music_library/backlog/completed/ml-33 - Align-Last.fm-callback-errors-with-app-conventions.md

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

id	title	status	assignee	created_date	labels	dependencies	references	priority
ML-33	Align Last.fm callback errors with app conventions	Done		2026-04-20 08:52			https://github.com/cloud8421/music_library/issues/145	low

Description

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

Summary

The Last.fm OAuth callback bypasses the project's standard user-facing error handling and interpolates raw failure reasons directly into the flash message.

Why This Matters

This is inconsistent with the documented convention for user-facing errors and increases the chance of exposing low-quality or overly-technical error text to users.

Evidence

• MusicLibraryWeb.LastFmController.callback/2 uses put_toast(:error, "Failed to connect your Last.fm account: #{reason}").
• Project conventions say user-facing error reasons should go through ErrorMessages.friendly_message/1 instead of raw inspection/interpolation.
• The current test only checks the flash prefix, so the inconsistency is not exercised.

Affected Files

• lib/music_library_web/controllers/last_fm_controller.ex
• docs/project-conventions.md
• test/music_library_web/controllers/last_fm_controller_test.exs

Suggested Fix

Align the controller with the established convention: keep the contextual prefix, translate the reason through ErrorMessages.friendly_message/1, ensure the resulting string remains wrapped appropriately for localization/user display.

Acceptance Criteria

• The Last.fm callback uses the same user-facing error formatting approach as the rest of the app.
• Tests assert the controller does not expose raw backend error terms in the flash.

• #1 The Last.fm callback uses the same user-facing error formatting approach as the rest of the app.
• #2 Tests assert the controller does not expose raw backend error terms in the flash.