ML-169.10: refine implementation plan
This commit is contained in:
Claudio Ortolina
@@ -4,7 +4,7 @@ title: "Fix: Async optimistic UI for index/list delete streams"
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status: To Do
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assignee: []
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created_date: "2026-05-19 11:48"
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updated_date: "2026-05-20 10:12"
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updated_date: "2026-05-22 14:33"
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labels:
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- perf
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- fix
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@@ -102,7 +102,7 @@ Per project conventions, `handle_async` always handles three cases:
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### 1. `IndexActions.handle_delete/2` — shared path (collection + wishlist)
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Replace the synchronous delete with optimistic stream_delete + start_async:
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Replace the synchronous delete with optimistic `stream_delete` + `start_async`:
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```elixir
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def handle_delete(socket, id) do
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@@ -114,7 +114,7 @@ def handle_delete(socket, id) do
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end
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```
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Key: `{:delete_record, id}` as async key ensures uniqueness. The async closure captures `record` — the LiveView task supervisor holds the reference. Do NOT call `load_and_assign_records` — `stream_delete` already removes the item from the stream; a full reload would negate the performance benefit.
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Key: `{:delete_record, id}` as async key ensures uniqueness. Do NOT call `load_and_assign_records` — `stream_delete` already removes the item from the stream; a full reload would negate the performance benefit.
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### 2. `CollectionLive.Index` — handle_async callbacks
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@@ -143,12 +143,14 @@ def handle_async({:delete_record, id}, {:exit, _reason}, socket) do
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end
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```
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Note: Both error cases re-fetch via `Records.get_record!(id)`. For `{:error, reason}`, the record was NOT deleted so re-fetch succeeds. For `{:exit, _reason}`, the task crashed — if the record was deleted before the crash, `get_record!` raises `Ecto.NoResultsError` which crashes the LiveView (acceptable: better than silently showing wrong state).
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Add `alias MusicLibraryWeb.ErrorMessages` to the module.
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### 3. `WishlistLive.Index` — identical handle_async callbacks
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Duplicate the same three `handle_async` clauses from `CollectionLive.Index`. Per project conventions, extraction at 2 callers is premature; extract to `IndexActions` only when a third index page needs it.
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Add `alias MusicLibraryWeb.ErrorMessages` to the module.
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### 4. `ScrobbledTracksLive.Index` — separate async path
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Replace the synchronous delete handler:
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@@ -185,6 +187,8 @@ def handle_async({:delete_track, _uts}, {:exit, _reason}, socket) do
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end
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```
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Add `alias MusicLibraryWeb.ErrorMessages` to the module.
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Key differences from records path:
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- Passes `stream_element` through async tuple so rollback uses the exact same map shape without re-running correlated subqueries (audit Finding 7)
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@@ -192,24 +196,27 @@ Key differences from records path:
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### 5. Tests
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Currently **zero delete test coverage** across all three index test files. Add:
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**Existing coverage to update:**
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Three integration tests exist that test the old synchronous delete path. These must be updated to verify the new async-optimistic behavior (stream_delete + start_async):
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- `collection_live/index_test.exs` — "deletes a record from the listing"
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- `wishlist_live/index_test.exs` — "deletes a record from the listing"
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- `scrobbled_tracks_live/index_test.exs` — "deletes a scrobbled track from the listing"
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**New tests to add:**
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| # | Test | File |
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| --- | ------------------------------------------------------ | --------------------------------------------------- |
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| 1 | Delete record from collection grid (success) | `collection_live/index_test.exs` |
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| 2 | Delete record from wishlist (success) | `wishlist_live/index_test.exs` |
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| 3 | Delete scrobbled track (success) | `scrobbled_tracks_live/index_test.exs` |
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| 4 | handle_async `{:ok, {:ok, ...}}` is no-op | `collection_live/index_test.exs` (unit test) |
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| 5 | handle_async `{:ok, {:error, ...}}` reinserts + toasts | `collection_live/index_test.exs` (unit test) |
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| 6 | handle_async `{:exit, ...}` reinserts + toasts | `collection_live/index_test.exs` (unit test) |
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| 7 | handle_async exit uses generic message (not reason) | `collection_live/index_test.exs` (unit test) |
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| 8 | `data-confirm` attribute present on delete buttons | `collection_live/index_test.exs` (AC #4 regression) |
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| 9 | Show page delete unchanged (still synchronous) | `collection_live/show_test.exs` (AC #5 regression) |
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| 1 | handle_async `{:ok, {:ok, ...}}` is no-op | `collection_live/index_test.exs` (unit test) |
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| 2 | handle_async `{:ok, {:error, ...}}` reinserts + toasts | `collection_live/index_test.exs` (unit test) |
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| 3 | handle_async `{:exit, ...}` reinserts + toasts | `collection_live/index_test.exs` (unit test) |
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| 4 | handle_async exit uses generic message (not reason) | `collection_live/index_test.exs` (unit test) |
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| 5 | `data-confirm` attribute present on delete buttons | `collection_live/index_test.exs` (AC #4 regression) |
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| 6 | Show page delete unchanged (still synchronous) | `collection_live/show_test.exs` (AC #5 regression) |
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Integration tests (tests 1-3): click delete button inside dropdown, verify `refute_has` for the record/track ID, verify record is actually deleted from DB via context module.
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Unit tests (tests 1-4): import the LiveView module, call `handle_async/3` directly with simulated results, assert socket state (stream contents, toast message). This is the preferred approach for testing failure paths since mocking `Repo.delete` is invasive.
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Unit tests (tests 4-7): import the LiveView module, call `handle_async/3` directly with simulated results, assert socket state (stream contents, toast message). This is the preferred approach for testing failure paths since mocking `Repo.delete` is invasive.
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Test 7 specifically asserts that `{:exit, :killed}` produces a generic gettext string, not the raw exit reason — this prevents accidental stacktrace leakage to users.
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Test 4 specifically asserts that `{:exit, :killed}` produces a generic gettext string, not the raw exit reason — this prevents accidental stacktrace leakage to users.
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<!-- SECTION:PLAN:END -->
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