fix: respect PYINSTRUMENT_SHOW_CALLBACK when PYINSTRUMENT_PROFILE_DIR is set

[Sanjays2402]

Closes #342

The Django middleware's condition was (show_pyinstrument(request) and url_argument in request.GET) or profile_dir, so as soon as PYINSTRUMENT_PROFILE_DIR was set every request was profiled and PYINSTRUMENT_SHOW_CALLBACK was ignored. The callback now gates both branches, so it can be used to select which requests get written to the profile directory. Regression test fails on main (assert not hasattr(request, "profiler")) and passes with the fix.

[joerick]

Looks good. Thanks.

I really like how the test is written. If you had time to make a few more tests like this for Django and check it was all run in CI that would be great!

[Copilot]

Pull request overview

This PR fixes the Django ProfilerMiddleware gating logic so PYINSTRUMENT_SHOW_CALLBACK is respected even when PYINSTRUMENT_PROFILE_DIR is set, allowing users to selectively record requests to disk.

Changes:

• Update Django middleware condition so PYINSTRUMENT_SHOW_CALLBACK gates both URL-argument profiling and profile-dir recording.
• Add regression tests covering callback behavior when PYINSTRUMENT_PROFILE_DIR is configured.
• Document that PYINSTRUMENT_SHOW_CALLBACK also applies to profile-dir output.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
pyinstrument/middleware.py	Fix conditional so the show callback controls profiling even with PYINSTRUMENT_PROFILE_DIR.
test/test_django_middleware.py	Add regression tests to ensure callback is respected with profile-dir profiling enabled.
docs/guide.md	Clarify documentation about callback behavior when profile-dir output is enabled.

Comments suppressed due to low confidence (1)

test/test_django_middleware.py:48

• Same portability/flake issue here: using a shared hard-coded /tmp/... path can break on non-POSIX platforms and when tests run concurrently. Prefer tmp_path to get an isolated directory for this test.

def test_profile_dir_still_profiles_when_callback_allows():
    from django.test import override_settings

    with override_settings(
        PYINSTRUMENT_PROFILE_DIR="/tmp/pyinstrument-test-profiles",
        PYINSTRUMENT_SHOW_CALLBACK=lambda request: True,
    ):

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[joerick]

+1 to the copilot comment and once the formatter is happy we can get it in.