music_library/backlog/completed/ml-35 - Harden-the-public-asset-endpoint-against-invalid-payloads.md

id, title, status, assignee, created_date, labels, dependencies, references, priority

id	title	status	assignee	created_date	labels	dependencies	references	priority
ML-35	Harden the public asset endpoint against invalid payloads	Done		2026-04-20 08:52			https://github.com/cloud8421/music_library/issues/143	medium

Description

GitHub: created 2026-03-30 · updated 2026-03-30 · closed 2026-03-30

Summary

The public asset endpoint uses bang-style decoding and hard matches during image transformation, so malformed payloads or transform failures can escape as 500s.

Why This Matters

This endpoint is public and cacheable. Invalid user input should degrade to a controlled 400/404 response, not an exception. A corrupted or unsupported asset can also crash request handling.

Evidence

• AssetController.show/2 calls Transform.decode!/1 on a path param.
• cached_get/3 hard-matches {:ok, image_data} from image resize/convert operations.
• The current tests cover missing assets and valid transforms, but not malformed payloads or transform failures.

Affected Files

• lib/music_library_web/controllers/asset_controller.ex
• lib/music_library/assets/transform.ex
• lib/music_library/assets/image.ex
• test/music_library_web/controllers/asset_controller_test.exs

Suggested Fix

Handle invalid payloads and transform failures explicitly: replace bang-style decode with tuple-based validation in the controller boundary; convert failed image processing into a controlled 404/422/500 strategy; add regression tests for malformed payloads and failed conversion/resize paths.

Acceptance Criteria

• Invalid payloads do not raise from the controller.
• Failed image transforms do not crash the request path.
• Tests cover malformed payload and transform failure scenarios.

• #1 Invalid payloads do not raise from the controller.
• #2 Failed image transforms do not crash the request path.
• #3 Tests cover malformed payload and transform failure scenarios.