refactor(runtime): port scripts.vim to lua (#18710)

4 files changed, 498 insertions, 99 deletions

diff --git a/runtime/doc/lua.txt b/runtime/doc/lua.txt
index 0e72e89672..3372bc90f7 100644
--- a/runtime/doc/lua.txt
+++ b/runtime/doc/lua.txt
@@ -2059,11 +2059,31 @@ add({filetypes})                                          *vim.filetype.add()*
                   })
 <
 
+                To add a fallback match on contents (see
+                |new-filetype-scripts|), use >
+
+                 vim.filetype.add {
+                   pattern = {
+                     ['.*'] = {
+                       priority = -math.huge,
+                       function(path, bufnr)
+                         local content = vim.filetype.getlines(bufnr, 1)
+                         if vim.filetype.matchregex(content, { [[^#!.*\<mine\>]] }) then
+                           return 'mine'
+                         elseif vim.filetype.matchregex(content, { [[\<drawing\>]] }) then
+                           return 'drawing'
+                         end
+                       end,
+                     },
+                   },
+                 }
+<
+
                 Parameters: ~
                     {filetypes}  (table) A table containing new filetype maps
                                  (see example).
 
-match({arg})                                            *vim.filetype.match()*
+match({args})                                           *vim.filetype.match()*
                 Perform filetype detection.
 
                 The filetype can be detected using one of three methods:
@@ -2096,22 +2116,22 @@ match({arg})                                            *vim.filetype.match()*
 <
 
                 Parameters: ~
-                    {arg}  (table) Table specifying which matching strategy to
-                           use. Accepted keys are:
-                           • buf (number): Buffer number to use for matching.
-                             Mutually exclusive with {contents}
-                           • filename (string): Filename to use for matching.
-                             When {buf} is given, defaults to the filename of
-                             the given buffer number. The file need not
-                             actually exist in the filesystem. When used
-                             without {buf} only the name of the file is used
-                             for filetype matching. This may result in failure
-                             to detect the filetype in cases where the
-                             filename alone is not enough to disambiguate the
-                             filetype.
-                           • contents (table): An array of lines representing
-                             file contents to use for matching. Can be used
-                             with {filename}. Mutually exclusive with {buf}.
+                    {args}  (table) Table specifying which matching strategy
+                            to use. Accepted keys are:
+                            • buf (number): Buffer number to use for matching.
+                              Mutually exclusive with {contents}
+                            • filename (string): Filename to use for matching.
+                              When {buf} is given, defaults to the filename of
+                              the given buffer number. The file need not
+                              actually exist in the filesystem. When used
+                              without {buf} only the name of the file is used
+                              for filetype matching. This may result in
+                              failure to detect the filetype in cases where
+                              the filename alone is not enough to disambiguate
+                              the filetype.
+                            • contents (table): An array of lines representing
+                              file contents to use for matching. Can be used
+                              with {filename}. Mutually exclusive with {buf}.
 
                 Return: ~
                     (string|nil) If a match was found, the matched filetype.
diff --git a/runtime/lua/vim/filetype.lua b/runtime/lua/vim/filetype.lua
index 8fe631e7ed..2874ea45e7 100644
--- a/runtime/lua/vim/filetype.lua
+++ b/runtime/lua/vim/filetype.lua
@@ -24,18 +24,26 @@ local function starsetf(ft, opts)
 end
 
 ---@private
---- Get a single line or line-range from the buffer.
+--- Get a single line or line range from the buffer.
+--- If only start_lnum is specified, return a single line as a string.
+--- If both start_lnum and end_lnum are omitted, return all lines from the buffer.
 ---
 ---@param bufnr number|nil The buffer to get the lines from
----@param start_lnum number The line number of the first line (inclusive, 1-based)
+---@param start_lnum number|nil The line number of the first line (inclusive, 1-based)
 ---@param end_lnum number|nil The line number of the last line (inclusive, 1-based)
 ---@return table<string>|string Array of lines, or string when end_lnum is omitted
 function M.getlines(bufnr, start_lnum, end_lnum)
-  if not end_lnum then
-    -- Return a single line as a string
+  if end_lnum then
+    -- Return a line range
+    return api.nvim_buf_get_lines(bufnr, start_lnum - 1, end_lnum, false)
+  end
+  if start_lnum then
+    -- Return a single line
     return api.nvim_buf_get_lines(bufnr, start_lnum - 1, start_lnum, false)[1] or ''
+  else
+    -- Return all lines
+    return api.nvim_buf_get_lines(bufnr, 0, -1, false)
   end
-  return api.nvim_buf_get_lines(bufnr, start_lnum - 1, end_lnum, false)
 end
 
