Error: create-react-class could not find the React object.

[neilyio]

I have a very minimal project using figwheel-main and devcards. I'm using npm versions of react and react-dom, as well as the Figwheel {:auto-bundle :webpack} option.

Simply loading my single main.cljs file with a (:require [devcards.core]) results in the following error in the browser:

Error: create-react-class could not find the React object. If you are using script tags, make sure that React is being loaded before create-react-class.

Here's the entire main.cljs:

(ns main.core
  (:require
   [devcards.core]))

Here's my entire deps.edn:

{:deps {org.clojure/clojure       {:mvn/version "RELEASE"}
        org.clojure/clojurescript {:mvn/version "RELEASE"}
        com.bhauman/figwheel-main {:mvn/version "RELEASE"}
        devcards                  {:mvn/version "RELEASE"}
        reagent                   {:mvn/version "RELEASE"
                                   :exclusions [cljsjs/react cljsjs/react-dom]}}

 ;; Run the devcards build with clojure -A:fig --build devcards --repl
 :aliases {:fig {:main-opts ["-m" "figwheel.main"]}}

 :paths   ["src" "cljs-src" "target" "resources"]}

Here's my entire build file, devcards.cljs.edn:

^{:auto-bundle :webpack}
{:main main.core
 :devcards true}

I don't get the error unless I :require devcards.core. This main.cljs, with a regular reagent.dom/render, works fine:

(ns main.core
  (:require [reagent.dom :as rd]))

(defn component []
  [:h1 "hello world!"])

(defn mount []
  (rd/render [component] (.getElementById js/document "main-app-area")))

(defonce init (do (mount) true))