Add warning if multiple versions are running (addresses #1470)

packages/jest-emotion/src/index.js

@@ -1,4 +1,5 @@
 // @flow
+import { registerEmotionModule } from '@emotion/utils'
 import * as css from 'css'
 import { replaceClassNames } from './replace-class-names'
 import {
@@ -14,6 +15,12 @@ import {
 
 export { matchers } from './matchers'
 
+registerEmotionModule(require('../package.json').name, 'not it')
+registerEmotionModule(
+  require('../package.json').name,
+  require('../package.json').version
+)
+
 function getNodes(node, nodes = []) {
   if (Array.isArray(node)) {
     for (let child of node) {

packages/utils/src/index.js

@@ -1,7 +1,35 @@
 // @flow
 import type { RegisteredCache, EmotionCache, SerializedStyles } from './types'
 
-let isBrowser = typeof document !== 'undefined'
+const isBrowser = typeof document !== 'undefined'
+
+const getGlobalVersions = (context: any) => {
+  const globalVersionsKey = '__EMOTION_VERSIONS__'
+  if (!context[globalVersionsKey]) {
+    context[globalVersionsKey] = {}
+  }
+  return context[globalVersionsKey]
+}
+
+type ModuleVersions = { [key: string]: string }
+
+const versions: ModuleVersions = getGlobalVersions(isBrowser ? window : global)
+
+export function registerEmotionModule(name: string, version: string) {
+  if (versions[name] && versions[name] !== version) {
+    console.warn(
+      `Package ${name}@${
+        versions[name]
+      } is already registered. Running ${version} may cause problems.`
+    )
+  }
+  versions[name] = version
+}
+
+registerEmotionModule(
+  require('../package.json').name,
+  require('../package.json').version
+)
 
 export function getRegisteredStyles(
   registered: RegisteredCache,

scripts/babel-preset-emotion-dev/package.json

@@ -10,6 +10,7 @@
     "@babel/plugin-proposal-class-properties": "^7.7.0",
     "@babel/plugin-transform-flow-strip-types": "^7.6.3",
     "babel-plugin-add-basic-constructor-for-react-components": "^0.1.0",
-    "babel-plugin-fix-dce-for-classes-with-statics": "^0.1.0"
+    "babel-plugin-fix-dce-for-classes-with-statics": "^0.1.0",
+    "babel-plugin-inline-package-json": "^2.0.0"
   }
 }

scripts/babel-preset-emotion-dev/src/index.js

@@ -18,7 +18,8 @@ module.exports = () => {
       [
         require.resolve('@babel/plugin-proposal-class-properties'),
         { loose: true }
-      ]
+      ],
+      require.resolve('babel-plugin-inline-package-json')
     ]
   }
 }

yarn.lock

@@ -4429,6 +4429,11 @@ babel-plugin-fix-dce-for-classes-with-statics@^0.1.0:
   resolved "https://registry.npmjs.org/babel-plugin-fix-dce-for-classes-with-statics/-/babel-plugin-fix-dce-for-classes-with-statics-0.1.0.tgz#9cac930cfb50a879d66cd5dc3bd4af731c1ecb90"
   integrity sha512-nya9Uw5te1kWNXGodrftTNQwx3oyPEQWOgg/k0tzViExKv6L1BoyNI0+rkin+FiF1Kp5ZjURjBnuJg/1n8erLA==
 
+babel-plugin-inline-package-json@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/babel-plugin-inline-package-json/-/babel-plugin-inline-package-json-2.0.0.tgz#1f9558d96667f4b8787e807d764e6e15b4f0cd07"
+  integrity sha1-H5VY2WZn9Lh4foB9dk5uFbTwzQc=
+
 babel-plugin-istanbul@^4.0.0, babel-plugin-istanbul@^4.1.6:
   version "4.1.6"
   resolved "https://registry.npmjs.org/babel-plugin-istanbul/-/babel-plugin-istanbul-4.1.6.tgz#36c59b2192efce81c5b378321b74175add1c9a45"