 ---@private
@@ -600,7 +608,8 @@ local extension = {
   end,
   quake = 'm3quake',
   ['m4'] = function(path, bufnr)
-    return require('vim.filetype.detect').m4(path)
+    path = path:lower()
+    return not (path:find('html%.m4$') or path:find('fvwm2rc')) and 'm4'
   end,
   eml = 'mail',
   mk = 'make',
@@ -847,22 +856,22 @@ local extension = {
   sed = 'sed',
   sexp = 'sexplib',
   bash = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   ebuild = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   eclass = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   env = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr)
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr))
   end,
   ksh = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'ksh')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'ksh')
   end,
   sh = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr)
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr))
   end,
   sieve = 'sieve',
   siv = 'sieve',
@@ -1090,7 +1099,7 @@ local extension = {
     return require('vim.filetype.detect').scd(bufnr)
   end,
   tcsh = function(path, bufnr)
-    return require('vim.filetype.detect').shell(path, bufnr, 'tcsh')
+    return require('vim.filetype.detect').shell(path, M.getlines(bufnr), 'tcsh')
   end,
   sql = function(path, bufnr)
     return vim.g.filetype_sql and vim.g.filetype_sql or 'sql'
@@ -1510,40 +1519,40 @@ local filename = {
   ['/etc/serial.conf'] = 'setserial',
   ['/etc/udev/cdsymlinks.conf'] = 'sh',
   ['bash.bashrc'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   bashrc = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   ['.bashrc'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   ['.env'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr)
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr))
   end,
   ['.kshrc'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'ksh')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'ksh')
   end,
   ['.profile'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr)
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr))
   end,
   ['/etc/profile'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr)
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr))
   end,
   APKBUILD = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   PKGBUILD = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   ['.tcshrc'] = function(path, bufnr)
-    return require('vim.filetype.detect').shell(path, bufnr, 'tcsh')
+    return require('vim.filetype.detect').shell(path, M.getlines(bufnr), 'tcsh')
   end,
   ['tcsh.login'] = function(path, bufnr)
-    return require('vim.filetype.detect').shell(path, bufnr, 'tcsh')
+    return require('vim.filetype.detect').shell(path, M.getlines(bufnr), 'tcsh')
   end,
   ['tcsh.tcshrc'] = function(path, bufnr)
-    return require('vim.filetype.detect').shell(path, bufnr, 'tcsh')
+    return require('vim.filetype.detect').shell(path, M.getlines(bufnr), 'tcsh')
   end,
   ['/etc/slp.conf'] = 'slpconf',
   ['/etc/slp.reg'] = 'slpreg',
@@ -1934,28 +1943,28 @@ local pattern = {
   ['.*/etc/serial%.conf'] = 'setserial',
   ['.*/etc/udev/cdsymlinks%.conf'] = 'sh',
   ['%.bash[_%-]aliases'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   ['%.bash[_%-]logout'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   ['%.bash[_%-]profile'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   ['%.kshrc.*'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'ksh')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'ksh')
   end,
   ['%.profile.*'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr)
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr))
   end,
   ['.*/etc/profile'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr)
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr))
   end,
   ['bash%-fc[%-%.]'] = function(path, bufnr)
-    return require('vim.filetype.detect').sh(path, bufnr, 'bash')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'bash')
   end,
   ['%.tcshrc.*'] = function(path, bufnr)
-    return require('vim.filetype.detect').shell(path, bufnr, 'tcsh')
+    return require('vim.filetype.detect').sh(path, M.getlines(bufnr), 'tcsh')
   end,
   ['.*/etc/sudoers%.d/.*'] = starsetf('sudoers'),
   ['.*%._sst%.meta'] = 'sisu',
@@ -2165,6 +2174,25 @@ end
 ---  })
 --- </pre>
 ---
+--- To add a fallback match on contents (see |new-filetype-scripts|), use
+--- <pre>
+--- vim.filetype.add {
+---   pattern = {
+---     ['.*'] = {
+---       priority = -math.huge,
+---       function(path, bufnr)
+---         local content = vim.filetype.getlines(bufnr, 1)
+---         if vim.filetype.matchregex(content, { [[^#!.*\\<mine\\>]] }) then
+---           return 'mine'
+---         elseif vim.filetype.matchregex(content, { [[\\<drawing\\>]] }) then
+---           return 'drawing'
+---         end
+---       end,
+---     },
+---   },
+--- }
+--- </pre>
+---
 ---@param filetypes table A table containing new filetype maps (see example).
 function M.add(filetypes)
   for k, v in pairs(filetypes.extension or {}) do
@@ -2253,7 +2281,7 @@ end
 ---   vim.filetype.match({ contents = {'#!/usr/bin/env bash'} })
 --- </pre>
 ---
----@param arg table Table specifying which matching strategy to use. Accepted keys are:
+---@param args table Table specifying which matching strategy to use. Accepted keys are:
 ---                   * buf (number): Buffer number to use for matching. Mutually exclusive with
 ---                                   {contents}
 ---                   * filename (string): Filename to use for matching. When {buf} is given,
@@ -2270,22 +2298,18 @@ end
 ---@return function|nil A function that modifies buffer state when called (for example, to set some
 ---                     filetype specific buffer variables). The function accepts a buffer number as
 ---                     its only argument.
-function M.match(arg)
+function M.match(args)
   vim.validate({
-    arg = { arg, 't' },
+    arg = { args, 't' },
   })
 
