Handle segmentation when segment alias includes underscore character(s)

[nathanwoulfe]

Ran into this one when working with segments in Engage - segmentation fails in the backoffice (ie split-view editing) when the segment alias includes underscore characters (which it does by default in Engage, and legacy uMarketingSuite installs, and by extension, in any segmented property data).

This is due to how string splits were handled in the various workspace elements when extracting culture and segment from the path:

private _handleVariantFolderPart(index: number, folderPart: string) {
  const variantSplit = folderPart.split('_');
  const culture = variantSplit[0];
  const segment = variantSplit[1];
  this.#workspaceContext?.splitView.setActiveVariant(index, culture, segment);
}

See the issue? Splitting on _ only works correctly when folderPart contains a single _. If the segment includes _, we have incorrect segments:

• en-US_my-segment => en-US, my-segment 💚
• en-US_my_segment => en-US, my 🟥

This PR changes the split handling and relocates some common code from different workspaces into the split view manager. There's a big chunk of duplication in these workspaces, around creating the split and single-view routes, but I've left that untouched (seems like an opportunity to add a UmbContentDetailWorkspaceEditorBaseElement or similar).

Instead of splitting on _, we now find the first index of _ and take the corresponding sub-strings. I've moved the split handling into the UmbVariantId.FromString function to ensure this can be reused easily.

This does potentially change the culture in handleVariantFolderPart, where invariant cultures are now returned as null rather than 'invariant' - this is consistent with how UmbVariantId.FromString has always worked, so I figured it's better to handle invariance consistently. When the resultant UmbVariantId object is stringified, null cultures are set to invariant, so behaviour will not change from previous.

Tangentially related, have also updated the preview app to show segment selector if any segments exist - previously this element only displayed if more than one segment, which meant documents with one segment could not switch to the segment from within the preview app (could preview from the backoffice only).

[Copilot]

Pull Request Overview

This PR fixes a bug in segmentation handling when segment aliases contain underscore characters. The issue occurred in workspace editors where splitting variant folder parts on _ would incorrectly parse segments containing underscores, breaking the split-view editing functionality.

• Refactored variant parsing to use indexOf('_') instead of split('_') to handle underscores in segment names
• Consolidated duplicate code by moving variant handling logic to the split view manager
• Updated preview app to show segment selector when any segments exist (previously required >1 segment)

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
member-workspace-editor.element.ts	Removed duplicate variant handling code, delegated to split view manager
media-workspace-editor.element.ts	Removed duplicate variant handling code, delegated to split view manager
document-workspace-editor.element.ts	Removed duplicate variant handling code, delegated to split view manager
document-blueprint-workspace-editor.element.ts	Removed duplicate variant handling code, delegated to split view manager
workspace-split-view-manager.controller.ts	Added centralized variant parsing methods and delimiter constant
variant-id.class.ts	Fixed parsing logic to handle underscores in segment names correctly
preview-segment.element.ts	Changed condition to show selector when segments exist rather than >1 segments

Comments suppressed due to low confidence (1)

src/Umbraco.Web.UI.Client/src/packages/core/workspace/controllers/workspace-split-view-manager.controller.ts:21

• [nitpick] The constant name VARIANT_DELIMITER should follow TypeScript naming conventions and be in lowercase with underscores, or use a more descriptive name like VARIANT_PART_DELIMITER.

	private readonly VARIANT_DELIMITER = '_&_';

[nielslyngsoe]

Code updates looks good, someone will review and test soon.

[iOvergaard]

• Changed the base of this PR from main to release/16.2 to ensure it gets included.
• New ESLint rules have landed since the inception of this branch, so I updated a few things to allow the linter to pass 🎉
• Prettier wanted to chime in as well and correct a few syntactical things, such as dangling commas

LGTM