• This is a bug (maybe?)
• This is a modification request

After upgrading to Webpack 5 and webpack-dev-server, my yarn start script take 3 times longer then with Webpack 4. I always returned back to old Webpack. But now I probably found a error which cause such a slowdown.

Probably problematics code:
https://github.com/webpack/webpack-dev-server/blob/master/lib/Server.js#L1017

Expected Behavior

No code is watched (I think same as in Webpack 4 by default)

Actual Behavior

staticOption.watch is actualy an empty object (https://github.com/webpack/webpack-dev-server/blob/master/lib/Server.js#L182) so the condition passes, then webpack-dev-server try to watch the whole project (if you have static directory set to root - even your node-modules are watched). It takes so much time in a larger project.

Workaround Code

devServer: { static: { watch: false } }

If you set watch to false, no empty object will be used and your bundle will be much faster (280s -> 80s for me, Webpack v4 120s).