Move/Duplicate: Add early validation for content type and structure constraints (closes #20451)

[iOvergaard]

Summary

Closes #20451

This PR implements early validation for Move and Duplicate operations in the backoffice, providing immediate feedback to users when selecting invalid destinations.

Addressing #20451 - Different Approach

The original issue suggested that invalid destinations should not be selectable at all. We took a lazy validation approach instead, for good reasons:

Why not pre-disable all invalid items?

• Would require fetching allowed children for every visible tree item upfront
• Expensive API calls that scale poorly with large content trees
• Slows down modal opening significantly

Our approach: Validate on selection

• Items are validated when selected (lazy/on-demand)
• Invalid selections show an error message immediately
• After a content type is found invalid, all items of that type become disabled (progressive learning)
• Descendants and self are disabled upfront (cheap to compute from tree data)

This gives users immediate feedback without the performance cost of pre-computing all valid destinations.

Features Added

• Content type validation: Validates that the source item's type is allowed as a child of the destination. Shows error and disables invalid destinations.
• Descendant prevention (Move only): Prevents moving items to their own descendants.
• Same-parent prevention (Move only): Prevents selecting the current parent (no-op).
• Dynamic disabling: Invalid destination types become greyed out after first validation failure.
• Improved modal UX: Item name in headline, error messages in footer with proper styling.

Screenshots

Move Modal - Initial State

Shows item name in headline ("Select where Home should be moved to below"):

Move Modal - Descendants Disabled

All descendants of the source item are automatically disabled (greyed out):

Move Modal - Content Type Error

Error shown when selecting a destination that doesn't allow the source's document type:

Move Modal - Valid Selection

Submit button enabled when a valid destination is selected:

Duplicate Modal - Content Type Error

Same validation for duplicate operations:

Design Notes

Why similar modal code is intentional

The modals for different entity types (documents, media, etc.) have similar but separate implementations. This follows Umbraco's package architecture:

1. Independence - Each package owns its implementations, so changes to the document modal don't risk breaking media or other entity types
2. Extensibility - Entity-specific features can be added without affecting others (e.g., documents have "relate to original" and "include descendants" options that don't apply to media)
3. Avoiding premature abstraction - A shared base class would couple entity types that may diverge in the future

The validation logic (e.g., onTreeSelectionChange) is similar across modals but not identical, and the cost of maintaining a few similar methods is lower than the coupling a shared abstraction would introduce.

Why duplicating to descendants is allowed

Unlike move operations, duplicating a document to one of its descendants is intentionally allowed - it creates a copy without circular reference issues.

Test Plan

• Move document: Right-click → Move to → verify descendants are disabled, invalid types show error, valid selection enables button
• Duplicate document: Right-click → Duplicate to → verify content type validation works (descendants ARE allowed for copy)
• Bulk move/duplicate: Select multiple items → verify "X items" in headline, validation works for all selected items
• Media move: Same validation flow works for media items

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR implements comprehensive early validation for Move and Duplicate operations in the Umbraco CMS backoffice, providing immediate feedback when users select invalid destinations based on content type constraints. The implementation shifts from generic "moveTo" and "duplicateTo" action kinds to custom implementations with validation logic, introduces new modal components with error handling, and adds localization support.

Key Changes:

• Replaces generic action kinds with custom implementations that perform real-time content type validation
• Introduces three new modal components (move-to, duplicate-to variants) with validation callbacks and dynamic tree filtering
• Implements lazy validation that disables invalid destination types after they're selected
• Adds descendant prevention for move operations and current-parent prevention

Reviewed changes

Copilot reviewed 30 out of 30 changed files in this pull request and generated 17 comments.

Show a summary per file

File	Description
move-document.action.ts	New custom implementation for single document move with content type validation and descendant/parent filtering
move-document-bulk.action.ts	New bulk document move action with multi-item validation and error listing
move-media.action.ts	New custom implementation for single media move with content type validation
move-media-bulk.action.ts	New bulk media move action with multi-item validation
duplicate-document.action.ts	Enhanced duplicate action with content type validation via callbacks
duplicate-document-bulk.action.ts	New bulk duplicate action with multi-item validation
move-to-modal.element.ts	New modal component with validation callbacks, dynamic filtering, and error display
duplicate-to-modal.element.ts	New modal component for generic duplicate-to operations with validation support
duplicate-document-modal.element.ts	Enhanced duplicate modal with validation callbacks and error handling
move-to-modal.token.ts	New type definitions for move modal data, including callback interfaces
duplicate-to-modal.token.ts	Enhanced type definitions for duplicate modal with validation callbacks
duplicate-document-modal.token.ts	Enhanced type definitions with validation and submit callbacks
move-to.action.ts	Updated generic move action to use new modal and submit callbacks
duplicate-to.action.ts	Updated generic duplicate action to use callbacks and improved error handling
manifests.ts (documents/media)	Changed from generic "moveTo"/"duplicateTo" kinds to "default" kind with custom API imports
footer-layout.element.ts	Added flexbox alignment to center error messages with buttons
en.ts / da.ts	Updated localization strings to use dynamic item names in modal headlines
commands.md	Added quick verification commands for development workflow