From 5c84d12df104e976e8f56c43f9f975e54d9fd779 Mon Sep 17 00:00:00 2001
From: Aliaksei Budavei <0x000c70@gmail.com>
Date: Thu, 10 Apr 2025 21:52:14 +0200
Subject: [PATCH] runtime(filetype): make shell filetype detection more robust

closes: #17063

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 runtime/autoload/dist/ft.vim | 15 ++++++++-------
 runtime/syntax/sh.vim        | 11 ++++++++---
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index a740305226..4053e51f00 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -3,7 +3,7 @@ vim9script
 # Vim functions for file type detection
 #
 # Maintainer:		The Vim Project <https://github.com/vim/vim>
-# Last Change:		2025 Jan 25
+# Last Change:		2025 Apr 10
 # Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 # These functions are moved here from runtime/filetype.vim to make startup
@@ -875,16 +875,16 @@ export def SetFileTypeSH(name: string, setft = true): string
   if setft && expand("<amatch>") =~ g:ft_ignore_pat
     return ''
   endif
-  if name =~ '\<csh\>'
+  if name =~ '^csh$' || name =~ '^#!.\{-2,}\<csh\>'
     # Some .sh scripts contain #!/bin/csh.
     return SetFileTypeShell("csh", setft)
-  elseif name =~ '\<tcsh\>'
+  elseif name =~ '^tcsh$' || name =~ '^#!.\{-2,}\<tcsh\>'
     # Some .sh scripts contain #!/bin/tcsh.
     return SetFileTypeShell("tcsh", setft)
-  elseif name =~ '\<zsh\>'
+  elseif name =~ '^zsh$' || name =~ '^#!.\{-2,}\<zsh\>'
     # Some .sh scripts contain #!/bin/zsh.
     return SetFileTypeShell("zsh", setft)
-  elseif name =~ '\<ksh\>'
+  elseif name =~ '^ksh$' || name =~ '^#!.\{-2,}\<ksh\>'
     b:is_kornshell = 1
     if exists("b:is_bash")
       unlet b:is_bash
@@ -892,7 +892,8 @@ export def SetFileTypeSH(name: string, setft = true): string
     if exists("b:is_sh")
       unlet b:is_sh
     endif
-  elseif exists("g:bash_is_sh") || name =~ '\<bash\>' || name =~ '\<bash2\>'
+  elseif exists("g:bash_is_sh") || name =~ '^bash2\=$' ||
+	  \ name =~ '^#!.\{-2,}\<bash2\=\>'
     b:is_bash = 1
     if exists("b:is_kornshell")
       unlet b:is_kornshell
@@ -900,7 +901,7 @@ export def SetFileTypeSH(name: string, setft = true): string
     if exists("b:is_sh")
       unlet b:is_sh
     endif
-  elseif name =~ '\<sh\>' || name =~ '\<dash\>'
+  elseif name =~ '^\%(da\)\=sh$' || name =~ '^#!.\{-2,}\<\%(da\)\=sh\>'
     # Ubuntu links "sh" to "dash", thus it is expected to work the same way
     b:is_sh = 1
     if exists("b:is_kornshell")
diff --git a/runtime/syntax/sh.vim b/runtime/syntax/sh.vim
index 298198274e..9e5320f1ce 100644
--- a/runtime/syntax/sh.vim
+++ b/runtime/syntax/sh.vim
@@ -9,6 +9,7 @@
 "		2025 Jan 18 add bash coproc, remove duplicate syn keywords (#16467)
 "		2025 Mar 21 update shell capability detection (#16939)
 "		2025 Apr 03 command substitution opening paren at EOL (#17026)
+"		2025 Apr 10 improve shell detection (#17084)
 " Version:		208
 " Former URL:		http://www.drchip.org/astronaut/vim/index.html#SYNTAX_SH
 " For options and settings, please use:      :help ft-sh-syntax
@@ -23,11 +24,13 @@ endif
 let b:is_sh = 1
 
 " If the shell script itself specifies which shell to use, use it
-if getline(1) =~ '\<ksh\>'
+let s:shebang = getline(1)
+
+if s:shebang =~ '^#!.\{-2,}\<ksh\>'
  let b:is_kornshell = 1
-elseif getline(1) =~ '\<bash\>'
+elseif s:shebang =~ '^#!.\{-2,}\<bash\>'
  let b:is_bash      = 1
-elseif getline(1) =~ '\<dash\>'
+elseif s:shebang =~ '^#!.\{-2,}\<dash\>'
  let b:is_dash      = 1
 " handling /bin/sh with is_kornshell/is_sh {{{1
 " b:is_sh will be set when "#! /bin/sh" is found;
@@ -70,6 +73,8 @@ elseif !exists("b:is_kornshell") && !exists("b:is_bash") && !exists("b:is_posix"
  endif
 endif
 
+unlet s:shebang
+
 " if b:is_dash, set b:is_posix too
 if exists("b:is_dash")
  let b:is_posix= 1