-  if not (arg.buf or arg.filename or arg.contents) then
+  if not (args.buf or args.filename or args.contents) then
     error('At least one of "buf", "filename", or "contents" must be given')
   end
 
-  if arg.buf and arg.contents then
-    error('Only one of "buf" or "contents" must be given')
-  end
-
-  local bufnr = arg.buf
-  local name = arg.filename
-  local contents = arg.contents
+  local bufnr = args.buf
+  local name = args.filename
+  local contents = args.contents
 
   if bufnr and not name then
     name = api.nvim_buf_get_name(bufnr)
@@ -2297,13 +2321,6 @@ function M.match(arg)
 
   local ft, on_detect
 
-  if contents then
-    -- Sanity check: this should not happen
-    assert(not bufnr, '"buf" and "contents" are mutually exclusive')
-    -- TODO: "scripts.lua" content matching
-    return
-  end
-
   -- First check for the simple case where the full path exists as a key
   local path = vim.fn.resolve(vim.fn.fnamemodify(name, ':p'))
   ft, on_detect = dispatch(filename[path], path, bufnr)
@@ -2345,7 +2362,7 @@ function M.match(arg)
     return ft, on_detect
   end
 
-  -- Finally, check patterns with negative priority
+  -- Next, check patterns with negative priority
   for i = j, #pattern_sorted do
     local v = pattern_sorted[i]
     local k = next(v)
@@ -2359,6 +2376,19 @@ function M.match(arg)
       end
     end
   end
+
+  -- Finally, check file contents
+  if contents or bufnr then
+    contents = contents or M.getlines(bufnr)
+    -- If name is nil, catch any errors from the contents filetype detection function.
+    -- If the function tries to use the filename that is nil then it will fail,
+    -- but this enables checks which do not need a filename to still work.
+    local ok
+    ok, ft = pcall(require('vim.filetype.detect').match_contents, contents, name)
+    if ok and ft then
+      return ft
+    end
+  end
 end
 
 return M
diff --git a/runtime/lua/vim/filetype/detect.lua b/runtime/lua/vim/filetype/detect.lua
index 14a4381835..37922b4ebf 100644
--- a/runtime/lua/vim/filetype/detect.lua
+++ b/runtime/lua/vim/filetype/detect.lua
@@ -206,12 +206,52 @@ function M.csh(path, bufnr)
     -- Filetype was already detected
     return
   end
+  local contents = getlines(bufnr)
   if vim.g.filetype_csh then
-    return M.shell(path, bufnr, vim.g.filetype_csh)
+    return M.shell(path, contents, vim.g.filetype_csh)
   elseif string.find(vim.o.shell, 'tcsh') then
-    return M.shell(path, bufnr, 'tcsh')
+    return M.shell(path, contents, 'tcsh')
   else
-    return M.shell(path, bufnr, 'csh')
+    return M.shell(path, contents, 'csh')
+  end
+end
+
+local function cvs_diff(path, contents)
+  for _, line in ipairs(contents) do
+    if not line:find('^%? ') then
+      if matchregex(line, [[^Index:\s\+\f\+$]]) then
+        -- CVS diff
+        return 'diff'
+      elseif
+        -- Locale input files: Formal Definitions of Cultural Conventions
+        -- Filename must be like en_US, fr_FR@euro or en_US.UTF-8
+        findany(path, { '%a%a_%a%a$', '%a%a_%a%a[%.@]', '%a%a_%a%ai18n$', '%a%a_%a%aPOSIX$', '%a%a_%a%atranslit_' })
+      then
+        -- Only look at the first 100 lines
+        for line_nr = 1, 100 do
+          if not contents[line_nr] then
+            break
+          elseif
+            findany(contents[line_nr], {
+              '^LC_IDENTIFICATION$',
+              '^LC_CTYPE$',
+              '^LC_COLLATE$',
+              '^LC_MONETARY$',
+              '^LC_NUMERIC$',
+              '^LC_TIME$',
+              '^LC_MESSAGES$',
+              '^LC_PAPER$',
+              '^LC_TELEPHONE$',
+              '^LC_MEASUREMENT$',
+              '^LC_NAME$',
+              '^LC_ADDRESS$',
+            })
+          then
+            return 'fdcc'
+          end
+        end
+      end
+    end
   end
 end
 
