Fix #5381: disable delete button for last bitstream with tooltip message

[guillermo-escire]

References

• Fixes Cannot delete last Bitstream using new "Edit" menu #5381

Description

Prevents deletion of the last bitstream in the Edit Item form by disabling the delete button when only one file remains and displaying a user-friendly tooltip explaining the restriction.

Instructions for Reviewers

This PR fixes a UX issue where attempting to delete the last bitstream would silently fail due to backend validation, leaving the user without feedback.

List of changes in this PR:

• Added a new totalFiles input to the bitstream component to track the number of files.
• Disabled the delete button when only one bitstream remains.
• Added a tooltip explaining why deletion is not allowed when only one file exists.
• Added a new i18n key (submission.sections.upload.delete.not-allowed) for the tooltip message.
• Ensured the fix applies to both themed and non-themed components.

How to test:

1. Open any Item using the "Edit" menu (submission form).
2. Ensure the Item has at least 2 bitstreams.
3. Delete one bitstream → verify it works normally.
4. When only one bitstream remains:
   • The delete button should be disabled.
   • Hover over the delete icon → a tooltip should explain that at least one file is required.
   • No DELETE request should be triggered (no 422 error in console).
5. Add another bitstream → verify the delete button is enabled again.

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[github-actions]

Hi @guillermo-escire,
Conflicts have been detected against the base branch.
Please resolve these conflicts as soon as you can. Thanks!

[JohnnyMendesC]

Hello @guillermo-escire! Thanks for working on this issue. The visual implementation and the file counting logic work perfectly.

During accessibility testing with a screen reader and keyboard navigation, I noticed two things. One is a requested change for this PR, and the other is a global issue (non-blocker here).

1. Tooltip Accessibility (Requested Change)
Because the native title attribute is used on a standard <span>, screen reader and keyboard-only users cannot access the message explaining why the button is disabled (disabled buttons and standard spans don't receive keyboard focus).

Could we update the wrapper to use an accessible tooltip (like DSpace's ngbTooltip) and add tabindex="0" to it? This ensures all users can read the message.

2. Keyboard bypass on disabled buttons (Non-blocker / Global bug)
While testing, I discovered a global bug in the [dsBtnDisabled] directive itself that allows keyboard bypasses via the Space bar, which triggers the backend error:

@lgeggleston, since this is an issue with the [dsBtnDisabled] directive itself and out of scope for this PR, I understand this could be a non-blocker here. I can open a separate issue/PR to fix the directive globally.

(Note: @guillermo-escire, I left a small inline suggestion to add an early return in the .ts file just as an extra layer of component-level security against this, if you agree).

Great job so far! Let me know if you need help with the tooltip adjustment.

[JohnnyMendesC]

Should we add an early return here as a safeguard?

While testing, I noticed the modal can still be triggered via the Space bar due to a global bug in [dsBtnDisabled]. Adding this early return acts as a great layer of "defense in depth" to ensure this logic is never executed if there's only one file, regardless of UI state.

Suggested change

	public confirmDelete(content) {
	if (this.totalFiles === 1) {
	return;
	}
	this.modalService.open(content).result.then(

[github-actions]

Hi @guillermo-escire,
Conflicts have been detected against the base branch.
Please resolve these conflicts as soon as you can. Thanks!