Pre-download PDFs to file:// URI to avoid stale blob: URIs on iOS

[sentry]

What

Pre-download PDFs to a local file:// URI using expo-file-system before passing to the Pdf component, preventing react-native-pdf from creating blob: URIs internally on iOS.

Changes to app/pdf-viewer.tsx:

• Add download state (cachedUri, downloadError, isDownloading) with a useEffect that calls File.downloadFileAsync on mount, mirroring the existing pattern in pdf-navigation-sheet.tsx
• Show LoadingSpinner while the download is in progress
• Pass the local file:// cachedUri to the Pdf component's source prop
• Pass cachedUri ?? uri to PdfNavigationSheet so it reuses the already-downloaded file instead of downloading redundantly
• Filter stale-blob errors ('Unable to resolve data for blob:') from Sentry.captureException in the onError callback
• Handle download failure by showing the existing error/retry UI

Changes to tests/app/pdf-viewer.test.tsx:

• Update existing tests to await waitFor for the async download to complete before asserting
• Add test: loading spinner displays while download is pending
• Add test: error view displays when download fails

Why

On iOS with Hermes, blob: URIs created by react-native-blob-util (used internally by react-native-pdf) become unresolvable after JS runtime resets. The native RCTBlobManager blob store is cleared on restart, but blob: URI references can persist in TanStack Query cache, navigation state, or background tab mounts via Expo Router. This causes 'Unable to resolve data for blob: UUID' crashes when the app is reopened.

By pre-downloading to a file:// path, react-native-pdf receives a local file and never invokes react-native-blob-util to create a blob: URI, eliminating the stale reference entirely.

Test results

All 28 test suites pass (197 tests), including 2 new tests for the download lifecycle:

Test Suites: 28 passed, 28 total
Tests:       197 passed, 197 total

TypeScript compiles cleanly (tsc --noEmit — no errors).

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Built with Claude Sonnet 4. Prompted with the root cause analysis and proposed solution from the issue description.

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Note

Low Risk
Scoped to PDF viewing and caching; no auth or payment changes, with added tests for download and retry edge cases.

Overview
The PDF viewer now downloads remote PDFs to cache with expo-file-system before mounting react-native-pdf, shows a loading spinner until the local file:// path is ready, and feeds that path into both the main viewer and the navigation sheet (cachedUri ?? uri) so thumbnails do not re-fetch the same remote URL.

Error handling treats download failures like render failures (shared retry UI), cancels in-flight downloads on unmount/retry so late failures do not overwrite a successful retry, and suppresses Sentry for known stale blob: resolution errors while still surfacing other PDF errors.

PdfNavigationSheet skips downloadFileAsync when the URI is already file://, matching the viewer’s cached file. Tests cover the async download lifecycle, retry races, and navigation-sheet download vs local behavior.

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[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

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[greptile-apps]

Greptile Summary

This PR pre-downloads PDFs to a local file:// path using expo-file-system before mounting the react-native-pdf component, eliminating the stale blob: URI crash on iOS Hermes runtimes where the RCTBlobManager store is cleared after JS resets.

• app/pdf-viewer.tsx: Adds a downloadPdf callback with cancelled-flag cancellation stored in a cancelDownloadRef, a loading-spinner state, download-error UI, sharing falls back to a fresh download only when cachedUri is null, and PdfNavigationSheet receives cachedUri ?? uri to avoid redundant network fetches.
• components/pdf-navigation-sheet.tsx: Short-circuits downloadFileAsync when the uri is already file://, preventing the re-download error state described in the previous review thread.
• Tests: All existing tests updated to await waitFor for the async download before asserting, plus new tests covering the loading state, download failure, stale-retry race, and the share-using-cached-URI path.

Confidence Score: 5/5

Safe to merge — change is scoped to PDF loading and does not touch auth, payments, or any shared infrastructure.

All state transitions (download → loading → render, download failure → retry, stale retry cancellation) are correctly guarded by the cancelled-flag pattern. The PdfNavigationSheet re-download regression from the previous review is fixed with the isLocalFile guard. The share handler correctly prefers the already-cached URI. New tests cover every new code path including the deferred-promise race.

No files require special attention.

Important Files Changed

Filename	Overview
app/pdf-viewer.tsx	Core change: pre-download loop with cancellation ref, loading/error states, stale-blob Sentry filter, share using cachedUri. Logic is correct — cancellation, retry, and state transitions all handled properly.
components/pdf-navigation-sheet.tsx	Adds isLocalFile guard to skip downloadFileAsync for file:// URIs and pass them directly to cachedUri — correctly addresses the previous review finding about re-triggering the download with a local source.
tests/app/pdf-viewer.test.tsx	Tests updated to await the async download before asserting, with new coverage for loading spinner, download failure, stale-retry race (deferred promises), and share-using-cached-URI.
tests/components/pdf-navigation-sheet.test.tsx	New test file covering remote-download-then-thumbnail and local-file-direct-use paths — provides full coverage for the isLocalFile guard.

_{Reviews (3): Last reviewed commit: "Use cached PDF for sharing" | Re-trigger Greptile}

[gumclaw]

Fixed the bot review findings in d0e811d: retry downloads now cancel prior attempts, PdfNavigationSheet uses file:// URIs directly instead of re-downloading them, and the PDF viewer tests cover loading, scoped download failures, stale retry races, and local/remote thumbnail download behavior.\n\nVerification:\n- yarn test --runInBand\n- yarn typecheck\n- yarn lint\n- yarn prettier --check app/pdf-viewer.tsx components/pdf-navigation-sheet.tsx tests/app/pdf-viewer.test.tsx tests/components/pdf-navigation-sheet.test.tsx

[gumclaw]

Follow-up fixed the remaining Greptile summary P1 in cf676f1: the share button now uses the already-cached file:// PDF when available instead of re-downloading the original remote URL, with regression coverage that sharing only performs the initial cache download.\n\nVerification after cf676f1:\n- yarn test --runInBand (201 tests passed)\n- yarn typecheck\n- yarn lint\n- yarn prettier --check app/pdf-viewer.tsx tests/app/pdf-viewer.test.tsx\n- GitHub checks: test + Cursor Bugbot passing

[gumclaw]

Assigning @nyomanjyotisa per Gianfranco.

[nyomanjyotisa]

Assigned-to-me.mp4