@@ -270,6 +310,38 @@ function M.dep3patch(path, bufnr)
   end
 end
 
+local function diff(contents)
+  if
+    contents[1]:find('^%-%-%- ') and contents[2]:find('^%+%+%+ ')
+    or contents[1]:find('^%* looking for ') and contents[2]:find('^%* comparing to ')
+    or contents[1]:find('^%*%*%* ') and contents[2]:find('^%-%-%- ')
+    or contents[1]:find('^=== ') and ((contents[2]:find('^' .. string.rep('=', 66)) and contents[3]:find('^%-%-% ') and contents[4]:find(
+      '^%+%+%+'
+    )) or (contents[2]:find('^%-%-%- ') and contents[3]:find('^%+%+%+ ')))
+    or findany(contents[1], { '^=== removed', '^=== added', '^=== renamed', '^=== modified' })
+  then
+    return 'diff'
+  end
+end
+
+function M.dns_zone(contents)
+  if
+    findany(
+      contents[1] .. contents[2] .. contents[3] .. contents[4],
+      { '^; <<>> DiG [0-9%.]+.* <<>>', '%$ORIGIN', '%$TTL', 'IN%s+SOA' }
+    )
+  then
+    return 'bindzone'
+  end
+  -- BAAN
+  if -- Check for 1 to 80 '*' characters
+    contents[1]:find('|%*' .. string.rep('%*?', 79)) and contents[2]:find('VRC ')
+    or contents[2]:find('|%*' .. string.rep('%*?', 79)) and contents[3]:find('VRC ')
+  then
+    return 'baan'
+  end
+end
+
 function M.dtrace(bufnr)
   if vim.fn.did_filetype() ~= 0 then
     -- Filetype was already detected
@@ -483,7 +555,7 @@ function M.install(path, bufnr)
   if getlines(bufnr, 1):lower():find('<%?php') then
     return 'php'
   end
-  return M.sh(path, bufnr, 'bash')
+  return M.sh(path, getlines(bufnr), 'bash')
 end
 
 -- Innovation Data Processing
@@ -572,10 +644,15 @@ function M.m(bufnr)
   end
 end
 
-function M.m4(path)
-  path = path:lower()
-  if not path:find('html%.m4$') and not path:find('fvwm2rc') then
-    return 'm4'
+local function m4(contents)
+  for _, line in ipairs(contents) do
+    if matchregex(line, [[^\s*dnl\>]]) then
+      return 'm4'
+    end
+  end
+  if vim.env.TERM == 'amiga' and findany(contents[1]:lower(), { '^;', '^%.bra' }) then
+    -- AmigaDos scripts
+    return 'amiga'
   end
 end
 
@@ -625,7 +702,7 @@ end
 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
+  for _, line in ipairs(getlines(bufnr)) do
     -- The second pattern matches a LambdaProlog comment
     if not findany(line, { '^%s*$', '^%s*%%' }) then
       -- The pattern must not catch a go.mod file
@@ -982,24 +1059,26 @@ function M.sgml(bufnr)
   end
 end
 
