fix: Suppress unhandled rejections (#59)

Suppress unhandled rejections

Author: chrisbreiding

.gitignore

@@ -1,3 +1,4 @@
 node_modules/
 .DS_Store
 *.log*
+_test-output

__snapshots__/e2e_spec.js

@@ -5,7 +5,7 @@ const debug = require('debug')('cypress:webpack')
 const createDeferred = require('./deferred')
 const stubbableRequire = require('./stubbable-require')
 
-const bundles = {}
+let bundles = {}
 
 // we don't automatically load the rules, so that the babel dependencies are
 // not required if a user passes in their own configuration
@@ -148,12 +148,20 @@ const preprocessor = (options = {}) => {
       // we overwrite the latest bundle, so that a new call to this function
       // returns a promise that resolves when the bundling is finished
       latestBundle = createDeferred()
-      bundles[filePath] = latestBundle.promise.tap(() => {
+      bundles[filePath] = latestBundle.promise
+
+      bundles[filePath].tap(() => {
         debug('- compile finished for', filePath)
         // when the bundling is finished, emit 'rerun' to let Cypress
         // know to rerun the spec
         file.emit('rerun')
       })
+      // we suppress unhandled rejections so they don't bubble up to the
+      // unhandledRejection handler and crash the process. Cypress will
+      // eventually take care of the rejection when the file is requested.
+      // note that this does not work if attached to latestBundle.promise
+      // for some reason. it only works when attached after .tap  ¯\_(ツ)_/¯
+      .suppressUnhandledRejections()
     }
 
     // when we should watch, we hook into the 'compile' hook so we know when
@@ -200,4 +208,9 @@ Object.defineProperty(preprocessor, 'defaultOptions', {
   },
 })
 
+// for testing purposes
+preprocessor.__reset = () => {
+  bundles = {}
+}
+
 module.exports = preprocessor

index.js

@@ -28,8 +28,11 @@
     "pretest": "npm run lint",
     "secure": "nsp check",
     "size": "t=\"$(npm pack .)\"; wc -c \"${t}\"; tar tvf \"${t}\"; rm \"${t}\";",
-    "test": "mocha",
-    "test-watch": "chokidar '*.js' 'test/*.js' -c 'mocha'",
+    "test": "npm run test-unit && npm run test-e2e",
+    "test-e2e": "mocha test/e2e/*.js",
+    "test-unit": "mocha test/unit/*.js",
+    "test-debug": "node --inspect --debug-brk ./node_modules/.bin/_mocha",
+    "test-watch": "chokidar '*.js' 'test/unit/*.js' -c 'npm run test-unit'",
     "semantic-release": "semantic-release pre && npm publish --access public && semantic-release post"
   },
   "devDependencies": {
@@ -46,6 +49,7 @@
     "eslint": "4.6.1",
     "eslint-plugin-cypress-dev": "1.1.1",
     "eslint-plugin-mocha": "4.11.0",
+    "fs-extra": "8.1.0",
     "github-post-release": "1.13.1",
     "license-checker": "13.0.3",
     "mocha": "3.5.0",
@@ -56,6 +60,7 @@
     "simple-commit-message": "3.3.1",
     "sinon": "3.2.1",
     "sinon-chai": "2.13.0",
+    "snap-shot-it": "7.9.0",
     "webpack": "^4.18.1"
   },
   "peerDependencies": {
@@ -67,8 +72,8 @@
     "babel-loader": "^8.0.2"
   },
   "dependencies": {
-    "bluebird": "3.5.0",
-    "debug": "3.1.0"
+    "bluebird": "3.7.1",
+    "debug": "4.1.1"
   },
   "release": {
     "verifyConditions": "condition-circle",

package.json

@@ -0,0 +1,59 @@
+const EventEmitter = require('events').EventEmitter
+const expect = require('chai').expect
+const fs = require('fs-extra')
+const path = require('path')
+const snapshot = require('snap-shot-it')
+
+const preprocessor = require('../../index')
+
+describe('webpack preprocessor - e2e', () => {
+  const outputPath = path.join(__dirname, '..', '_test-output', 'output.js')
+
+  let file
+  let filePath
+
+  beforeEach(() => {
+    const originalFilePath = path.join(__dirname, '..', 'fixtures', 'example_spec.js')
+
+    filePath = path.join(__dirname, '..', '_test-output', 'example_spec.js')
+
+    preprocessor.__reset()
+    fs.removeSync(path.join(__dirname, '_test-output'))
+    fs.outputFileSync(filePath, '')
+    fs.copyFileSync(originalFilePath, filePath)
+
+    file = Object.assign(new EventEmitter(), {
+      filePath,
+      outputPath,
+    })
+  })
+
+  it('correctly preprocesses the file', () => {
+    return preprocessor()(file).then(() => {
+      snapshot(fs.readFileSync(outputPath).toString())
+    })
+  })
+
+  it('allows attaching catch later on syntax error without triggering unhandled rejection', (done) => {
+    process.on('unhandledRejection', (err) => {
+      // eslint-disable-next-line no-console
+      console.error('Unhandled Rejection:', err.stack)
+      done('Should not have trigger unhandled rejection')
+    })
+
+    file.shouldWatch = true
+
+    preprocessor()(file).then(() => {
+      fs.outputFileSync(filePath, '{')
+
+      setTimeout(() => {
+        preprocessor()(file)
+        .catch((err) => {
+          expect(err.stack).to.include('Unexpected token')
+          file.emit('close')
+          done()
+        })
+      }, 1000)
+    })
+  })
+})

test/e2e/e2e_spec.js

@@ -0,0 +1,6 @@
+it('is a test', () => {
+  const [a, b] = [1, 2]
+  expect(a).to.equal(1)
+  expect(b).to.equal(2)
+  expect(Math.min(...[3, 4])).to.equal(3)
+})

test/fixtures/example_spec.js

@@ -14,8 +14,8 @@ mockery.enable({
 })
 mockery.registerMock('webpack', webpack)
 
-const preprocessor = require('../index')
-const stubbableRequire = require('../stubbable-require')
+const preprocessor = require('../../index')
+const stubbableRequire = require('../../stubbable-require')
 
 describe('webpack preprocessor', function () {
   beforeEach(function () {