Prevent unhandled promises in createAsyncThunk

jest.config.js

@@ -0,0 +1,3 @@
+module.exports = {
+  setupFilesAfterEnv: ['./jest.setup.js']
+}

jest.setup.js

@@ -0,0 +1,4 @@
+process.on('unhandledRejection', error => {
+  // eslint-disable-next-line no-undef
+  fail(error)
+})

src/createAsyncThunk.test.ts

@@ -549,6 +549,21 @@ describe('conditional skipping of asyncThunks', () => {
     expect(dispatch).toHaveBeenCalledTimes(0)
   })
 
+  test('does not fail when attempting to abort a canceled promise', async () => {
+    const asyncPayloadCreator = jest.fn(async (x: typeof arg) => {
+      await new Promise(resolve => setTimeout(resolve, 2000))
+      return 10
+    })
+
+    const asyncThunk = createAsyncThunk('test', asyncPayloadCreator, {
+      condition
+    })
+    const promise = asyncThunk(arg)(dispatch, getState, extra)
+    promise.abort(
+      `If the promise was 1. somehow canceled, 2. in a 'started' state and 3. we attempted to abort, this would crash the tests`
+    )
+  })
+
   test('rejected action can be dispatched via option', async () => {
     const asyncThunk = createAsyncThunk('test', payloadCreator, {
       condition,

src/createAsyncThunk.ts

@@ -326,9 +326,12 @@ If you want to use the AbortController to react to \`abort\` events, please cons
         )
       )
 
+      let started = false
       function abort(reason?: string) {
-        abortReason = reason
-        abortController.abort()
+        if (started) {
+          abortReason = reason
+          abortController.abort()
+        }
       }
 
       const promise = (async function() {
@@ -344,6 +347,7 @@ If you want to use the AbortController to react to \`abort\` events, please cons
               message: 'Aborted due to condition callback returning false.'
             }
           }
+          started = true
           dispatch(pending(requestId, arg))
           finalAction = await Promise.race([
             abortedPromise,