fix(imp): invalidate search cache when mailboxes change

[TDannhauer]

Fix stale IMP search results after delete/move/expunge

Summary

• Invalidate virtual search mailboxes when underlying IMAP folders change (delete, move, expunge).
• Tie search viewport cache IDs to a per-query generation counter so changed() detects stale search results.
• Handle unresolved browser UIDs gracefully when opening a message from outdated search results.

Problem

When messages were deleted from the inbox (moved to Trash or expunged), IMP search could still list them. Clicking such a stale result caused fatal errors in horde.log:

PHP ERROR: Attempt to read property "imp_imap" on null
Error: Call to a member function fetch() on null in Contents.php

Root cause: search results are stored as a virtual mailbox (impsearch…) in the session. That list was cached with a static cache ID ('1') that never changed when underlying folders were modified. Additionally, IMP_Ajax_Application::changed() skipped automatic refresh for search mailboxes unless forceUpdate was set.

Stale browser BUIDs could no longer be resolved to mailbox/UID pairs (fromBuids() returned empty indices), leaving getMailbox() as null and crashing IMP_Contents::_fetchData().

Solution

Search cache invalidation

Add IMP_Search::invalidateMailboxes() to rebuild affected search/virtual-folder lists when folder contents change. Called from:

• IMP_Indices::delete() — after successful delete or move-to-trash
• IMP_Indices::copy() — on move
• IMP_Mailbox::expunge()

Only mailboxes actually modified are tracked; invalidation runs only after successful IMAP operations.

Per-query cache generation

Add a _cacheGen counter on IMP_Search_Query, bumped by invalidateCache(). Search mailbox _getCacheID() now includes this generation alongside sort/hide-deleted preferences, so the viewport cache ID changes when results are invalidated.

Remove the search-only exception in IMP_Ajax_Application::changed(). Re-check changed() in deleteMsgs() after deletion so the viewport refreshes when the search cache ID has moved.

Defensive message load

In IMP_Contents::_fetchData(), throw IMP_Exception when indices resolve to no mailbox (before the IMAP try block). showMessage() already catches this and refreshes the viewport instead of fatalling.

Files changed

• lib/Search/Query.php — cache generation counter, serialization
• lib/Search.php — invalidateMailboxes(), _queryAffected()
• lib/Mailbox.php — dynamic search _getCacheID(), expunge hook
• lib/Indices.php — invalidate on delete/move
• lib/Ajax/Application.php — remove search changed() bypass, re-check after delete
• lib/Contents.php — guard against unresolved BUIDs

Test plan

• Run a quick search in INBOX; delete a result from INBOX (move to Trash). Re-open the search: deleted message must no longer appear.
• Repeat with advanced search scoped to INBOX only and with “all mailboxes”.
• Delete from Trash (expunge). Confirm expunged messages disappear from any active search that included Trash.
• Move messages between folders via drag-and-drop; confirm searches covering source or target folders refresh.
• Click a search result immediately after delete (race/stale BUID): expect “message does not exist” notice, not a PHP fatal in horde.log.
• Confirm no $sortpref warnings in horde.log when opening or refreshing search mailboxes.
• Sort order / hide-deleted toggle on a search mailbox still triggers a viewport refresh.