A bare <ace> tag raises "foreach() argument must be of type array|object, false given" on every render

Problem/Motivation

An <ace> tag without attributes raises a warning every time the text is rendered:

Warning: foreach() argument must be of type array|object, false given in Drupal\ace_editor\Plugin\Filter\AceFilter->process() (line 141 of src/Plugin/Filter/AceFilter.php).
Drupal\ace_editor\Plugin\Filter\AceFilter->process() (Line: 122)
Drupal\filter\Element\ProcessedText::preRenderText()

tagAttributes() returns FALSE when the tag carries no attributes, and process() iterates over that return value without a guard.

A tag with no attributes is the documented basic usage - docs/index.md and docs/1-users/3-filter.md both introduce the filter as <ace> ... </ace> - so the warning appears on the simplest case the module offers. The snippet itself still renders; the attribute loop is skipped, which is correct when there are no attributes, so the effect is a warning on every render rather than broken output.

The existing unit test testNoAttributesReturnsFalse() asserted the FALSE return, so the contract was locked in by a test while no caller could handle it.

Steps to reproduce

1. Enable the Ace Filter on a text format.
2. Put a tag with no attributes in a node body: <ace>const value = 1;</ace>
3. View the node with error reporting set to show warnings.

Reproduced on Drupal 11.4.5, PHP 8.4. tagAttributes('ace', '<ace>code</ace>') returns false, and so does '<ace >code</ace>'.

Proposed resolution

Return an empty array from tagAttributes() when the tag carries no attributes. An accessor with nothing to report returns an empty set, iterating it is a no-op, and an existing if (!$attributes) check keeps behaving the same because an empty array is falsy.

The unit test is updated to assert the empty array, and a kernel test covers processing a bare tag, an attributed tag, both together, and text with no tag, asserting that nothing is raised in each case.

Screenshots

The same node, carrying a tag with no attributes, before and after the fix.

Remaining tasks

• ✅ File an issue
• ✅ Addition/Change/Update/Fix
• ✅ Testing to ensure no regression
• ✅ Automated unit/functional testing coverage
• ➖ Developer Documentation support
• ➖ User Guide Documentation support
• ➖ UX/UI designer responsibilities
• ➖ Accessibility and Readability
• ❌ Reviewed by a human
• ❌ Code review by maintainers
• ❌ Full testing and approval
• ❌ Credit contributors
• ❌ Review with the product owner
• ❌ Update Release Notes
• ❌ Release

User interface changes

• N/A

API changes

• AceFilter::tagAttributes() returns an empty array instead of FALSE when a tag carries no attributes.

Data model changes

• N/A

Release notes snippet

• Fixed a warning raised on every render of an <ace> tag that carries no attributes.