matchregex(line, [[\c^\s*@import\>]]) or matchregex(line, objc_preprocessor) then
+      vim.bo[bufnr].filetype = 'objc'
+      return
+    end
+    if
+      findany(line, { '^%s*#', '^%s*%%!' })
+      or matchregex(line, [[\c^\s*unwind_protect\>]])
+      or matchregex(line, [[\c\%(^\|;\)\s*]] .. octave_block_terminators)
+    then
+      vim.bo[bufnr].filetype = 'octave'
+      return
+    elseif line:find('^%s*%%') then
+      vim.bo[bufnr].filetype = 'matlab'
+      return
+    elseif line:find('^%s*%(%*') then
+      vim.bo[bufnr].filetype = 'mma'
+      return
+    elseif matchregex(line, [[\c^\s*\(\(type\|var\)\>\|--\)]]) then
+      vim.bo[bufnr].filetype = 'murphi'
+      return
+    end
+  end
+
+  if saw_comment then
+    -- We didn't see anything definitive, but this looks like either Objective C
+    -- or Murphi based on the comment leader. Assume the former as it is more
+    -- common.
+    vim.bo[bufnr].filetype = 'objc'
+  else
+    -- Default is Matlab
+    vim.bo[bufnr].filetype = 'matlab'
+  end
+end
 
 -- Rely on the file to start with a comment.
 -- MS message text files use ';', Sendmail files use '#' or 'dnl'
@@ -221,7 +505,15 @@ function M.mc(bufnr)
   vim.bo[bufnr].filetype = 'm4'
 end
 
-function M.mm(path, bufnr) end
+function M.mm(bufnr)
+  for _, line in ipairs(getlines(bufnr, 1, 20)) do
+    if matchregex(line, [[\c^\s*\(#\s*\(include\|import\)\>\|@import\>\|/\*\)]]) then
+      vim.bo[bufnr].filetype = 'objcpp'
+      return
+    end
+  end
+  vim.bo[bufnr].filetype = 'nroff'
+end
 
 function M.mms(bufnr)
   for _, line in ipairs(getlines(bufnr, 1, 20)) do
@@ -236,35 +528,129 @@ function M.mms(bufnr)
   vim.bo[bufnr].filetype = 'mmix'
 end
 
-function M.mod(path, bufnr) end
+-- Returns true if file content looks like LambdaProlog
+local function is_lprolog(bufnr)
+  -- Skip apparent comments and blank lines, what looks like
+  -- LambdaProlog comment may be RAPID header
+  for _, line in ipairs(getlines(bufnr, 1, -1)) do
+    -- The second pattern matches a LambdaProlog comment
+    if not findany(line, { '^%s*$', '^%s*%%' }) then
+      -- The pattern must not catch a go.mod file
+      return matchregex(line, [[\c\<module\s\+\w\+\s*\.\s*\(%\|$\)]]) ~= nil
+    end
+  end
+end
+
+-- Determine if *.mod is ABB RAPID, LambdaProlog, Modula-2, Modsim III or go.mod
+function M.mod(path, bufnr)
+  if vim.g.filetype_mod then
+    vim.bo[bufnr].filetype = vim.g.filetype_mod
+  elseif is_lprolog(bufnr) then
+    vim.bo[bufnr].filetype = 'lprolog'
+  elseif matchregex(nextnonblank(bufnr, 1), [[\%(\<MODULE\s\+\w\+\s*;\|^\s*(\*\)]]) then
+    vim.bo[bufnr].filetype = 'modula2'
+  elseif is_rapid(bufnr) then
+    vim.bo[bufnr].filetype = 'rapid'
+  elseif matchregex(path, [[\c\<go\.mod$]]) then
+    vim.bo[bufnr].filetype = 'gomod'
+  else
+    -- Nothing recognized, assume modsim3
+    vim.bo[bufnr].filetype = 'modsim3'
+  end
+end
 
 -- This function checks if one of the first five lines start with a dot. In
--- that case it is probably an nroff file: 'filetype' is set and 1 is returned.
+-- that case it is probably an nroff file: 'filetype' is set and true is returned.
 function M.nroff(bufnr)
   for _, line in ipairs(getlines(bufnr, 1, 5)) do
     if line:find('^%.') then
       vim.bo[bufnr].filetype = 'nroff'
-      return 1
+      return true
     end
   end
-  return 0
+  return false
 end
 
