fix #506

Author: windwp

lua/nvim-autopairs/utils.lua

@@ -161,6 +161,10 @@ M.text_sub_char = function(line, start, num)
     else
         finish = start + num - 1
     end
+
+    if start + finish < 0 then
+        return ""
+    end
     return string.sub(line, start, finish)
 end
 

tests/nvim-autopairs_spec.lua

@@ -7,6 +7,8 @@ _G.log = log
 local utils = require('nvim-autopairs.utils')
 _G.npairs = npairs;
 
+--  make test-file FILE=tests/nvim-autopairs_spec.lua
+
 -- use only = true to test 1 case
 -- stylua: ignore
 local data = {
@@ -833,6 +835,16 @@ local data = {
             '  test({',
         }
     },
+    {
+        name     = "89 <cr> key on markdown",
+        filetype = "markdown",
+        key      = [[<cr>]],
+        before   = [[|```python ]],
+        after    = {
+            "",
+            "|```python"
+        }
+    },
 }
 
 local run_data = _G.Test_filter(data)