fix(django): handle request.user in async middleware context

[webjunkie]

Summary

Fixes SynchronousOnlyOperation when accessing request.user in ASGI deployments with Django + Uvicorn.

Note: This PR is stacked on #350 (process_exception fix). Both will be released together as v6.7.12.

Problem

Django's request.user is a SimpleLazyObject that defers database access until the attribute is touched. In async context, accessing it triggers blocking DB operations, raising SynchronousOnlyOperation.

The middleware was calling synchronous extract_tags() in __acall__(), which accessed request.user directly:

async def __acall__(self, request):
    for k, v in self.extract_tags(request).items():  # ← Calls sync method
        contexts.tag(k, v)

This worked in sync (WSGI) but failed in async (ASGI).

Root Cause Timeline

• v6.7.5 (PR feat(err): add __acall__ to django middleware #328): Introduced async support with this bug, but ASGI was too broken to discover it
• v6.7.10 (PR fix(django): make middleware truly hybrid-compatible with sync and async Django stacks #348): Fixed ASGI functionality → users could actually run ASGI → bug became visible
• User reported in [Django + ASGI] middleware breaks when getting user from request #355: Running Django 5.2.7 + Uvicorn 0.38.0

Solution

Add async versions of extraction methods following Django's naming convention:

• aextract_tags() - async version of extract_tags()
• aextract_request_user() - uses await request.auser() instead of request.user
• Update __acall__() to call async versions

Follows Django's pattern for async methods (auser(), asave(), aget(), etc.).

Changes

• Add aextract_tags() method
• Add aextract_request_user() method using await request.auser()
• Update __acall__() to use await self.aextract_tags(request)
• Add comprehensive Django 5 integration test suite with real ASGI application
• Add CI job for Django 5 integration tests

Django 5 Integration Tests

New test_project_django5/ with real Django 5.2.7 ASGI app:

• Tests async user access with request.auser()
• Tests exception capture via process_exception()
• Tests authenticated user with SimpleLazyObject (triggers bug in v6.7.11)
• Uses httpx AsyncClient for in-process testing
• Pinned dependencies to prevent drift
• Runs in separate CI job on Python 3.12

Async Safety Notes

The following operations in aextract_tags() are async-safe:

• ✅ request.auser() - now uses async version
• ✅ request.headers.get() - dict access
• ✅ request.build_absolute_uri() - string building
• ✅ request.method, request.path - attribute access

Note on callbacks: If you configure POSTHOG_MW_EXTRA_TAGS or POSTHOG_MW_TAG_MAP, ensure these functions don't perform blocking I/O (database queries, file operations, etc.) as they're called in async context. Keep them lightweight or they may raise SynchronousOnlyOperation.

Test Results

• All 19 unit tests pass (Python 3.9-3.13)
• All 7 Django 5 integration tests pass

User Workaround Validation

User's workaround in #355 used the same approach (async methods with request.auser()), validating this solution.

Fixes #355

[greptile-apps]

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