suppress unhandled rejections from update bundles

if we don’t suppress unhandled rejections, it gets caught by process.on(‘unhandledRejection’) and crashes the app. it’s okay to suppress the rejection because the promise will eventually be handled by the app

Author: chrisbreiding

index.js

@@ -146,16 +146,21 @@ const preprocessor = (options = {}) => {
       })
     }
 
-    // when we're notified of an update via watchify, signal for Cypres to
+    // when we're notified of an update via watchify, signal for Cypress to
     // rerun the spec
     bundler.on('update', () => {
       log(`update ${filePath}`)
       // we overwrite the cached bundle promise, so on subsequent invocations
       // it gets the latest bundle
-      bundles[filePath] = bundle().tap(() => {
+      const bundlePromise = bundles[filePath] = bundle()
+      .finally(() => {
         log(`- update finished for ${filePath}`)
         config.emit('rerun')
       })
+      // we suppress unhandled rejections so they don't bubble up to the
+      // unhandledRejection handler and crash the app. Cypress will eventually
+      // take care of the rejection when the file is requested
+      bundlePromise.suppressUnhandledRejections()
     })
 
     const bundlePromise = fs.ensureDirAsync(path.dirname(outputPath)).then(bundle)

package.json

@@ -30,6 +30,7 @@
     "secure": "nsp check",
     "size": "t=\"$(npm pack .)\"; wc -c \"${t}\"; tar tvf \"${t}\"; rm \"${t}\";",
     "test": "mocha",
+    "test-debug": "node --inspect --debug-brk ./node_modules/.bin/_mocha",
     "test-watch": "chokidar '*.js' 'test/*.js' -c 'npm test'"
   },
   "release": {

test/index_spec.js

@@ -211,7 +211,7 @@ describe('browserify preprocessor', function () {
         })
       })
 
-      it('closes bundler when shouldWatc is true and `close` is emitted', function () {
+      it('closes bundler when shouldWatch is true and `close` is emitted', function () {
         this.config.shouldWatch = true
         return this.run().then(() => {
           this.config.on.withArgs('close').yield()
@@ -254,6 +254,42 @@ describe('browserify preprocessor', function () {
           expect(err.originalStack).to.equal(this.err.stack)
         })
       })
+
+      it('does not trigger unhandled rejection when bundle errors after update', function (done) {
+        const handler = sandbox.spy()
+        process.on('unhandledRejection', handler)
+        this.createWriteStreamApi.on.withArgs('finish').onFirstCall().yields()
+
+        this.config.emit = () => {
+          setTimeout(() => {
+            expect(handler).not.to.be.called
+            process.removeListener('unhandledRejection', handler)
+            done()
+          }, 500)
+        }
+
+        this.run().then(() => {
+          streamApi.on.withArgs('error').yieldsAsync(new Error('bundle error')).returns({ pipe () {} })
+          this.bundlerApi.on.withArgs('update').yield()
+        })
+      })
+
+      it('rejects subsequent request after and update bundle errors', function () {
+        this.createWriteStreamApi.on.withArgs('finish').onFirstCall().yields()
+        const run = preprocessor(this.options)
+        return run(this.config)
+        .then(() => {
+          streamApi.on.withArgs('error').yieldsAsync(new Error('bundle error')).returns({ pipe () {} })
+          this.bundlerApi.on.withArgs('update').yield()
+          return run(this.config)
+        })
+        .then(() => {
+          throw new Error('should not resolve')
+        })
+        .catch((err) => {
+          expect(err.message).to.contain('bundle error')
+        })
+      })
     })
   })
 })