client javascript doesn't reload the page if there's a build-time error on first load

[hexpunk]

• Operating System: MacOS High Sierra, Ubuntu 16.04
• Node Version: 8.9.4
• NPM Version: 5.6.0
• webpack Version: 3.11.0
• webpack-dev-server Version: 2.11.1

• This is a bug
• This is a modification request

Code

I've made a repository that minimally recreates this issue. JayAndCatchFire/minimal-wds-bug-example

Expected Behavior

Scenario 1

1. The user's code being packed with webpack has a build-time error in it.
2. The user starts webpack-dev-server and navigates to the app in their browser. The app doesn't fully load due to the build-time error.
3. The build-time error in the user's code is corrected and webpack successfully rebuilds the bundle.
4. Webpack-dev-server should reload the app page with the newly built code.

Scenario 2

1. The user has been running webpack-dev-server for a bit and introduces a code change in their code that includes a build-time error.
2. The user navigates to their app in a browser with a fresh tab at this point or manually hard-reloads the page at this point. The app doesn't fully load due to the build-time error.
3. The build-time error in the user's code is corrected and webpack successfully rebuilds the bundle.
4. Webpack-dev-server should reload the app page with the newly built code.

Actual Behavior

In both of the above scenarios, the fourth step doesn't occur. The page remains in a broken state.

For Bugs; How can we reproduce the behavior?

The steps outlined in the scenarios above should outline how to reproduce the bug reliably, although I give more detailed instructions in the README file in my example repository.

[hexpunk]

I believe the reason this is happening is because of the initial variable in the client source. I suspect it's the culprit because if you correct the client code that's causing a built-time error, reintroduce the erroneous code, and then remove it a second time, the app will be reloaded as expected.

[SpaceK33z]

Hey I'm working on this right now and looking through your issue and PR, and I just want to say: THANK YOU for looking into this so extensively and making an example repo. I'm going through it to first reproduce your bug and then test your fix.

[hexpunk]

You're very welcome. I'd really love to add some unit tests to my PR, but the client code doesn't seem to have any tests that I could find. I'd love any help or guidance you could give me as to the best way to unit test that code.

[SpaceK33z]

Yeah there are no unit tests for the client code (yet). If you want to help setup tests for the client code that would be welcome though, I see two ways to tackle this:

• Switch to the Jest test runner and run the client code through its fake DOM.
• Let the tests start a Puppeteer (headless Chrome) instance, connect to it and run the client code tests in the headless browser.