fix: adjust indentation handling for Python 3.13+ built-in REPL

In Python 3.13 and later, the new REPL automatically adjusts indentation
based on context when entering a new line, which can cause unexpected
indentation errors when pasting pre-indented code.

This change enables/fixes compatibility by utilizing or working around
the new Paste Mode (F3) to disable auto-indentation and ensure smooth
execution of pasted blocks.

Author: Ky9oss

README.md

@@ -44,7 +44,7 @@ iron.setup {
         command = { "python3" },  -- or { "ipython", "--no-autoindent" }
         format = common.bracketed_paste_python,
         block_dividers = { "# %%", "#%%" },
-        env = {PYTHON_BASIC_REPL = "1"} --this is needed for python3.13 and up.
+        is_new_repl = true -- this must be set to true for Python 3.13 and later.
       }
     },
     -- set the file type of the newly created repl to ft

lua/iron/fts/common.lua

@@ -2,6 +2,7 @@ local is_windows = require("iron.util.os").is_windows
 local extend = require("iron.util.tables").extend
 local open_code = "\27[200~"
 local close_code = "\27[201~"
+local paste_mode_code = "\x1bOR"
 local cr = "\13"
 
 local common = {}
@@ -58,7 +59,11 @@ common.format = function(repldef, lines)
 
   -- passing the command is for python. this will not affect bracketed_paste.
   if repldef.format then
-    return repldef.format(lines, { command = repldef.command })
+    if repldef.is_new_repl then
+      return repldef.format(lines, { command = repldef.command, is_new_repl = repldef.is_new_repl })
+    else
+      return repldef.format(lines, { command = repldef.command })
+    end
   elseif #lines == 1 then
     new = lines
   else
@@ -98,6 +103,7 @@ common.bracketed_paste_python = function(lines, extras)
   local result = {}
 
   local cmd = extras["command"]
+  local is_new_repl = extras["is_new_repl"] or false
   local pseudo_meta = { current_buffer = vim.api.nvim_get_current_buf()}
   if type(cmd) == "function" then
     cmd = cmd(pseudo_meta)
@@ -155,6 +161,16 @@ common.bracketed_paste_python = function(lines, extras)
     table.insert(result, "\n")
   end
 
+  -- In Python 3.13 and later, the built-in REPL automatically 
+  -- adjusts indentation based on contextual information when 
+  -- a new line is entered. This behavior may cause unexpected 
+  -- indentation errors in some cases. Fortunately, the new 
+  -- REPL provides a Paste Mode, which disables automatic 
+  -- indentation and allows code to run smoothly.
+  if is_new_repl and not (is_windows and result[1] and result[1] == "\r") then
+    table.insert(result, 1, paste_mode_code)
+  end
+
   return result
 end
 

lua/iron/lowlevel.lua

@@ -6,6 +6,7 @@ local providers = require("iron.providers")
 local format = require("iron.fts.common").format
 local view = require("iron.view")
 local is_windows = require("iron.util.os").is_windows
+local paste_mode_code = "\x1bOR"
 
 --- Low level functions for iron
 -- This is needed to reduce the complexity of the user API functions.
@@ -191,6 +192,18 @@ ll.send_to_repl = function(meta, data)
     vim.fn.chansend(meta.job, dt)
   end
 
+  -- In Python 3.13 and later, the built-in REPL automatically 
+  -- adjusts indentation based on contextual information when 
+  -- a new line is entered. This behavior may cause unexpected 
+  -- indentation errors in some cases. Fortunately, the new 
+  -- REPL provides a Paste Mode, which disables automatic 
+  -- indentation and allows code to run smoothly.
+  if dt[1] and string.find(dt[1], paste_mode_code) then
+    vim.defer_fn(function()
+      vim.fn.chansend(meta.job, paste_mode_code .. "\r")
+    end, 200)
+  end
+
   if window ~= -1 then
     vim.api.nvim_win_set_cursor(window, {vim.api.nvim_buf_line_count(meta.bufnr), 0})
   end