Introduce mixed_descendants selection strategy

Author: HDinger

app/components/primer/alpha/tree_view/sub_tree_node.rb

@@ -8,10 +8,11 @@ class TreeView
       # This component is part of the <%= link_to_component(Primer::Alpha::TreeView) %> component and should
       # not be used directly.
       class SubTreeNode < Primer::Component
-        DEFAULT_SELECT_STRATEGY = :descendants
+        DEFAULT_SELECT_STRATEGY = :mixed_descendants
         SELECT_STRATEGIES = [
           :self,
-          DEFAULT_SELECT_STRATEGY
+          DEFAULT_SELECT_STRATEGY,
+          :descendants
         ]
 
         # @!parse
@@ -59,7 +60,7 @@ class SubTreeNode < Primer::Component
               visual: IconPair.new(
                 **system_arguments,
                 expanded: @sub_tree.expanded?,
-              )
+                )
             )
           }
         }
@@ -108,10 +109,19 @@ class SubTreeNode < Primer::Component
         # @param label [String] The node's label, i.e. it's textual content.
         # @param path [Array<String>] The node's "path," i.e. this node's label and the labels of all its ancestors. This node should be reachable by traversing the tree following this path.
         # @param node_variant [Symbol] The variant to use for this node. <%= one_of(Primer::Alpha::TreeView::NODE_VARIANT_OPTIONS) %>
+        # @param sub_tree_component_klass [Class] The class to use for the sub-tree instead of the default <%= link_to_component(Primer::Alpha::TreeView::SubTree) %>
         # @param expanded [Boolean] Whether or not this sub-tree should be rendered expanded.
         # @param select_strategy [Symbol] What should happen when this sub-tree node is checked. <%= one_of(Primer::Alpha::TreeView::SubTreeNode::SELECT_STRATEGIES) %>
         # @param system_arguments [Hash] The arguments accepted by <%= link_to_component(Primer::Alpha::TreeView::Node) %>.
-        def initialize(label:, path:, node_variant:, expanded: false, select_strategy: DEFAULT_SELECT_STRATEGY, **system_arguments)
+        def initialize(
+          label:,
+          path:,
+          node_variant:,
+          sub_tree_component_klass: SubTree,
+          expanded: false,
+          select_strategy: DEFAULT_SELECT_STRATEGY,
+          **system_arguments
+        )
           @label = label
           @system_arguments = system_arguments
           @select_strategy = fetch_or_fallback(SELECT_STRATEGIES, select_strategy, DEFAULT_SELECT_STRATEGY)
@@ -123,16 +133,16 @@ def initialize(label:, path:, node_variant:, expanded: false, select_strategy: D
 
           @system_arguments[:data] = merge_data(
             @system_arguments, {
-              data: {
-                target: "tree-view-sub-tree-node.node",
-                "node-type": "sub-tree"
-              }
+            data: {
+              target: "tree-view-sub-tree-node.node",
+              "node-type": "sub-tree"
             }
+          }
           )
 
           sub_tree_arguments = @system_arguments.delete(:sub_tree_arguments) || {}
 
-          @sub_tree = SubTree.new(
+          @sub_tree = sub_tree_component_klass.new(
             expanded: expanded,
             path: path,
             node_variant: node_variant,

app/components/primer/alpha/tree_view/tree_view_sub_tree_node_element.ts

@@ -7,6 +7,8 @@ import type {TreeViewNodeInfo} from '../../shared_events'
 
 type LoadingState = 'loading' | 'error' | 'success'
 
+export type SelectStrategy = 'self' | 'descendants' | 'mixed_descendants'
+
 @controller
 export class TreeViewSubTreeNodeElement extends HTMLElement {
   @target node: HTMLElement
@@ -70,7 +72,7 @@ export class TreeViewSubTreeNodeElement extends HTMLElement {
     )
 
     const checkedMutationObserver = new MutationObserver(() => {
-      if (this.selectStrategy !== 'descendants') return
+      if (this.selectStrategy !== 'mixed_descendants') return
 
       let checkType = 'unknown'
 
@@ -127,8 +129,8 @@ export class TreeViewSubTreeNodeElement extends HTMLElement {
     this.#update()
   }
 
-  get selectStrategy(): string {
-    return this.node.getAttribute('data-select-strategy') || 'descendants'
+  get selectStrategy(): SelectStrategy {
+    return (this.node.getAttribute('data-select-strategy') || 'descendants') as SelectStrategy
   }
 
   disconnectedCallback() {
@@ -375,7 +377,7 @@ export class TreeViewSubTreeNodeElement extends HTMLElement {
     const rootInfo = this.treeView?.infoFromNode(this.node, newCheckValue)
     if (rootInfo) nodeInfos.push(rootInfo)
 
-    if (this.selectStrategy === 'descendants') {
+    if (this.selectStrategy === 'descendants' || this.selectStrategy === 'mixed_descendants') {
       for (const node of this.eachDescendantNode()) {
         const info = this.treeView?.infoFromNode(node, newCheckValue)
         if (info) nodeInfos.push(info)

previews/primer/alpha/tree_view_preview.rb

@@ -10,7 +10,7 @@ class TreeViewPreview < ViewComponent::Preview
       # @param expanded [Boolean] toggle
       # @param disabled [Boolean] toggle
       # @param select_variant [Symbol] select [multiple, none]
-      # @param select_strategy [Symbol] select [self, descendants]
+      # @param select_strategy [Symbol] select [self, descendants, mixed_descendants]
       def default(
         expanded: false,
         disabled: false,
@@ -29,7 +29,7 @@ def default(
       #
       # @param expanded [Boolean] toggle
       # @param select_variant [Symbol] select [multiple, none]
-      # @param select_strategy [Symbol] select [self, descendants]
+      # @param select_strategy [Symbol] select [self, descendants, mixed_descendants]
       def playground(
         expanded: false,
         select_variant: Primer::Alpha::TreeView::Node::DEFAULT_SELECT_VARIANT,