-function M.sh(path, bufnr, name)
-  if vim.fn.did_filetype() ~= 0 or path:find(vim.g.ft_ignore_pat) then
+function M.sh(path, contents, name)
+  -- Path may be nil, do not fail in that case
+  if vim.fn.did_filetype() ~= 0 or (path or ''):find(vim.g.ft_ignore_pat) then
     -- Filetype was already detected or detection should be skipped
     return
   end
 
   local on_detect
 
-  name = name or getlines(bufnr, 1)
+  -- Get the name from the first line if not specified
+  name = name or contents[1]
   if matchregex(name, [[\<csh\>]]) then
     -- Some .sh scripts contain #!/bin/csh.
-    return M.shell(path, bufnr, 'csh')
+    return M.shell(path, contents, 'csh')
     -- Some .sh scripts contain #!/bin/tcsh.
   elseif matchregex(name, [[\<tcsh\>]]) then
-    return M.shell(path, bufnr, 'tcsh')
+    return M.shell(path, contents, 'tcsh')
     -- Some .sh scripts contain #!/bin/zsh.
   elseif matchregex(name, [[\<zsh\>]]) then
-    return M.shell(path, bufnr, 'zsh')
+    return M.shell(path, contents, 'zsh')
   elseif matchregex(name, [[\<ksh\>]]) then
     on_detect = function(b)
       vim.b[b].is_kornshell = 1
@@ -1019,27 +1098,30 @@ function M.sh(path, bufnr, name)
       vim.b[b].is_bash = nil
     end
   end
-  return M.shell(path, bufnr, 'sh'), on_detect
+  return M.shell(path, contents, 'sh'), on_detect
 end
 
 -- For shell-like file types, check for an "exec" command hidden in a comment, as used for Tcl.
--- Also called from scripts.vim, thus can't be local to this script. [TODO]
-function M.shell(path, bufnr, name)
+function M.shell(path, contents, name)
   if vim.fn.did_filetype() ~= 0 or matchregex(path, vim.g.ft_ignore_pat) then
     -- Filetype was already detected or detection should be skipped
     return
   end
+
   local prev_line = ''
-  for _, line in ipairs(getlines(bufnr, 2, -1)) do
-    line = line:lower()
-    if line:find('%s*exec%s') and not prev_line:find('^%s*#.*\\$') then
-      -- Found an "exec" line after a comment with continuation
-      local n = line:gsub('%s*exec%s+([^ ]*/)?', '', 1)
-      if matchregex(n, [[\c\<tclsh\|\<wish]]) then
-        return 'tcl'
+  for line_nr, line in ipairs(contents) do
+    -- Skip the first line
+    if line_nr ~= 1 then
+      line = line:lower()
+      if line:find('%s*exec%s') and not prev_line:find('^%s*#.*\\$') then
+        -- Found an "exec" line after a comment with continuation
+        local n = line:gsub('%s*exec%s+([^ ]*/)?', '', 1)
+        if matchregex(n, [[\c\<tclsh\|\<wish]]) then
+          return 'tcl'
+        end
       end
+      prev_line = line
     end
-    prev_line = line
   end
   return name
 end
@@ -1123,7 +1205,7 @@ end
 
 -- Determine if a *.tf file is TF mud client or terraform
 function M.tf(bufnr)
-  for _, line in ipairs(getlines(bufnr, 1, -1)) do
+  for _, line in ipairs(getlines(bufnr)) do
     -- Assume terraform file on a non-empty line (not whitespace-only)
     -- and when the first non-whitespace character is not a ; or /
     if not line:find('^%s*$') and not line:find('^%s*[;/]') then
@@ -1204,4 +1286,271 @@ end
 -- luacheck: pop
 -- luacheck: pop
 