-function M.perl(path, bufnr) end
+-- If the file has an extension of 't' and is in a directory 't' or 'xt' then
+-- it is almost certainly a Perl test file.
+-- If the first line starts with '#' and contains 'perl' it's probably a Perl file.
+-- (Slow test) If a file contains a 'use' statement then it is almost certainly a Perl file.
+function M.perl(path, bufnr)
+  local dirname = vim.fn.expand(path, '%:p:h:t')
+  if vim.fn.expand(dirname, '%:e') == 't' and (dirname == 't' or dirname == 'xt') then
+    vim.bo[bufnr].filetype = 'perl'
+    return true
+  end
+  local first_line = getlines(bufnr, 1)
+  if first_line:find('^#') and first_line:lower():find('perl') then
+    vim.bo[bufnr].filetype = 'perl'
+    return true
+  end
+  for _, line in ipairs(getlines(bufnr, 1, 30)) do
+    if matchregex(line, [[\c^use\s\s*\k]]) then
+      vim.bo[bufnr].filetype = 'perl'
+      return true
+    end
+  end
+  return false
+end
 
 function M.pl(path, bufnr) end
 
-function M.pp(path, bufnr) end
+local pascal_comments = { '^%s*{', '^%s*%(*', '^%s*//' }
+local pascal_keywords = [[\c^\s*\%(program\|unit\|library\|uses\|begin\|procedure\|function\|const\|type\|var\)\>]]
+
+function M.pp(bufnr)
+  -- TODO: WIP
+
+  -- if vim.g.filetype_pp then
+  --   vim.bo[bufnr].filetype = vim.g.filetype_pp
+  --   return
+  -- end
+  -- local first_line = nextnonblank(bufnr, 1):lower()
+  -- if findany(first_line, { pascal_comments, pascal_keywords }) then
+  --   vim.bo[bufnr].filetype = "pascal"
+  -- else
+  --   vim.bo[bufnr].filetype = "puppet"
+  -- end
+end
+
+function M.prg(bufnr)
+  if vim.g.filetype_prg then
+    vim.bo[bufnr].filetype = vim.g.filetype_prg
+  elseif is_rapid(bufnr) then
+    vim.bo[bufnr].filetype = 'rapid'
+  else
+    -- Nothing recognized, assume Clipper
+    vim.bo[bufnr].filetype = 'clipper'
+  end
+end
 
-function M.prg(path, bufnr) end
+-- This function checks for an assembly comment in the first ten lines.
+-- If not found, assume Progress.
+function M.progress_asm(bufnr)
+  if vim.g.filetype_i then
+    vim.bo[bufnr].filetype = vim.g.filetype_i
+    return
+  end
 
-function M.progress_asm(path, bufnr) end
+  for _, line in ipairs(getlines(bufnr, 1, 10)) do
+    if line:find('^%s*;') or line:find('^/%*') then
+      return M.asm(bufnr)
+    elseif not line:find('^%s*$') or line:find('^/%*') then
+      -- Not an empty line: doesn't look like valid assembly code
+      -- or it looks like a Progress /* comment.
+      break
+    end
+  end
+  vim.bo[bufnr].filetype = 'progress'
+end
 
 function M.progress_cweb(bufnr)
   if vim.g.filetype_w then
     vim.bo[bufnr].filetype = vim.g.filetype_w
   else
-    if getlines(bufnr, 1):find('^&ANALYZE') or getlines(bufnr, 3):find('^&GLOBAL%-DEFINE') then
+    if getlines(bufnr, 1):lower():find('^&analyze') or getlines(bufnr, 3):lower():find('^&global%-define') then
       vim.bo[bufnr].filetype = 'progress'
     else
       vim.bo[bufnr].filetype = 'cweb'
@@ -272,15 +658,33 @@ function M.progress_cweb(bufnr)
   end
 end
 
-function M.progress_pascal(path, bufnr) end
+-- This function checks for valid Pascal syntax in the first 10 lines.
+-- Look for either an opening comment or a program start.
+-- If not found, assume Progress.
+function M.progress_pascal(bufnr)
+  if vim.g.filetype_p then
+    vim.bo[bufnr].filetype = vim.g.filetype_p
+    return
+  end
+  for _, line in ipairs(getlines(bufnr, 1, 10)) do
+    if findany(line, pascal_comments) or matchregex(line, pascal_keywords) then
+      vim.bo[bufnr].filetype = 'pascal'
+      return
+    elseif not line:find('^%s*$') or line:find('^/%*') then
+      -- Not an empty line: Doesn't look like valid Pascal code.
+      -- Or it looks like a Progress /* comment
+      break
+    end
+  end
+  vim.bo[bufnr].filetype = 'progress'
+end
 
 function M.proto(path, bufnr) end
 
 function M.r(bufnr)
   local lines = getlines(bufnr, 1, 50)
-  -- TODO: \< / \> which match the beginning / end of a word
   -- Rebol is easy to recognize, check for that first
-  if table.concat(lines):lower():find('rebol') then
+  if matchregex(table.concat(lines), [[\c\<rebol\>]]) then
     vim.bo[bufnr].filetype = 'rebol'
     return
   end
@@ -315,7 +719,43 @@ function M.redif(bufnr)
   end
 end
 
