Extends the tree walker with an options paramater allowing you to define whether componentWillUnmount should be called or not.

Author: ctrlplusb

src/__tests__/index.test.js

@@ -111,20 +111,31 @@ describe('reactTreeWalker', () => {
       }
     }
 
-    const tree = <Baz />
-    // eslint-disable-next-line no-unused-vars
-    const visitor = (element, instance, context) => {
-      if (instance) {
-        return true
-      }
-      return true
-    }
-    return reactTreeWalker(tree, visitor).then(() => {
+    return reactTreeWalker(<Baz />, () => true).then(() => {
       const expected = { foo: 'bar' }
       expect(actual).toMatchObject(expected)
     })
   })
 
+  it('calls componentWillUnmount and does not fail if it errors', () => {
+    let called = true
+
+    class Baz extends Component {
+      componentWillUnmount() {
+        called = true
+        throw new Error('An error during unmount')
+      }
+
+      render() {
+        return <div>foo</div>
+      }
+    }
+
+    return reactTreeWalker(<Baz />, () => true, null, { componentWillUnmount: true }).then(() => {
+      expect(called).toBeTruthy()
+    })
+  })
+
   it('getChildContext', () => {
     class Baz extends Component {
       props: { children?: any };
@@ -144,9 +155,7 @@ describe('reactTreeWalker', () => {
     Qux.contextTypes = { foo: React.PropTypes.string.isRequired }
 
     const tree = <Baz><Qux /></Baz>
-    // eslint-disable-next-line no-unused-vars
-    const visitor = (element, instance, context) => undefined
-    return reactTreeWalker(tree, visitor).then(() => {
+    return reactTreeWalker(tree, () => true).then(() => {
       const expected = { foo: 'bar' }
       expect(actual).toMatchObject(expected)
     })

src/index.js

@@ -7,6 +7,10 @@
 // eslint-disable-next-line import/no-extraneous-dependencies
 import { Children } from 'react'
 
+const defaultOptions = {
+  componentWillUnmount: false,
+}
+
 // Lifted from https://github.com/sindresorhus/p-reduce
 // Thanks @sindresorhus!
 const pReduce = (iterable, reducer, initVal) =>
@@ -49,7 +53,7 @@ export const isPromise = x => x != null && typeof x.then === 'function'
 // Recurse an React Element tree, running visitor on each element.
 // If visitor returns `false`, don't call the element's render function
 // or recurse into its child elements
-export default function reactTreeWalker(element, visitor, context) {
+export default function reactTreeWalker(element, visitor, context, options = defaultOptions) {
   return new Promise((resolve) => {
     const doVisit = (getChildren, visitorResult, childContext, isChildren) => {
       const doTraverse = (shouldContinue) => {
@@ -129,7 +133,21 @@ export default function reactTreeWalker(element, visitor, context) {
               instance.componentWillMount()
             }
 
-            return instance.render()
+            const children = instance.render()
+
+            if (options.componentWillUnmount && instance.componentWillUnmount) {
+              try {
+                instance.componentWillUnmount()
+              } catch (err) {
+                // This is an experimental feature, we don't want to break
+                // the bootstrapping process, but lets warn the user it
+                // occurred.
+                console.warn('Error calling componentWillUnmount whilst walking your react tree')
+                console.warn(err)
+              }
+            }
+
+            return children
           },
           visitor(element, instance, context),
           () =>