+local patterns_hashbang = {
+  ['^zsh\\>'] = { 'zsh', { vim_regex = true } },
+  ['^\\(tclsh\\|wish\\|expectk\\|itclsh\\|itkwish\\)\\>'] = { 'tcl', { vim_regex = true } },
+  ['^expect\\>'] = { 'expect', { vim_regex = true } },
+  ['^gnuplot\\>'] = { 'gnuplot', { vim_regex = true } },
+  ['make\\>'] = { 'make', { vim_regex = true } },
+  ['^pike\\%(\\>\\|[0-9]\\)'] = { 'pike', { vim_regex = true } },
+  lua = 'lua',
+  perl = 'perl',
+  php = 'php',
+  python = 'python',
+  ['^groovy\\>'] = { 'groovy', { vim_regex = true } },
+  raku = 'raku',
+  ruby = 'ruby',
+  ['node\\(js\\)\\=\\>\\|js\\>'] = { 'javascript', { vim_regex = true } },
+  ['rhino\\>'] = { 'javascript', { vim_regex = true } },
+  -- BC calculator
+  ['^bc\\>'] = { 'bc', { vim_regex = true } },
+  ['sed\\>'] = { 'sed', { vim_regex = true } },
+  ocaml = 'ocaml',
+  -- Awk scripts; also finds "gawk"
+  ['awk\\>'] = { 'awk', { vim_regex = true } },
+  wml = 'wml',
+  scheme = 'scheme',
+  cfengine = 'cfengine',
+  escript = 'erlang',
+  haskell = 'haskell',
+  clojure = 'clojure',
+  ['scala\\>'] = { 'scala', { vim_regex = true } },
+  -- Free Pascal
+  ['instantfpc\\>'] = { 'pascal', { vim_regex = true } },
+  ['fennel\\>'] = { 'fennel', { vim_regex = true } },
+  -- MikroTik RouterOS script
+  ['rsc\\>'] = { 'routeros', { vim_regex = true } },
+  ['fish\\>'] = { 'fish', { vim_regex = true } },
+  ['gforth\\>'] = { 'forth', { vim_regex = true } },
+  ['icon\\>'] = { 'icon', { vim_regex = true } },
+}
+
+---@private
+-- File starts with "#!".
+local function match_from_hashbang(contents, path)
+  local first_line = contents[1]
+  -- Check for a line like "#!/usr/bin/env {options} bash".  Turn it into
+  -- "#!/usr/bin/bash" to make matching easier.
+  -- Recognize only a few {options} that are commonly used.
+  if matchregex(first_line, [[^#!\s*\S*\<env\s]]) then
+    first_line = first_line:gsub('%S+=%S+', '')
+    first_line = first_line
+      :gsub('%-%-ignore%-environment', '', 1)
+      :gsub('%-%-split%-string', '', 1)
+      :gsub('%-[iS]', '', 1)
+    first_line = vim.fn.substitute(first_line, [[\<env\s\+]], '', '')
+  end
+
+  -- Get the program name.
+  -- Only accept spaces in PC style paths: "#!c:/program files/perl [args]".
+  -- If the word env is used, use the first word after the space:
+  -- "#!/usr/bin/env perl [path/args]"
+  -- If there is no path use the first word: "#!perl [path/args]".
+  -- Otherwise get the last word after a slash: "#!/usr/bin/perl [path/args]".
+  local name
+  if first_line:find('^#!%s*%a:[/\\]') then
+    name = vim.fn.substitute(first_line, [[^#!.*[/\\]\(\i\+\).*]], '\\1', '')
+  elseif matchregex(first_line, [[^#!.*\<env\>]]) then
+    name = vim.fn.substitute(first_line, [[^#!.*\<env\>\s\+\(\i\+\).*]], '\\1', '')
+  elseif matchregex(first_line, [[^#!\s*[^/\\ ]*\>\([^/\\]\|$\)]]) then
+    name = vim.fn.substitute(first_line, [[^#!\s*\([^/\\ ]*\>\).*]], '\\1', '')
+  else
+    name = vim.fn.substitute(first_line, [[^#!\s*\S*[/\\]\(\i\+\).*]], '\\1', '')
+  end
+
+  -- tcl scripts may have #!/bin/sh in the first line and "exec wish" in the
+  -- third line. Suggested by Steven Atkinson.
+  if contents[3] and contents[3]:find('^exec wish') then
+    name = 'wish'
+  end
+
+  if matchregex(name, [[^\(bash\d*\|\|ksh\d*\|sh\)\>]]) then
+    -- Bourne-like shell scripts: bash bash2 ksh ksh93 sh
+    return require('vim.filetype.detect').sh(path, contents, first_line)
+  elseif matchregex(name, [[^csh\>]]) then
+    return require('vim.filetype.detect').shell(path, contents, vim.g.filetype_csh or 'csh')
+  elseif matchregex(name, [[^tcsh\>]]) then
+    return require('vim.filetype.detect').shell(path, contents, 'tcsh')
+  end
+
+  for k, v in pairs(patterns_hashbang) do