-function M.rules(path, bufnr) end
+local udev_rules_pattern = '^%s*udev_rules%s*=%s*"([%^"]+)/*".*'
+function M.rules(path, bufnr)
+  path = path:lower()
+  if
+    findany(path, {
+      '/etc/udev/.*%.rules$',
+      '/etc/udev/rules%.d/.*$.rules$',
+      '/usr/lib/udev/.*%.rules$',
+      '/usr/lib/udev/rules%.d/.*%.rules$',
+      '/lib/udev/.*%.rules$',
+      '/lib/udev/rules%.d/.*%.rules$',
+    })
+  then
+    vim.bo[bufnr].filetype = 'udevrules'
+  elseif path:find('^/etc/ufw/') then
+    -- Better than hog
+    vim.bo[bufnr].filetype = 'conf'
+  elseif findany(path, { '^/etc/polkit%-1/rules%.d', '/usr/share/polkit%-1/rules%.d' }) then
+    vim.bo[bufnr].filetype = 'javascript'
+  else
+    local ok, config_lines = pcall(vim.fn.readfile, '/etc/udev/udev.conf')
+    if not ok then
+      vim.bo[bufnr].filetype = 'hog'
+      return
+    end
+    local dir = vim.fn.expand(path, ':h')
+    for _, line in ipairs(config_lines) do
+      local match = line:match(udev_rules_pattern)
+      local udev_rules = line:gsub(udev_rules_pattern, match, 1)
+      if dir == udev_rules then
+        vim.bo[bufnr].filetype = 'udevrules'
+        return
+      end
+    end
+    vim.bo[bufnr].filetype = 'hog'
+  end
+end
 
 -- This function checks the first 25 lines of file extension "sc" to resolve
 -- detection between scala and SuperCollider
@@ -359,9 +799,27 @@ function M.sql(bufnr)
   end
 end
 
-function M.src(path, bufnr) end
+-- Determine if a *.src file is Kuka Robot Language
+function M.src(bufnr)
+  if vim.g.filetype_src then
+    vim.bo[bufnr].filetype = vim.g.filetype_src
+    return
+  end
+  local line = nextnonblank(bufnr, 1)
+  if matchregex(line, [[\c\v^\s*%(\&\w+|%(global\s+)?def%(fct)?>)]]) then
+    vim.bo[bufnr].filetype = 'krl'
+  end
+end
 
-function M.sys(path, bufnr) end
+function M.sys(bufnr)
+  if vim.g.filetype_sys then
+    vim.bo[bufnr].filetype = vim.g.filetype_sys
+  elseif is_rapid(bufnr) then
+    vim.bo[bufnr].filetype = 'rapid'
+  else
+    vim.bo[bufnr].filetype = 'bat'
+  end
+end
 
 function M.tex(path, bufnr) end
 
@@ -380,8 +838,8 @@ end
 
 function M.xml(bufnr)
   for _, line in ipairs(getlines(bufnr, 1, 100)) do
+    local is_docbook4 = line:find('<!DOCTYPE.*DocBook')
     line = line:lower()
-    local is_docbook4 = line:find('<!doctype.*docbook')
     local is_docbook5 = line:find([[ xmlns="http://docbook.org/ns/docbook"]])
     if is_docbook4 or is_docbook5 then
       vim.b[bufnr].docbk_type = 'xml'
@@ -403,10 +861,9 @@ function M.y(bufnr)
       vim.bo[bufnr].filetype = 'yacc'
       return
     end
-    -- TODO: in the Vim regex, \> is used to match the end of the word after "class",
-    -- can this be omitted?
-    if findany(line, { '^%s*#', '^%class', '^%s*#%s*include' }) then
+    if matchregex(line, [[\c^\s*\(#\|class\>\)]]) and not line:lower():find('^%s*#%s*include') then
       vim.bo[bufnr].filetype = 'racc'
+      return
     end
   end
   vim.bo[bufnr].filetype = 'yacc'
diff --git a/runtime/lua/vim/lsp/health.lua b/runtime/lua/vim/lsp/health.lua
index 74714ebc6b..bf8fe0932e 100644
--- a/runtime/lua/vim/lsp/health.lua
+++ b/runtime/lua/vim/lsp/health.lua
@@ -17,7 +17,8 @@ function M.check()
   local log_path = vim.lsp.get_log_path()
   report_info(string.format('Log path: %s', log_path))
 
-  local log_size = vim.loop.fs_stat(log_path).size
+  local log_file = vim.loop.fs_stat(log_path)
+  local log_size = log_file and log_file.size or 0
 
   local report_fn = (log_size / 1000000 > 100 and report_warn or report_info)
   report_fn(string.format('Log size: %d KB', log_size / 1000))