python / python/cpython

make pyrepl more robust against crashes

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#122,468 2 comments 0 reactions 0 assignees View on GitHub

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topic-repl type-bug
Dominant language
Python
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Description

Bug report

Bug description:

This issue is motivated by a discussion with @serhiy-storchaka on #122456. Pyrepl/code.InteractiveInterpreter does not handle exceptions at various points, see the linked commend for an example.

Directly after writing this, I also got the following traceback that I now can't reproduce, by pressing ctrl-r then searching for a string, and then pressing ctrl-c at somehow the wrong point:

>>> Traceback (most recent call last):
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/simple_interact.py", line 147, in run_multiline_interactive_console
    statement = multiline_input(more_lines, ps1, ps2)
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/readline.py", line 385, in multiline_input
    return reader.readline()
           ~~~~~~~~~~~~~~~^^
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/reader.py", line 773, in readline
    self.handle1()
    ~~~~~~~~~~~~^^
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/reader.py", line 730, in handle1
    event = self.console.get_event(block)
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/unix_console.py", line 391, in get_event
    self.push_char(self.__read(1))
                   ~~~~~~~~~~~^^^
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/unix_console.py", line 203, in __read
    self.input_buffer = os.read(self.input_fd, 10000)
                        ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
KeyboardInterrupt

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/__main__.py", line 6, in <module>
    __pyrepl_interactive_console()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/main.py", line 59, in interactive_console
    run_multiline_interactive_console(console)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/simple_interact.py", line 164, in run_multiline_interactive_console
    r.pop_input_trans()
    ~~~~~~~~~~~~~~~~~^^
  File "/home/cfbolz/projects/cpython/Lib/_pyrepl/reader.py", line 546, in pop_input_trans
    self.input_trans = self.input_trans_stack.pop()
                       ~~~~~~~~~~~~~~~~~~~~~~~~~~^^
IndexError: pop from empty list

This crashed pyrepl. I think it would be better if we printed the exception, but then actually stayed in pyrepl, to make sure we don't lose the repl state which might have been annoying to get to.

Another way to crash pyrepl, but not the classic repl is to close sys.stderr and then raising an exception.

We could make pyrepl less crash-prone that by adding an except BaseException around the pyrepl loop in run_multiline_interactive_console.

Any opinions, @pablogsal, @ambv?

CPython versions tested on:

3.13, CPython main branch

Operating systems tested on:

Linux

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in Lib/_pyrepl/simple_interact.py at run_multiline_interactive_console, then trace the exception paths through reader.py and unix_console.py shown in the traceback. Reproduce the Ctrl-C/search failure and the closed-sys.stderr case. Done means pyrepl reports the exception and remains usable without losing the REPL state.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
cli
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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