fix(completion): make info/signature work with string array 'winborder'

Details:
- Should have been part of the previous `fix(ALL)` commit.

Author: echasnovski

lua/mini/completion.lua

@@ -690,7 +690,7 @@ H.keys = {
 }
 
 -- Flags for whether there is support for dedicated options
-H.has_winborder = vim.fn.has('nvim-0.11') == 1
+H.has_no_winborder = vim.fn.has('nvim-0.11') == 0
 H.has_pumborder = vim.fn.exists('+pumborder') == 1 -- Neovim>=0.12
 
 -- Caches for different actions -----------------------------------------------
@@ -1533,7 +1533,7 @@ end
 
 H.info_window_options = function()
   local win_config = H.get_config().window.info
-  local default_border = (H.has_winborder and vim.o.winborder ~= '') and vim.o.winborder or 'single'
+  local default_border = (H.has_no_winborder or vim.o.winborder == '') and 'single' or nil
   local border = win_config.border or default_border
   local pumborder = H.has_pumborder and vim.o.pumborder or ''
 
@@ -1709,7 +1709,7 @@ end
 
 H.signature_window_opts = function()
   local win_config = H.get_config().window.signature
-  local default_border = (H.has_winborder and vim.o.winborder ~= '') and vim.o.winborder or 'single'
+  local default_border = (H.has_no_winborder or vim.o.winborder == '') and 'single' or nil
   local border = win_config.border or default_border
   local lines = vim.api.nvim_buf_get_lines(H.signature.bufnr, 0, -1, false)
   local height, width = H.floating_dimensions(lines, win_config.height, win_config.width)

tests/test_completion.lua

@@ -1620,6 +1620,12 @@ T['Information window']["respects 'winborder' option"] = function()
   -- Should prefer explicitly configured value over 'winborder'
   child.lua('MiniCompletion.config.window.info.border = "double"')
   validate({ '╔', '═', '╗', '║', '╝', '═', '╚', '║' })
+
+  -- Should work with "string array" 'winborder'
+  if child.fn.has('nvim-0.12') == 0 then MiniTest.skip("String array 'winborder' is present on Neovim>=0.12") end
+  child.lua('MiniCompletion.config.window.info.border = nil')
+  child.o.winborder = '+,-,+,|,+,-,+,|'
+  validate({ '+', '-', '+', '|', '+', '-', '+', '|' })
 end
 
 T['Information window']["respects 'pumborder' option"] = function()
@@ -2031,6 +2037,12 @@ T['Signature help']["respects 'winborder' option"] = function()
   -- Should prefer explicitly configured value over 'winborder'
   child.lua('MiniCompletion.config.window.signature.border = "double"')
   validate({ '╔', '═', '╗', '║', '╝', '═', '╚', '║' })
+
+  -- Should work with "string array" 'winborder'
+  if child.fn.has('nvim-0.12') == 0 then MiniTest.skip("String array 'winborder' is present on Neovim>=0.12") end
+  child.lua('MiniCompletion.config.window.signature.border = nil')
+  child.o.winborder = '+,-,+,|,+,-,+,|'
+  validate({ '+', '-', '+', '|', '+', '-', '+', '|' })
 end
 
 T['Signature help']['triggers relevant events'] = function()