sphinx-doc/sphinx

sphinx.ext.doctest should ensure that output is patched before importing the target

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#3,891 opened on Jun 25, 2017

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builderextensions:doctesthelp wantedtype:proposal

Description

Problem

  • sphinx.ext.doctest will import the target before making sure that docutils has patched sys.stdout and sys.stderr with _SpoofOut objects. If the target module has already gotten a reference to stdout and stderr and writes to them doctests will fail.

Procedure to reproduce the problem

doctest a function like:

def f(stdout=sys.stdout):
    """
    .. testcode::
        f()
    .. testoutput::
        hello
    """
    stdout.write("hello")

Expected results

a successful doctest, where sys.stdout should be patched before the module under test is imported

Actual results

The output goes to the real sys.stdout, and the doctest fails claiming no output was produced

Contributor guide

Tech stack
python
Domain
documentationtesting
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
basic Pythonunderstanding of doctestfamiliarity with Sphinx extensions
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
65
Research direction
Examine sphinx/ext/doctest.py, specifically the setup function that imports the target module. Ensure that sys.stdout and sys.stderr are replaced with SpoofOut instances before the import occurs. Adjust the order of operations in the doctest extension setup.
sphinx.ext.doctest should ensure that output is patched before importing the target · sphinx-doc/sphinx#3891 | Good First Issue