win: defaults: 'shellcmdflag', 'shellxquote' #7343

closes #7698

Wrapping a command in double-quotes allows cmd.exe to safely dequote the
entire command as if the user entered the entire command in an
interactive prompt. This reduces the need to escape nested and uneven
double quotes.

The `/s` flag of cmd.exe makes the behaviour more reliable:

    :set shellcmdflag=/s\ /c

Before this patch, cmd.exe cannot use cygwin echo.exe (as opposed to
cmd.exe `echo` builtin) even if it is wrapped in double quotes.

Example:
:: internal echo
> cmd /s /c " echo foo\:bar" "
foo\:bar"

:: cygwin echo.exe
> cmd /s /c " "echo" foo\:bar" "
foo:bar

5 files changed, 45 insertions, 15 deletions

diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 9ef5ccb5c5..f4bf49c7c5 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -5160,10 +5160,10 @@ A jump table for the options with a short description can be found at |Q_op|.
 	security reasons.
 
 						*'shellcmdflag'* *'shcf'*
-'shellcmdflag' 'shcf'	string	(default: "-c"; Windows: "/c")
+'shellcmdflag' 'shcf'	string	(default: "-c"; Windows: "/s /c")
 			global
 	Flag passed to the shell to execute "!" and ":!" commands; e.g.,
-	"bash.exe -c ls" or "cmd.exe /c dir".  For Windows
+	`bash.exe -c ls` or `cmd.exe /s /c "dir"`.  For Windows
 	systems, the default is set according to the value of 'shell', to
 	reduce the need to set this option by the user.
 	On Unix it can have more than one flag.  Each white space separated
@@ -5284,7 +5284,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 	to execute most external commands with cmd.exe.
 
 						*'shellxquote'* *'sxq'*
-'shellxquote' 'sxq'	string	(default: "")
+'shellxquote' 'sxq'	string	(default: "", Windows: "\"")
 			global
 	Quoting character(s), put around the command passed to the shell, for
 	the "!" and ":!" commands.  Includes the redirection.  See
diff --git a/src/nvim/options.lua b/src/nvim/options.lua
index 34ff810410..d653147943 100644
--- a/src/nvim/options.lua
+++ b/src/nvim/options.lua
@@ -2048,7 +2048,7 @@ return {
       varname='p_shcf',
       defaults={
         condition='WIN32',
-        if_true={vi="/c"},
+        if_true={vi="/s /c"},
         if_false={vi="-c"}
       }
     },
@@ -2104,7 +2104,11 @@ return {
       secure=true,
       vi_def=true,
       varname='p_sxq',
-      defaults={if_true={vi=""}}
+      defaults={
+        condition='WIN32',
+        if_true={vi="\""},
+        if_false={vi=""},
+      }
     },
     {
       full_name='shellxescape', abbreviation='sxe',
diff --git a/test/functional/eval/system_spec.lua b/test/functional/eval/system_spec.lua
index 446afefb59..201426c40b 100644
--- a/test/functional/eval/system_spec.lua
+++ b/test/functional/eval/system_spec.lua
@@ -120,33 +120,47 @@ describe('system()', function()
     end
   end)
 
-  describe('executes shell function if passed a string', function()
+  describe('executes shell function', function()
     local screen
 
     before_each(function()
-        clear()
-        screen = Screen.new()
-        screen:attach()
+      clear()
+      screen = Screen.new()
+      screen:attach()
     end)
 
     after_each(function()
-        screen:detach()
+      screen:detach()
     end)
 
     if iswin() then
+      local function test_more()
+        eq('root = true', eval([[get(split(system('"more" ".editorconfig"'), "\n"), 0, '')]]))
+      end
+      local function test_shell_unquoting()
+        eval([[system('"ping" "-n" "1" "127.0.0.1"')]])
+        eq(0, eval('v:shell_error'))
+        eq('"a b"\n', eval([[system('cmd /s/c "cmd /s/c "cmd /s/c "echo "a b""""')]]))
+        eq('"a b"\n', eval([[system('powershell -NoProfile -NoLogo -ExecutionPolicy RemoteSigned -Command echo ''\^"a b\^"''')]]))
+      end
+
       it('with shell=cmd.exe', function()
         command('set shell=cmd.exe')
         eq('""\n', eval([[system('echo ""')]]))
         eq('"a b"\n', eval([[system('echo "a b"')]]))
         eq('a \nb\n', eval([[system('echo a & echo b')]]))
         eq('a \n', eval([[system('echo a 2>&1')]]))
+        test_more()
         eval([[system('cd "C:\Program Files"')]])
         eq(0, eval('v:shell_error'))
+        test_shell_unquoting()
       end)
 
       it('with shell=cmd', function()
         command('set shell=cmd')
         eq('"a b"\n', eval([[system('echo "a b"')]]))
+        test_more()
+        test_shell_unquoting()
       end)
 
       it('with shell=$COMSPEC', function()
@@ -154,6 +168,8 @@ describe('system()', function()
         if comspecshell == 'cmd.exe' then
           command('set shell=$COMSPEC')
           eq('"a b"\n', eval([[system('echo "a b"')]]))
+          test_more()
+          test_shell_unquoting()
         else
           pending('$COMSPEC is not cmd.exe: ' .. comspecshell)
         end
@@ -187,7 +203,7 @@ describe('system()', function()
       ]])
     end)
 
