Fix for multiple compilations/webpack-dev-server

[jeffposnick]

R: @philipwalton

Fixes #2158

The nuance about emit getting called multiple times on the same plugin instance was lost in the v5 rewrite. This makes sure that we don't modify the this.config member variable in our emit callback, allowing the callback to work when called multiple times via, e.g., webpack-dev-server.

[philipwalton]

👍

[simonsinclair]

@jeffposnick, thanks for fixing this. Is there any way I can test this change in my project today?

[jeffposnick]

We should be cutting a new alpha release next week, but if you need the fix sooner, checking out the https://github.com/GoogleChrome/workbox repo and running npm install && gulp build should give you a local copy of everything.

They you can reference workbox-webpack-plugin from <git-clone-root>/packages/workbox-webpack-plugin inside of your webpack config.

[simonsinclair]

That worked, thanks! Looking forward to the new alpha when it lands.