Implicit App Discovery is Brittle (Use CUSTOM_APPS Instead)

[wesleyboar]

Note

Generated by AI. Edited by @wesleyboar.

Summary

taccsite_cms/settings.py currently scans taccsite_custom subdirectories with a helper like get_subdirs_as_module_names and appends them to INSTALLED_APPS at runtime. This implicit app discovery is brittle and causes surprising behavior.

Files / Locations

• taccsite_cms/settings.py — discovery + append to INSTALLED_APPS

Problems / Impact

• Non-deterministic app ordering can break template resolution, signal/middleware ordering, and migrations.
• Makes it hard to reason about which apps are enabled; accidental subdirs can be loaded as apps.
• Hard to test and CI-validate because the environment can produce different lists depending on filesystem order/globs.
• Migration and management commands can behave differently between environments.

Proposed (Backward-Compatible) Approach

1. Use existing optional setting CUSTOM_APPS (list of module names). Use it instead of scanning.
2. If keeping current scanning behavior as a fallback for backward compatibility:
   • Sort discovered module names deterministically (e.g. alphabetically) before appending.
   • Emit a deprecation warning (e.g. logging.warn) when discovery is used.
3. Add a validation step on startup (or a management command) that prints the final INSTALLED_APPS order and flags duplicates or likely issues.
4. Document the new setting in taccsite_custom/README.md and docs/ with migration steps.

Minimal Migration Plan / Tests

• Tests: unit test that discovery returns a stable, sorted list; integration test that explicitly provided TACCSITE_CUSTOM_APPS results in expected INSTALLED_APPS.

Warning

Teams who want determinism can use setting CUSTOM_APPS, but use of that setting can not be an "opt-in" signal, because all custom Core-CMS instances already use CUSTOM_APPS (for other custom apps).

Client Apps

These apps rely on TACC/Core-CMS:

• https://github.com/TACC/tup-ui/tree/v1.1.17/apps/tup-cms/src
• https://github.com/TACC/APCD-CMS/tree/v1.3.1/apcd_cms/src
• https://github.com/TACC/Texascale-CMS/tree/v1.3.0/cms/src