-    it('`yes` and is interrupted with CTRL-C', function()
+    it('`yes` interrupted with CTRL-C', function()
       feed(':call system("' .. (iswin()
         and 'for /L %I in (1,0,2) do @echo y'
         or  'yes') .. '")<cr>')
@@ -239,6 +255,8 @@ describe('system()', function()
       end
     end)
     it('to backgrounded command does not crash', function()
+      -- cmd.exe doesn't background a command with &
+      if iswin() then return end
       -- This is indeterminate, just exercise the codepath. May get E5677.
       feed_command('call system("echo -n echoed &")')
       local v_errnum = string.match(eval("v:errmsg"), "^E%d*:")
@@ -254,6 +272,8 @@ describe('system()', function()
       eq("input", eval('system("cat -", "input")'))
     end)
     it('to backgrounded command does not crash', function()
+      -- cmd.exe doesn't background a command with &
+      if iswin() then return end
       -- This is indeterminate, just exercise the codepath. May get E5677.
       feed_command('call system("cat - &", "input")')
       local v_errnum = string.match(eval("v:errmsg"), "^E%d*:")
@@ -299,7 +319,7 @@ describe('system()', function()
     after_each(delete_file(fname))
 
     it('replaces NULs by SOH characters', function()
-      eq('part1\001part2\001part3\n', eval('system("cat '..fname..'")'))
+      eq('part1\001part2\001part3\n', eval([[system('"cat" "]]..fname..[["')]]))
     end)
   end)
 
@@ -366,7 +386,7 @@ describe('systemlist()', function()
     end
   end)
 
-  describe('exectues shell function', function()
+  describe('executes shell function', function()
     local screen
 
     before_each(function()
@@ -399,7 +419,7 @@ describe('systemlist()', function()
       ]])
     end)
 
-    it('`yes` and is interrupted with CTRL-C', function()
+    it('`yes` interrupted with CTRL-C', function()
       feed(':call systemlist("yes | xargs")<cr>')
       screen:expect([[
                                                              |
@@ -464,7 +484,7 @@ describe('systemlist()', function()
     after_each(delete_file(fname))
 
     it('replaces NULs by newline characters', function()
-      eq({'part1\npart2\npart3'}, eval('systemlist("cat '..fname..'")'))
+      eq({'part1\npart2\npart3'}, eval([[systemlist('"cat" "]]..fname..[["')]]))
     end)
   end)
 
diff --git a/test/functional/terminal/edit_spec.lua b/test/functional/terminal/edit_spec.lua
index d2b2d8a60c..84d7ae6e9c 100644
--- a/test/functional/terminal/edit_spec.lua
+++ b/test/functional/terminal/edit_spec.lua
@@ -36,6 +36,7 @@ describe(':edit term://*', function()
     local scr = get_screen(columns, lines)
     local rep = 'a'
     meths.set_option('shellcmdflag', 'REP ' .. rep)
+    command('set shellxquote=')  -- win: avoid extra quotes
     local rep_size = rep:byte()  -- 'a' => 97
     local sb = 10
     command('autocmd TermOpen * :setlocal scrollback='..tostring(sb)
diff --git a/test/functional/terminal/ex_terminal_spec.lua b/test/functional/terminal/ex_terminal_spec.lua
index 0a30b9bb02..4f22f7385d 100644
--- a/test/functional/terminal/ex_terminal_spec.lua
+++ b/test/functional/terminal/ex_terminal_spec.lua
@@ -8,6 +8,7 @@ local funcs = helpers.funcs
 local retry = helpers.retry
 local ok = helpers.ok
 local iswin = helpers.iswin
+local command = helpers.command
 
 describe(':terminal', function()
   local screen
@@ -143,6 +144,7 @@ describe(':terminal (with fake shell)', function()
   end)
 
   it('executes a given command through the shell', function()
+    command('set shellxquote=')   -- win: avoid extra quotes
     terminal_with_fake_shell('echo hi')
     screen:expect([[
       ^ready $ echo hi                                   |
@@ -154,6 +156,7 @@ describe(':terminal (with fake shell)', function()
 
   it("executes a given command through the shell, when 'shell' has arguments", function()
     nvim('set_option', 'shell', nvim_dir..'/shell-test -t jeff')
+    command('set shellxquote=')   -- win: avoid extra quotes
     terminal_with_fake_shell('echo hi')
     screen:expect([[
       ^jeff $ echo hi                                    |
@@ -164,6 +167,7 @@ describe(':terminal (with fake shell)', function()
   end)
 
   it('allows quotes and slashes', function()
+    command('set shellxquote=')   -- win: avoid extra quotes
     terminal_with_fake_shell([[echo 'hello' \ "world"]])
     screen:expect([[
       ^ready $ echo 'hello' \ "world"                    |
@@ -217,6 +221,7 @@ describe(':terminal (with fake shell)', function()
   end)
 
   it('works with gf', function()
+    command('set shellxquote=')   -- win: avoid extra quotes
     terminal_with_fake_shell([[echo "scripts/shadacat.py"]])
     screen:expect([[
       ^ready $ echo "scripts/shadacat.py"                |