+    local ft = type(v) == 'table' and v[1] or v
+    local opts = type(v) == 'table' and v[2] or {}
+    if opts.vim_regex and matchregex(name, k) or name:find(k) then
+      return ft
+    end
+  end
+end
+
+local patterns_text = {
+  ['^#compdef\\>'] = { 'zsh', { vim_regex = true } },
+  ['^#autoload\\>'] = { 'zsh', { vim_regex = true } },
+  -- ELM Mail files
+  ['^From [a-zA-Z][a-zA-Z_0-9%.=%-]*(@[^ ]*)? .* 19%d%d$'] = 'mail',
+  ['^From [a-zA-Z][a-zA-Z_0-9%.=%-]*(@[^ ]*)? .* 20%d%d$'] = 'mail',
+  ['^From %- .* 19%d%d$'] = 'mail',
+  ['^From %- .* 20%d%d$'] = 'mail',
+  -- Mason
+  ['^<[%%&].*>'] = 'mason',
+  -- Vim scripts (must have '" vim' as the first line to trigger this)
+  ['^" *[vV]im$['] = 'vim',
+  -- libcxx and libstdc++ standard library headers like ["iostream["] do not have
+  -- an extension, recognize the Emacs file mode.
+  ['%-%*%-.*[cC]%+%+.*%-%*%-'] = 'cpp',
+  ['^\\*\\* LambdaMOO Database, Format Version \\%([1-3]\\>\\)\\@!\\d\\+ \\*\\*$'] = {
+    'moo',
+    { vim_regex = true },
+  },
+  -- Diff file:
+  -- - "diff" in first line (context diff)
+  -- - "Only in " in first line
+  -- - "--- " in first line and "+++ " in second line (unified diff).
+  -- - "*** " in first line and "--- " in second line (context diff).
+  -- - "# It was generated by makepatch " in the second line (makepatch diff).
+  -- - "Index: <filename>" in the first line (CVS file)
+  -- - "=== ", line of "=", "---", "+++ " (SVK diff)
+  -- - "=== ", "--- ", "+++ " (bzr diff, common case)
+  -- - "=== (removed|added|renamed|modified)" (bzr diff, alternative)
+  -- - "# HG changeset patch" in first line (Mercurial export format)
+  ['^\\(diff\\>\\|Only in \\|\\d\\+\\(,\\d\\+\\)\\=[cda]\\d\\+\\>\\|# It was generated by makepatch \\|Index:\\s\\+\\f\\+\\r\\=$\\|===== \\f\\+ \\d\\+\\.\\d\\+ vs edited\\|==== //\\f\\+#\\d\\+\\|# HG changeset patch\\)'] = {
+    'diff',
+    { vim_regex = true },
+  },
+  function(contents)
+    return diff(contents)
+  end,
+  -- PostScript Files (must have %!PS as the first line, like a2ps output)
+  ['^%%![ \t]*PS'] = 'postscr',
+  function(contents)
+    return m4(contents)
+  end,
+  -- SiCAD scripts (must have procn or procd as the first line to trigger this)
+  ['^ *proc[nd] *$'] = { 'sicad', { ignore_case = true } },
+  ['^%*%*%*%*  Purify'] = 'purifylog',
+  -- XML
+  ['<%?%s*xml.*%?>'] = 'xml',
+  -- XHTML (e.g.: PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN")
+  ['\\<DTD\\s\\+XHTML\\s'] = 'xhtml',
+  -- HTML (e.g.: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN")
+  -- Avoid "doctype html", used by slim.
+  ['\\c<!DOCTYPE\\s\\+html\\>'] = { 'html', { vim_regex = true } },
+  -- PDF
+  ['^%%PDF%-'] = 'pdf',
+  -- XXD output
+  ['^%x%x%x%x%x%x%x: %x%x ?%x%x ?%x%x ?%x%x '] = 'xxd',
+  -- RCS/CVS log output
+  ['^RCS file:'] = { 'rcslog', { start_lnum = 1, end_lnum = 2 } },
+  -- CVS commit
+  ['^CVS:'] = { 'cvs', { start_lnum = 2 } },
+  ['^CVS: '] = { 'cvs', { start_lnum = -1 } },
+  -- Prescribe
+  ['^!R!'] = 'prescribe',
+  -- Send-pr
+  ['^SEND%-PR:'] = 'sendpr',
+  -- SNNS files
+  ['^SNNS network definition file'] = 'snnsnet',
+  ['^SNNS pattern definition file'] = 'snnspat',
+  ['^SNNS result file'] = 'snnsres',
+  ['^%%.-[Vv]irata'] = { 'virata', { start_lnum = 1, end_lnum = 5 } },
+  ['[0-9:%.]* *execve%('] = 'strace',
+  ['^__libc_start_main'] = 'strace',
+  -- VSE JCL
+  ['^\\* $$ JOB\\>'] = { 'vsejcl', { vim_regex = true } },
+  ['^// *JOB\\>'] = { 'vsejcl', { vim_regex = true } },
+  -- TAK and SINDA
+  ['K & K  Associates'] = { 'takout', { start_lnum = 4 } },
+  ['TAK 2000'] = { 'takout', { start_lnum = 2 } },
+  ['S Y S T E M S   I M P R O V E D '] = { 'syndaout', { start_lnum = 3 } },
+  ['Run Date: '] = { 'takcmp', { start_lnum = 6 } },
