fix: Align types of rootNodeMap during root node tracking

[sdobz]

Description

Issue #39261 describes a mismatch between initial discovery of root nodes and discovery of a new node with a parent.

gatsby/packages/gatsby/src/schema/node-model.js

Line 527 in 4ba9652

ids.push(obj.parent)

  findRootNodeAncestor(obj, predicate = null) {
    let iterations = 0;
    let ids = this._rootNodeMap.get(obj);
    if (!ids) {
      ids = []; // !!! ARRAY TYPE !!!
    }
    if (obj !== null && obj !== void 0 && obj.parent) {
      ids.push(obj.parent); // Error: push does not exist on array
    }

Set(1) { '1afed4c9-65b6-512d-97ab-5c2f6a7aca3b' }

Invesigating _rootNodeMap indeed, it is created as a set

gatsby/packages/gatsby/src/schema/node-model.js

Line 979 in 4ba9652

nodeIds = new Set([nodeId])

    // don't need to track node itself
    if (!isNode) {
      let nodeIds = rootNodeMap.get(data);
      if (!nodeIds) {
        nodeIds = new Set([nodeId]); // !!! SET TYPE !!!
      } else {
        nodeIds.add(nodeId);
      }
      rootNodeMap.set(data, nodeIds);
    }

There appears to be a type disparity between ids as a Set (.add) and ids as an Array (.push)

This code was added in Oct 2022 and includes the type disparity
696a7ba

This is one possible fix. It is unknown why adding parent to markdown frontmatter triggers this issue, there may be further upstream issues

Related Issues

Fixes #39261

[pieh]

Thanks!

[pieh]

Change was released in [email protected]