fix(#304): stop deduplicate() from discarding favorites, read state, and podcast progress

[cassio-rossi]

Summary

Fixes #304 — favorites (and other per-device user state) being silently lost, most visibly when updating the app, but not limited to that trigger.

Root cause: FeedDB.deduplicate()/PodcastDB.deduplicate() resolve duplicate postId groups — created whenever a local feed/podcast refresh races an in-flight iCloud import (multi-device sync, or a cold launch right after an app update) — purely by recency (modifiedAt). A freshly-synced, blank duplicate (favorite: false, modifiedAt: Date() at construction) could out-rank an older row that actually carried the user's favorite, silently deleting it. PodcastDB additionally grouped by pubDate instead of postId, so two unrelated episodes sharing a timestamp could be merged incorrectly.

Fix, in three passes (see individual commits):

1. Group PodcastDB duplicates by postId (matching FeedDB); prefer a favorited/read copy over a merely-newer one.
2. Extend the same protection to podcast playback progress (current), which has no read equivalent but is exposed to the identical race.
3. Replace the boolean OR-merge with per-field authority timestamps (favoriteModifiedAt, readModifiedAt, progressModifiedAt), because OR-merging can only turn a flag on — it was silently resurrecting a legitimate cross-device un-favorite or "mark unread." deduplicate() now picks the content survivor by plain modifiedAt recency, then merges favorite/read/current independently by whichever duplicate has the latest own timestamp for that specific field — so a spurious sync row (.distantPast) never outranks a real action, and a genuine newer un-favorite/mark-unread/rewind correctly overrides an older one.

Confirmed via the guide-swiftdata skill that @Model silently ignores didSet/willSet, so each field-mutation is centralized instead in explicit model methods (toggleFavorite(), toggleRead(), markAsRead(), updateProgress(_:)) that stamp the field and its timestamp together, replacing a duplicated 3-line pattern at every call site.

Test plan

• xcodebuild build succeeds (iPhone 17 Pro Max simulator — iPhone 17 Pro is not installed on this machine)
• xcodebuild test -testPlan MacMagazine — 108 tests, 0 failures
• swiftlint lint --strict — 0 violations across all changed files
• New regression coverage: favorite-over-recency, explicit cross-device unfavorite, read-only merge, field independence, podcast progress merge (spurious duplicate, deliberate rewind, favorite+progress independence), toggleFavorite/toggleRead/markAsRead/updateProgress timestamp isolation

Co-Authored-By: Claude noreply@anthropic.com

[cassio-rossi]

Automated code review (Claude Code)

🔴 Correctness

1. NewsLibrary/Sources/NewsLibrary/Views/NewsView.swift:233
The primary article-read path (.task on the news detail sheet) sets read/modifiedAt directly instead of calling the new markAsRead(), so readModifiedAt never advances.

User opens an article on Device A (read = true but readModifiedAt stays .distantPast). A stale synced duplicate with any readModifiedAt later arrives from iCloud/refresh and out-ranks it in FeedDB.deduplicate()'s per-field merge (FeedDB.swift:131), silently reverting the article to unread — the exact class of bug this PR claims to fix, reintroduced via the main reading flow.

2. MacMagazine/Features/News/DeepLinkNewsDetailView.swift:60
The favorite toggle in the deep-link article detail view mutates favorite/modifiedAt directly instead of calling toggleFavorite(), leaving favoriteModifiedAt stale.

User taps a push-notification deep link and favorites the article here; favoriteModifiedAt never updates from .distantPast. If a duplicate record exists with any later favoriteModifiedAt, deduplicate() (FeedDB.swift:127) will pick the other record's favorite value, silently discarding the favorite set from this screen.

3. MacMagazine/Features/News/DeepLinkNewsDetailView.swift:47
.onAppear in the deep-link detail view sets read/modifiedAt directly instead of calling markAsRead() — same bypass as the main NewsView flow.

Opening an article via push notification marks it read without stamping readModifiedAt; a later deduplicate() pass can revert read to false if a duplicate carries a newer readModifiedAt, silently losing read state for anything opened via deep link.

4. FeedLibrary/Sources/FeedLibrary/Database/FeedDB.swift:37
The designated initializer has a parameter typo ead: Bool = false (missing leading r); the body's self.read = read resolves read to the implicit self.read (self-assignment), so the ead: argument is silently discarded and read can never be set to true through the initializer.

Verified by compiling a minimal @Model reproduction: Foo(ead: true) followed by reading f.read yields false with zero compiler diagnostic once @Model is applied. Correctly-labeled calls (read:) won't compile at all; the misleadingly-correct ead: label silently no-ops — a latent trap sitting directly inside the exact initializer this PR extended.

5. MacMagazineLibrary/Sources/MacMagazineLibrary/ModelProtocols.swift:21
ModelPrioritizable.latest() uses group.max(by:), whose last-wins tie-break makes the merge non-deterministic when two duplicates share the exact same authority timestamp (e.g. both still at .distantPast).

Two duplicate PodcastDB rows both have progressModifiedAt == .distantPast but different current values. latest()'s tie-break depends on Dictionary(grouping:).values iteration order, which is unspecified — the merge outcome can differ between app launches/devices for the same data, contradicting the PR's goal of deterministic, authority-based resolution.

🟡 Duplication

6. FeedLibrary/Sources/FeedLibrary/Database/PodcastDB.swift:88
FeedDB.deduplicate() and PodcastDB.deduplicate() are now near-identical ~15-line bodies (fetch → group by postId → max-modifiedAt survivor → two latest() field merges → delete non-survivors → save), duplicated instead of shared, even though the comparison primitive (ModelPrioritizable.latest) already lives in shared MacMagazineLibrary.

A future fix to the merge/survivor logic must be applied and tested twice, in two files, with no compiler tie between them.

⚪ Style

7. FeedLibrary/Sources/FeedLibrary/Database/FeedDB.swift:85
New public API (toggleFavorite(), toggleRead(), markAsRead() on FeedDB; toggleFavorite(), updateProgress() on PodcastDB; ModelPrioritizable.latest()) has no /// DocC comments, per CLAUDE.md's explicit rule.

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🤖 Generated with Claude Code