findDOMNode is deprecated in StrictMode

[barabo]

Ever since I put a custom <Resource> element as a child of a blueprint <Checkbox> element, I've seen errors like this in the console:

index.js:1 Warning: findDOMNode is deprecated in StrictMode.
findDOMNode was passed an instance of Blueprint3.ResizeSensor
which is inside StrictMode. Instead, add a ref directly to the element
you want to reference. Learn more about using refs safely here:
https://fb.me/react-strict-mode-find-node
    in span (created by InnerReference)
    in Blueprint3.ResizeSensor (created by InnerReference)
    in InnerReference (created by Context.Consumer)
    in Reference (created by Blueprint3.Popover)
    in span (created by Blueprint3.Popover)
    in Manager (created by Blueprint3.Popover)
    in Blueprint3.Popover (created by Blueprint3.Tooltip)
    in Blueprint3.Tooltip (at FHIRResource.js:48)
    in Resource (at ListsPanel.js:17)
    in label (created by Control)
    in Control (created by Blueprint3.Checkbox)
    in Blueprint3.Checkbox (at ListsPanel.js:16)
    in td (at ListsPanel.js:15)
    in tr (at ListsPanel.js:14)
    in tbody (at ListsPanel.js:34)
    in table (at ListsPanel.js:33)
    in ListSelector (at ListsPanel.js:135)
    in div (at ListsPanel.js:132)
    in ListsPanel (at App.js:49)
    in div (at App.js:48)
    in div (at App.js:47)
    in div (at App.js:32)
    in App (at src/index.js:9)
    in StrictMode (at src/index.js:8)

The offending lines are as follows in ListPanel.js:

     1  import { drain, getRefsFrom, filterLists } from 'api';
     2  import React from 'react';
     3  import 'components/ListsPanel.css'
     4  import { Checkbox } from "@blueprintjs/core";
     5  import { Resource } from 'components/FHIRResource';
     6  
     7  const debug = false;  // XXX
     8  
     9  // A FHIR Resource in a table row.
    10  function ResourceRow(props) {
    11    const resource = props.resource;
    12    const key = `${resource.resourceType}/${resource.id}`;
    13    return (
    14      <tr key={key}>
    15        <td>
    16          <Checkbox>
    17            <Resource
    18              display={resource.name}
    19              resource={resource}
    20            />
    21          </Checkbox>
    22        </td>
    23      </tr>