+  ['Node    File  1'] = { 'sindacmp', { start_lnum = 9 } },
+  function(contents)
+    require('vim.filetype.detect').dns_zone(contents)
+  end,
+  -- Valgrind
+  ['^==%d+== valgrind'] = 'valgrind',
+  ['^==%d+== Using valgrind'] = { 'valgrind', { start_lnum = 3 } },
+  -- Go docs
+  ['PACKAGE DOCUMENTATION$'] = 'godoc',
+  -- Renderman Interface Bytestream
+  ['^##RenderMan'] = 'rib',
+  -- Scheme scripts
+  ['exec%s%+%S*scheme'] = { 'scheme', { start_lnum = 1, end_lnum = 2 } },
+  -- Git output
+  ['^\\(commit\\|tree\\|object\\) \\x\\{40,\\}\\>\\|^tag \\S\\+$'] = { 'git', { vim_regex = true } },
+  function(lines)
+    -- Gprof (gnu profiler)
+    if lines[1] == 'Flat profile:' and lines[2] == '' and lines[3]:find('^Each sample counts as .* seconds%.$') then
+      return 'gprof'
+    end
+  end,
+  -- Erlang terms
+  -- (See also: http://www.gnu.org/software/emacs/manual/html_node/emacs/Choosing-Modes.html#Choosing-Modes)
+  ['%-%*%-.*erlang.*%-%*%-'] = { 'erlang', { ignore_case = true } },
+  -- YAML
+  ['^%%YAML'] = 'yaml',
+  -- MikroTik RouterOS script
+  ['^#.*by RouterOS'] = 'routeros',
+  -- Sed scripts
+  -- #ncomment is allowed but most likely a false positive so require a space before any trailing comment text
+  ['^#n%s'] = 'sed',
+  ['^#n$'] = 'sed',
+}
+
+---@private
+-- File does not start with "#!".
+local function match_from_text(contents, path)
+  if contents[1]:find('^:$') then
+    -- Bourne-like shell scripts: sh ksh bash bash2
+    return M.sh(path, contents)
+  elseif matchregex('\n' .. table.concat(contents, '\n'), [[\n\s*emulate\s\+\%(-[LR]\s\+\)\=[ckz]\=sh\>]]) then
+    -- Z shell scripts
+    return 'zsh'
+  end
+
+  for k, v in pairs(patterns_text) do
+    if type(v) == 'string' then
+      -- Check the first line only
+      if contents[1]:find(k) then
+        return v
+      end
+    elseif type(v) == 'function' then
+      -- If filetype detection fails, continue with the next pattern
+      local ok, ft = pcall(v, contents)
+      if ok and ft then
+        return ft
+      end
+    else
+      local opts = type(v) == 'table' and v[2] or {}
+      if opts.start_lnum and opts.end_lnum then
+        assert(not opts.ignore_case, 'ignore_case=true is ignored when start_lnum is also present, needs refactor')
+        for i = opts.start_lnum, opts.end_lnum do
+          if not contents[i] then
+            break
+          elseif contents[i]:find(k) then
+            return v[1]
+          end
+        end
+      else
+        local line_nr = opts.start_lnum == -1 and #contents or opts.start_lnum or 1
+        if contents[line_nr] then
+          local line = opts.ignore_case and contents[line_nr]:lower() or contents[line_nr]
+          if opts.vim_regex and matchregex(line, k) or line:find(k) then
+            return v[1]
+          end
+        end
+      end
+    end
+  end
+  return cvs_diff(path, contents)
+end
+
+M.match_contents = function(contents, path)
+  local first_line = contents[1]
+  if first_line:find('^#!') then
+    return match_from_hashbang(contents, path)
+  else
+    return match_from_text(contents, path)
+  end
+end
+
 return M
diff --git a/runtime/scripts.vim b/runtime/scripts.vim
index 36763a4a82..49e9e259a2 100644
--- a/runtime/scripts.vim
+++ b/runtime/scripts.vim
@@ -11,9 +11,9 @@
 " 'ignorecase' option making a difference.  Where case is to be ignored use
 " =~? instead.  Do not use =~ anywhere.
 
-
-" Only do the rest when the FileType autocommand has not been triggered yet.
-if did_filetype()
+" Only do the rest when not using Lua filetype detection
+" and the FileType autocommand has not been triggered yet.
+if exists("g:do_filetype_lua") && g:do_filetype_lua || did_filetype()
   finish
 endif