pytest-dev__pytest-5262

Leaderboard / pytest-5262

pytest-dev/pytest · v4.5 · 6 steps · 53,852 tokens · 113s

resolved

1.00

⬤ Audit flag — broken-tests

1 of 109 test ids are corrupt - pytest progress-bar output was captured as a test id: '[100%]'. pytest aborts the whole run on an unknown id, so the task would falsely score 0; the harness quarantines them before scoring.

what does this mean? →

The task

The bug report the agent was given — plus the gold fix and hidden tests, shown here for reference. The agent saw only the problem statement.

Problem statementgithub issue

_pytest.capture.EncodedFile mode should not include `b` (binary)
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- [x] a detailed description of the bug or suggestion

Exception when youtube-dl logs to pytest captured output. Youtube-dl looks for `b` in `out.mode` to decide whether to writes `bytes` or `str`. `_pytest.capture.EncodedFile` incorrectly advertises `rb+`, the mode of the underlying stream. Its `write()` method raises an exception when passed `bytes`.

```
(pytest-issue-ve3) 01:11:48:nlevitt@Internets-Air-2:/tmp$ py.test test.py 
============================================================================== test session starts …

Gold patchheld back · the reference fix

diff --git a/src/_pytest/capture.py b/src/_pytest/capture.py--- a/src/_pytest/capture.py+++ b/src/_pytest/capture.py@@ -447,6 +447,10 @@ def name(self): """Ensure that file.name is a string.""" return repr(self.buffer) + @property+ def mode(self):+ return self.buffer.mode.replace("b", "")+ def __getattr__(self, name): return getattr(object.__getattribute__(self, "buffer"), name)

Hidden testtest_patch · applied only to grade

diff --git a/testing/test_capture.py b/testing/test_capture.py--- a/testing/test_capture.py+++ b/testing/test_capture.py@@ -1051,6 +1051,9 @@ def test_simple_resume_suspend(self, tmpfile): cap.done() pytest.raises(AttributeError, cap.suspend) + def test_capfd_sys_stdout_mode(self, capfd):+ assert "b" not in sys.stdout.mode+ @contextlib.contextmanager def saved_fd(fd):

1FAIL → PASS

107PASS → PASS

108 / 108green

The agent run

The agent's step-by-step attempt — its reasoning, the tools it called, and the patch it produced.

System promptharness.agent.build_system_prompt

You are an AI coding assistant working inside a code repository that contains a bug. Investigate the code, find the bug, and fix it.

Your working directory is: /testbed
All four tools (read_file, write_file, edit_file, run_bash) already run from that directory. Use plain relative paths; do not prefix shell commands with cd. Fix the bug by editing source files only; do not create or edit test files.

Step 01 tool use

Let me analyze the bug. The issue is about `_pytest.capture.EncodedFile` - its `mode` attribute incorrectly includes `b` (binary), because it's exposing the mode of the underlying stream. The `write()` method of `EncodedFile` only accepts `str` (not `bytes`), but the mode says `rb+` which makes other libraries (like youtube-dl) think they can write bytes to it. Let me look at the relevant code.

read_file{ path: "/testbed/src/_pytest/capture.py" }

tool result · read_file

""" per-test stdout/stderr capturing mechanism. """ from __future__ import absolute_import from __future__ import division from __future__ import print_function import collections import contextlib import io import os import sys from io import UnsupportedOperation from tempfile import TemporaryFile import six import pytest from _pytest.compat import _PY3 from _pytest.compat import CaptureIO patchsysdict = {0: "stdin", 1: "stdout", 2: "stderr"} def pytest_addoption(pars …

Step 02 tool use

Now I understand the issue. The `EncodedFile` class has a `__getattr__` method that delegates attribute access to the underlying buffer. So when someone accesses `.mode` on an `EncodedFile`, it falls through to `__getattr__` and returns the mode of the underlying buffer (which is `rb+`). This makes youtube-dl think it can write bytes to it, but `EncodedFile.write()` only accepts `str`. The fix should be to override the `mode` property in `EncodedFile` to return a mode without `b`. Let me look at the `__getattr__` more carefully: ```python def __getattr__(self, name): return getattr(object.__getattribute__(self, "buffer"), name) ``` So `EncodedFile` proxies all attribute access to the underlying buffer. This means `.mode` returns the buffer's mode (`rb+`), which includes `b`. The fix: add a `mode` property to `EncodedFile` that returns the mode of the underlying buffer but without the `b` character. Let me also check if there's anything else that needs fixing. The `safe_text_dupfile` function also has a potential issue: ```python def safe_text_dupfile(f, mode, default_encoding="UTF8"): encoding = getattr(f, "encoding", None) try: fd = f.fileno() except Exception: if "b" not in getattr(f, "mode", "") and hasattr(f, "encoding"): # we seem to have a text stream, let's just use it return f else: newfd = os.dup(fd) if "b" not in mode: mode += "b" f = os.fdopen(newfd, mode, 0) # no buffering return EncodedFile(f, encoding or default_encoding) ``` The `safe_text_dupfile` creates a file with `mode + "b"` (e.g., `"wb+"`) and wraps it in `EncodedFile`. This is where the `rb+` mode comes from for the underlying buffer. The simplest fix: add a `mode` property to `EncodedFile` that strips `b` from the underlying buffer's mode. Let me implement this.

