[Tree-Item] expose iconClickHandler

[nsulzberger]

Description

It would be nice if we could listen to the clicks of a user on the expand/collapse icon of a calcite-tree-item.
There is already the iconClickHandler event, but it is not exposed to the users.

Acceptance Criteria

iconClickHandler is exposed

Relevant Info

No response

Which Component

Tree-Item

Example Use Case

We would like to store the state of the tree-items if they are expanded or collapsed, and if the user goes away and returns to the tree we would like to initialize it so the items are expanded where they were expanded before.

Priority impact

p3 - want for upcoming milestone

Esri team

ArcGIS Scene Viewer

[macandcheese]

This makes sense. Maybe we could use expandToggled or other terminology for the public event since the internal iconClick isn't very descriptive and could refer to icons provided via prop, or slotted, etc.

[driskull]

I think the event name here would be calciteTreeItemToggle.

[driskull]

I'm seeing a potential issue with implementing this as is.

• Currently, the click handler for the icon could emit the event, however the arrow right/left keys are handled at the parent tree level.
• Ideally, these keys should emit this event as well since its a user interaction.
• The child expanded state is also being modified when an item is selected in some cases.

  calcite-design-system/packages/calcite-components/src/components/tree/tree.tsx

  Lines 201 to 206 in 02e7124

  	if (
  	shouldUpdateExpand &&
  	["multiple", "none", "single", "single-persist"].includes(this.selectionMode)
  	) {
  	target.expanded = !target.expanded;
  	}

@jcfranco @geospatialem should we have a followup refactoring issue to handle this?

• I think the arrowleft/arrowright events should be moved to the tree-item so that events could be cancelled if necessary and to emit the calciteTreeItemToggle event.
• I'm not sure why the selection event is modifying expanded state.
• I guess we could create an internal method to emit the event when necessary?

[geospatialem]

I'm seeing a potential issue with implementing this as is.

• Currently, the click handler for the icon could emit the event, however the arrow right/left keys are handled at the parent tree level.
• Ideally, these keys should emit this event as well since its a user interaction.
• The child expanded state is also being modified when an item is selected in some cases.

  calcite-design-system/packages/calcite-components/src/components/tree/tree.tsx

  Lines 201 to 206 in 02e7124

  	if (
  	shouldUpdateExpand &&
  	["multiple", "none", "single", "single-persist"].includes(this.selectionMode)
  	) {
  	target.expanded = !target.expanded;
  	}

@jcfranco @geospatialem should we have a followup refactoring issue to handle this?

• I think the arrowleft/arrowright events should be moved to the tree-item so that events could be cancelled if necessary and to emit the calciteTreeItemToggle event.
• I'm not sure why the selection event is modifying expanded state.
• I guess we could create an internal method to emit the event when necessary?

Adding a spike label to determine if the approach above can be pursued or an additional effort should be sought.

[macandcheese]

Related: #8945