ADFA-4331: Decode opened plugin tabs off the main thread

[fryanpan]

Jira Ticket: https://appdevforall.atlassian.net/browse/ADFA-4331
Sentry Issue: https://appdevforall-inc-9p.sentry.io/issues/APPDEVFORALL-1J

Question

Looks like this file is part of AndroidIDE -- do we make changes here or upstream?

Reproduction Details

A main-thread / ANR-risk performance issue (not a crash). EditorHandlerActivity.restoreOpenedPluginTabs() read the cached-tabs JSON from SharedPreferences and ran Gson().fromJson(...) synchronously on the main thread during startup, stalling the UI.

Stack Trace

No exception (profiling issue). Suspect function:

Gson.fromJson(JsonReader, TypeToken): Object   — on the main thread (warm start)

(issue type: profile_json_decode_main_thread · device.class: low)

User Steps

User steps leading up to crash, based on Sentry breadcrumbs:

• App warm-start with previously-open plugin tabs to restore; the tab-state JSON is decoded on the main thread during onStart, blocking the first frames. (Profiling aggregate; tagged to the startup transaction.)

Was able to reproduce in a unit test?

Yes.
RestorePluginTabsThreadTest (:app, Robolectric) pins Dispatchers.Main, invokes the real private restoreOpenedPluginTabs(), and captures the thread on which its pref write executes (via the EventBus PreferenceChangeEvent). Baseline: write thread == main (FAIL); branch: write thread == DefaultDispatcher-worker (off main). Mutation-sensitive: flipping the prod file flips red/green.

What Was Fixed

Move the pref read + Gson decode + clearing write into withContext(Dispatchers.IO/Default) inside lifecycleScope.launch; UI updates stay on Main.

Testing

:app:testV8DebugUnitTest --tests …RestorePluginTabsThreadTest → green (red on baseline). Local CodeRabbit review: no findings. Reviewer notes (local): remove the leftover println("PROBE: …") debug line in the test; the restore now races the sibling onStart reopen-files coroutine (serialized on Main, theoretical only).

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Fixes APPDEVFORALL-1J

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 461c0821-a65d-4d9d-8130-bacc634b93d2

📥 Commits

Reviewing files that changed from the base of the PR and between 0852a5e and 99467d1.

📒 Files selected for processing (2)

• app/src/main/java/com/itsaky/androidide/activities/editor/EditorHandlerActivity.kt
• app/src/test/java/com/itsaky/androidide/activities/editor/RestorePluginTabsThreadTest.kt

📝 Walkthrough

Walkthrough

restoreOpenedPluginTabs() is refactored from a synchronous implementation to a coroutine-based one that reads SharedPreferences on Dispatchers.IO and parses JSON on Dispatchers.Default. A new Robolectric regression test (ADFA-4331) verifies that the preference-clearing write occurs off the main thread using an EventBus subscriber and CountDownLatch.

Changes

Async plugin tab restore with threading regression test

Layer / File(s)

Summary

Async restore implementation and threading regression test app/src/main/java/com/itsaky/androidide/activities/editor/EditorHandlerActivity.kt, app/src/test/java/com/itsaky/androidide/activities/editor/RestorePluginTabsThreadTest.kt

restoreOpenedPluginTabs is rewritten to launch a coroutine reading PREF_KEY_OPEN_PLUGIN_TABS on Dispatchers.IO, parsing JSON on Dispatchers.Default, and clearing the preference key asynchronously. The regression test seeds preferences, bypasses UI selection via reflection, captures the write-thread name through an EventBus PreferenceChangeEvent subscriber with a CountDownLatch, pumps the test scheduler, and asserts the write occurred off the main thread.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• appdevforall/CodeOnTheGo#853: Originally introduced EditorHandlerActivity.restoreOpenedPluginTabs() and the PREF_KEY_OPEN_PLUGIN_TABS SharedPreferences persistence/restore logic that this PR refactors to run asynchronously.

Suggested reviewers

• dara-abijo-adfa
• jomen-adfa

Poem

🐇 Hoppity-hop, off the main thread I leap,
SharedPrefs and JSON no longer make UI weep.
A latch and a bus catch the write in the night,
Coroutines carry the tabs with delight.
The test sniffs the thread — background, hooray!
This bunny approves of the async display! 🎉

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: moving the JSON decoding of plugin tabs off the main thread to improve performance during startup.
Description check	✅ Passed	The description comprehensively relates to the changeset, detailing the performance issue, reproduction steps, testing approach, and the specific fix applied to move blocking operations off the main thread.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ADFA-4331-restoreplugintabs-json-main-thread

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[hal-eisen-adfa]

Please be careful about possible collisions with PR #1426