[Query Builder] Refactor, bug fixing and test coverage improved

[ivanvpetrov]

Description

• Raises Query Builder unit test coverage from 88.7% to ~98.4% (lines).
• Fixes several bugs that were exposed during the refactor, with tests for each.
• Removes dead code.

Fixes

• Keyboard drag:
  • Pressing Space did nothing, because the listener checked for 'Space' while the browser reports ' '.
  • Pressing Space or Enter before choosing a drop location deleted the dragged expression. Both keys now drop only once a drop ghost is shown.
  • ArrowUp/ArrowDown and the Space/Enter key that drops now call preventDefault() (held keys included), so the page/container no longer scrolls.
  • Tab and Shift+Tab are ignored while the drop ghost is shown, so focus stays on it until the condition is dropped (Enter/Space) or the drag is cancelled (Escape). Previously they cancelled the drag and focus was lost.
• Mouse drag + keyboard:
  • While a chip is held with the mouse and its drop ghost is shown, tabbing to another chip's drag indicator let ArrowUp/ArrowDown move the drop ghost without moving the mouse, and Space/Enter drop the mouse-dragged chip there.
  • Focusing another chip's drag indicator during a mouse drag (before a drop ghost appears) started a keyboard drag of that other chip.
  • Added a guard that prevents keyboard drag while a mouse drag is in progress.
• Time fields: selecting a time field without editorOptions threw an error (editorOptions!.dateTimeFormat, now ?.).

Unreachable code removed (all private/protected/@hidden @internal; IgxQueryBuilderTreeComponent is not exported):

• Unused getters (editingInputsContainer, currentGroupButtonsContainer), endGroup(), onKeyDown()
• addRootAndGroupButton @ViewChild, whose template ref no longer exists (setAddButtonFocus keeps its behavior)
• _expandedExpressions, which was never written to
• String handling for _selectedReturnFields, which is always an array; the type is narrowed to string[]
• The unreachable 'wrong key' branch in arrowDrag; the key is typed as 'ArrowUp' | 'ArrowDown'
• The commented-out Tab-blocking code in the drag service, now implemented (see Fixes)

Tests

• New specs for: add-menu flows (add group, add-mode transitions, nested query), focus/blur, return fields, time/dateTime/currency/percent/untyped fields, an entity without fields, return-field chip text, commit()/setAddButtonFocus(), AND/OR switch before the first commit, and resource strings.
• Drag and drop: no-op events, re-targeting, release outside a drop area, focus-out cancel, focus moving to the drop ghost, keyboard input ignored during a mouse drag, default prevented for keyboard-drag keys, and Tab blocked during a keyboard drag.
• Re-enabled the disabled xit drop-ghost spec. Its hard-coded pointer offsets missed the drop target, so it now moves the pointer to the measured "Add condition" button.

Follow-ups / known limitations

• Escape during a mouse drag still only hides the drop ghost; it can't end the drag yet. That needs a cancel API in igxDrag: Drag and Drop: allow cancelling an in-progress drag (Escape key / public API) #17735.
• During a mouse drag with no drop ghost shown yet, Tab to another chip's drag indicator + Enter/Space opens that chip for editing (the chip's own key handler runs before the drag guard). Accepted edge case.

Motivation / Context

Improve Query Builder test coverage.

Type of Change (check all that apply):

• Bug fix
• New functionality
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactoring (no functional changes)
• Documentation
• Demos
• CI/CD
• Tests
• Changelog
• Skills/Agents

Component(s) / Area(s) Affected:

Query Builder (also used by grid advanced filtering)

How Has This Been Tested?

• Unit tests
• Manual testing
• Automated e2e tests

All query-builder specs and the non-grid suite pass. All specs that open grid advanced filtering pass (390). npm run lint:lib reports no errors.

Test Configuration:

• Angular version: 22
• Browser(s): Chrome Headless
• OS: Windows 11

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes (migrations guidelines)
• This PR includes behavioral changes and the feature specification has been updated with them
• Accessibility (ARIA, keyboard navigation, focus management) has been verified

[Copilot]

🟢 Approval recommended

The implementation matches the described fixes and includes comprehensive regression coverage with no unresolved issues found.

0 open findings

🧠 Review effort: Balanced