fix(core): truncate channel state before reloading latest messages

[xsahil03x]

Summary

StreamChannel.reloadChannel was leaving the previously loaded window in place and merging the latest page on top of it via channel.query. After a loadChannelAtMessage(...) jump, that left the around-message window glued to the freshly loaded latest 30 — older messages from before the reload were still in channel.state.messages, and the "scroll to bottom" FAB landed the user on a state that didn't match a fresh open of the channel.

Repro

1. Open a channel scrolled to the bottom (X is one of the visible messages).
2. Tap a quoted reference inside X to jump to an older message Y (the quoted target).
3. loadChannelAtMessage(Y) runs; channel state becomes the around-Y window — X is no longer loaded.
4. Tap the scroll-to-bottom FAB. StreamMessageListView calls reloadChannel() because !_upToDate.
5. Before the fix: state is around-Y ∪ latest 30 (~60 messages). X is unreachable without paginating back; the FAB lands on a state with stale older messages glued underneath the latest.
6. After the fix: state is just the latest 30 — same as a fresh open.

What changed

-/// Reloads the channel with latest message
-Future<void> reloadChannel() => _queryAtMessage();
+/// Reloads the channel with latest messages, replacing the loaded window.
+Future<void> reloadChannel() {
+  channel.state?.truncate();
+  return _queryAtMessage();
+}

The truncate has no effect on persistence — only the in-memory loaded window is cleared. Persistence still hydrates older messages on a fresh session.

The three callers of reloadChannel() semantically want "reset to latest":

Caller	Trigger	Now
MessageListCore.paginate*	pagination failure on a stale window	reload to a fresh latest 30
StreamMessageInput-style send-from-stale-state	sending while not at the latest	reload to a fresh latest 30 before sending
StreamMessageListView.scrollToBottomDefaultTapAction	FAB tap when !_upToDate	reload to a fresh latest 30, then scroll to index 0

Test plan

• flutter test packages/stream_chat_flutter_core/test/stream_channel_test.dart — 25/25 pass (2 new)
• flutter test packages/stream_chat_flutter_core — 191/191 pass
• dart analyze --fatal-infos packages/stream_chat_flutter_core/lib/src/stream_channel.dart — clean
• CI green
• Manual: tap quoted older message → scroll-to-bottom FAB → state is just the latest page

New tests

reloadChannel truncates the existing window before querying the latest messages
reloadChannel queries with no around-anchor (loads the latest page)

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Fixed channel reload so new messages replace the existing message window instead of merging with it, matching a fresh open behavior.

• Tests

  • Added tests verifying previous messages are cleared before fetching and only the latest page is retained after reload.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: b5c367cb-e4bd-4efd-a36b-539b19af3c2c

📥 Commits

Reviewing files that changed from the base of the PR and between 9452ad4 and efa259c.

📒 Files selected for processing (3)

• packages/stream_chat_flutter_core/CHANGELOG.md
• packages/stream_chat_flutter_core/lib/src/stream_channel.dart
• packages/stream_chat_flutter_core/test/stream_channel_test.dart

✅ Files skipped from review due to trivial changes (1)

• packages/stream_chat_flutter_core/CHANGELOG.md

---

📝 Walkthrough

Walkthrough

Calls channel.state?.truncate() before reloading latest messages so reload replaces the existing pagination window; adds widget tests verifying truncation-order, pagination args (no around anchors), and that old messages are dropped; updates CHANGELOG.

Changes

reloadChannel Truncation and Reload

Layer / File(s)	Summary
reloadChannel implementation and tests lib/src/stream_channel.dart, test/stream_channel_test.dart	StreamChannelState.reloadChannel() calls channel.state?.truncate() before _queryAtMessage(). New widget tests setup mutable stateMessages, verify truncate() is called before channel.query() (ordered), assert messagesPagination passed to query() has idAround and createdAtAround null, and confirm final state contains only the latest page.
Changelog documentation CHANGELOG.md	Adds an "Upcoming" → "🐞 Fixed" note stating reloadChannel now replaces the loaded pagination window instead of merging new pages onto the previous window.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested reviewers

• VelikovPetar
• Brazol

Poem

🐰 I nibbled old pages, then made them go,
Truncate the past, let the new messages show.
Fetch fresh pages in tidy array,
No more old crumbs left in the way. 🥕

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix(core): truncate channel state before reloading latest messages' clearly and specifically describes the main change: calling truncate() before reloading. It accurately reflects the core modification in the codebase.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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 fix/reload-channel-truncate

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.33%. Comparing base (508c019) to head (efa259c).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2690   +/-   ##
=======================================
  Coverage   65.33%   65.33%           
=======================================
  Files         423      423           
  Lines       26646    26648    +2     
=======================================
+ Hits        17408    17410    +2     
  Misses       9238     9238           

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