Method _setNodeTypeIfUnset

src/cdk/tree/tree.ts:325–337

* Sets the node type for the tree, if it hasn't been set yet. * * This will be called by the first node that's rendered in order for the tree * to determine what data transformations are required.

(newType: 'flat' | 'nested')

   * to determine what data transformations are required.
   */
  _setNodeTypeIfUnset(newType: 'flat' | 'nested') {
    const currentType = this._nodeType.value;

    if (currentType === null) {
      this._nodeType.next(newType);
    } else if ((typeof ngDevMode === 'undefined' || ngDevMode) && currentType !== newType) {
      console.warn(
        `Tree is using conflicting node types which can cause unexpected behavior. ` +
          `Please use tree nodes of the same type (e.g. only flat or only nested). ` +
          `Current node type: "${currentType}", new node type "${newType}".`,
      );
    }
  }

  /**
   * Switch to the provided data source by resetting the data and unsubscribing from the current