Bug: efc-form-controller-lifecycle-and-selection-defects #465

• Work Mode: full-bug

Summary

Four independent defects in EfcFormController: a non-idempotent Cleanup() reachable twice from one
user gesture, a cross-thread WinForms control read inside Task.Run, duplicate "Trash to Delete" rows
accumulating on repeated delete actions, and an inconsistent banner-prefix test across three sites.

Environment

• OS/version: Windows 11 Pro 10.0.26200
• Runtime: .NET Framework 4.8.1 WinForms VSTO add-in
• UI path: QuickFiler/Controllers/EfcFormController.cs
• Data source or fixture: an Email Filer session with folder suggestions populated

Steps to Reproduce

A - double cleanup. Trigger the OK action with the Return key while the OK button Click
subscription is also live; observe the second ActionOkAsync dereference a nulled field.

C - duplicate trash rows. Invoke the delete action twice (via the 'T' keyboard action or the
delete button) and observe two "Trash to Delete" rows in the folder list.

Expected Behavior

• Cleanup() is idempotent, or is guarded so it cannot run twice for one gesture.
• WinForms control properties are read only on the UI thread.
• The trash row appears at most once regardless of how many times delete is invoked.
• A row's banner-prefix classification is identical everywhere it is tested.

Actual Behavior

A - Cleanup() is not idempotent and has no re-entrancy guard (EfcFormController.cs:189-196).
A second invocation dereferences the already-nulled _globals at :191. Two independent paths can
invoke the OK action for a single user gesture: the always-on Return key binding (:365,
new KaKeyAsync("Collection", Keys.Return, (k) => ActionOkAsync())) and the OK button Click
subscription (:391). If both fire, the second ActionOkAsync throws NullReferenceException at
:705 on the nulled _formViewer. EfcHomeController.TryBeginExecuteMoves
(EfcHomeController.ExecuteMoves.cs:48-57) shows the _isExecuting-style guard this path lacks.

B - cross-thread control read (EfcFormController.cs:800-803). RefreshSuggestionsAsync
evaluates _formViewer.SearchText.Text inside the Task.Run lambda. Reading Control.Text off
the UI thread is an illegal cross-thread control access. SearchText_TextChanged (:558) reads the
same property correctly on the UI thread.

C - duplicate trash rows (EfcFormController.cs:742-750). ActionDeleteAsync reads _folderRows,
inserts "Trash to Delete" at index 0, and rebinds. BindFolderRows (:881) then stores the result

• which now contains the trash row - back into _folderRows. A second invocation inserts a second
  trash row. No dedupe guard exists.

D - inconsistent banner-prefix detection. IsValidSelection (:1049) tests
Substring(0, 3) == "===" (three characters); ActionOkAsync (:708) tests StartsWith("====")
(four); BreadcrumbRowBuilder.BannerPrefix (BreadcrumbRowBuilder.cs:19) is "====" (four). A row
beginning with exactly three = is rejected by IsValidSelection but accepted by ActionOkAsync and
classified as a suggestion by the row builder.

Logs / Screenshots

• Attached minimal logs or screenshot
• Code-read evidence recorded above (verified 2026-08-07 against the working tree).

Impact / Severity

• Blocker
• High
• Medium
• Low

Defect A is an unhandled exception on the primary filing gesture. Defect B is an illegal cross-thread
access whose symptom is intermittent and environment-dependent, which makes it hard to attribute.

Source

From: docs/features/potential/2026-08-07-efc-form-controller-lifecycle-and-selection-defects.md