Respect an explicit autodiscover list under Django

[wbarnha]

Note: Before submitting this pull request, please review our contributing guidelines.

Description

Fixes #500.

App.discover() unconditionally unioned every fixup's autodiscover_modules() into the set of modules to scan:

for fixup in self.fixups:
    modules |= set(fixup.autodiscover_modules())

The Django fixup's autodiscover_modules() returns all of INSTALLED_APPS. So an app that set an explicit list — e.g. autodiscover=['myproj.agents'] — still had every installed Django app scanned, importing unrelated migrations/admin modules and frequently failing.

This contradicts the Django fixup's own documented behavior:

If faust.App(autodiscovery=True), the Django fixup will automatically autodiscover agents/tasks/web views … found in installed Django apps.

i.e. the INSTALLED_APPS scan is meant for the blanket autodiscover=True mode, not for an explicit list.

Fix

Only pull in fixup-provided modules when conf.autodiscover is True. When the user passes an explicit list (or a callable), honor it as-is. Django itself is still set up independently via Fixup.on_worker_init() (which calls django.setup()), so this does not affect Django initialization — only which modules get scanned for @app.agent/task/view decorators.

Tests

• Updated test_discover (explicit list): asserts the fixup's modules (d, e) are not imported and fixup.autodiscover_modules is not called.
• Added test_discover__true_includes_fixup_modules: with autodiscover=True, the fixup modules are scanned.
• Verified the updated test catches the bug: reverting the fix makes d/e get imported for the explicit-list case.
• flake8 / black --check / isort --check-only clean.

🤖 Generated with Claude Code

---

Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.15%. Comparing base (3073eb9) to head (8192c98).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #697   +/-   ##
=======================================
  Coverage   94.14%   94.15%           
=======================================
  Files         104      104           
  Lines       11136    11137    +1     
  Branches     1201     1202    +1     
=======================================
+ Hits        10484    10486    +2     
+ Misses        551      550    -1     
  Partials      101      101           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.