restored preview binary test using perl '-B'

lua/fzf-lua/previewer/builtin.lua

@@ -270,15 +270,13 @@ function Previewer.buffer_or_file:populate_preview_buf(entry_str)
     self.preview_bufloaded = true
     -- make sure the file is readable (or bad entry.path)
     if not vim.loop.fs_stat(entry.path) then return end
-    -- TODO: why does `file --dereference --mime` returns
-    -- wrong result for some lua files ('charset=binary')?
-    --[[ if utils.file_is_binary(entry.path) then
+    if utils.perl_file_is_binary(entry.path) then
       vim.api.nvim_buf_set_lines(self.preview_bufnr, 0, -1, false, {
         "Preview is not supported for binary files."
       })
       self:preview_buf_post(entry)
       return
-    end ]]
+    end
     -- enable syntax highlighting
     if self.syntax then
       if self.syntax_delay > 0 then

lua/fzf-lua/utils.lua

@@ -78,16 +78,32 @@ function M.sk_escape(str)
   end)
 end
 
+-- TODO: why does `file --dereference --mime` return
+-- wrong result for some lua files ('charset=binary')?
 M.file_is_binary = function(filepath)
   filepath = vim.fn.expand(filepath)
   if vim.fn.executable("file") ~= 1 or
      not vim.loop.fs_stat(filepath) then
     return false
   end
-  local out = M.io_system("file --dereference --mime " ..  filepath)
+  local out = M.io_system("file --dereference --mime " ..
+    vim.fn.shellescape(filepath))
   return out:match("charset=binary") ~= nil
 end
 
+M.perl_file_is_binary = function(filepath)
+  filepath = vim.fn.expand(filepath)
+  if vim.fn.executable("perl") ~= 1 or
+     not vim.loop.fs_stat(filepath) then
+    return false
+  end
+  -- can also use '-T' to test for text files
+  -- `perldoc -f -x` to learn more about '-B|-T'
+  M.io_system("perl -E 'exit((-B $ARGV[0])?0:1);' " ..
+    vim.fn.shellescape(filepath))
+  return not M.shell_error()
+end
+
 M.read_file = function(filepath)
   local fd = vim.loop.fs_open(filepath, "r", 438)
   if fd == nil then return '' end