Now I can see the issue. The `EncodedFile` class uses `__getattr__` to proxy all attribute access to the underlying buffer, including `.mode`. So `EncodedFile.mode` returns `'rb+'` (the mode of the underlying binary stream), even though `EncodedFile.write()` only accepts `str`, not `bytes`. Third-party libraries like youtube-dl check for `'b'` in `mode` to decide whether to write bytes or str, and get confused. The fix is to add a `mode` property to `EncodedFile` that returns the mode without the `'b'`:

edit_file{ path: "/testbed/src/_pytest/capture.py", old_string: " @property\n def name(self):\n \"\"\"Ensure that file.name is a string.\"\"\"\n return repr(self.buffer)\n\n def __getattr__(self, name):\n re…", new_string: " @property\n def name(self):\n \"\"\"Ensure that file.name is a string.\"\"\"\n return repr(self.buffer)\n\n @property\n def mode(self):\n \"…" }

tool result · edit_file

File /testbed/src/_pytest/capture.py edited successfully.

Step 03 tool use

Now let me verify the fix by running a quick test. Let me first check if there are existing tests for EncodedFile.

Now let me verify this works correctly by writing a quick test:

run_bash{ command: "cd /testbed && python -c \"\nfrom _pytest.capture import EncodedFile\nimport io\n\nbuf = io.BytesIO()\nf = EncodedFile(buf, 'utf-8')\nprint('mode:', f.mode)\nprint('has…" }

tool result · run_bash

exitcode: 1 stdout: stderr: Traceback (most recent call last): File "<string>", line 7, in <module> File "/testbed/src/_pytest/capture.py", line 456, in __getattr__ return getattr(object.__getattribute__(self, "buffer"), name) AttributeError: '_io.BytesIO' object has no attribute 'mode'

Step 04 tool use

OK, `BytesIO` doesn't have a `mode` attribute. Let me use a real temporary file instead.

run_bash{ command: "cd /testbed && python -c \"\nfrom _pytest.capture import EncodedFile\nimport tempfile\nimport os\n\ntmpfile = tempfile.TemporaryFile(mode='wb+')\nf = EncodedFile(tmpfi…" }

tool result · run_bash

exitcode: 0 stdout: mode: r+ has b in mode: False write str: OK write bytes: write() argument must be str, not bytes stderr:

Step 05 tool use

The fix works. The mode now returns `r+` instead of `rb+`, and `'b' in f.mode` is `False`. Let me also run the existing test suite for capture to make sure I haven't broken anything.

The fix works. Let me run the existing tests to make sure nothing is broken:

run_bash{ command: "cd /testbed && python -m pytest testing/test_capture.py -x -q 2>&1 | tail -20" }

tool result · run_bash

exitcode: 0 stdout: ..........s........s............s........s...s.......x.................. [ 62%] ..s.....................s.................. [100%] =========================== short test summary info ============================ SKIPPED [1] testing/test_capture.py:894: python2 has no buffer SKIPPED [2] testing/test_capture.py:1118: text output different for bytes on python3 SKIPPED [2] /testbed/testing/test_capture.py:963: could not run 'lsof' …

Step 06 reasoning

All 107 tests pass. Here's a summary of the fix: **Problem:** `EncodedFile` is a wrapper around a binary stream that encodes `str` to `bytes` before writing. Its `write()` method only accepts `str` (rejecting `bytes` on Python 3). However, because `EncodedFile.__getattr__` proxies all attribute access to the underlying binary buffer, accessing `.mode` returned the binary mode (e.g., `'rb+'`). This caused libraries like youtube-dl to see `'b'` in the mode and incorrectly assume they could write `bytes`. **Fix:** Added a `mode` property to `EncodedFile` that returns the underlying buffer's mode with `'b'` stripped out (e.g., `'rb+'` → `'r+'`). This correctly advertises the file as a text-mode stream, matching the behavior of `write()`.

Agent diffcaptured before grading

diff --git a/src/_pytest/capture.py b/src/_pytest/capture.pyindex 25eab7fd..2229f665 100644--- a/src/_pytest/capture.py+++ b/src/_pytest/capture.py@@ -447,6 +447,11 @@ class EncodedFile(object): """Ensure that file.name is a string.""" return repr(self.buffer) + @property+ def mode(self):+ """Ensure that mode does not include 'b' (binary), as write() only accepts str."""+ return self.buffer.mode.replace("b", "")+ def __getattr__(self, name): return getattr(object.__getattribute__(self, "buffer"), name)