thread-loader's 'poolTimeout' should be overridden when watching

[edmorley]

Hi!

Currently create-react-app uses thread-loader with default options in both the development and production configs:

create-react-app/packages/react-scripts/config/webpack.config.dev.js

Lines 211 to 213 in bf3d73c

	// This loader parallelizes code compilation, it is optional but
	// improves compile time on larger projects
	require.resolve('thread-loader'),

create-react-app/packages/react-scripts/config/webpack.config.prod.js

Lines 237 to 239 in bf3d73c

	// This loader parallelizes code compilation, it is optional but
	// improves compile time on larger projects
	require.resolve('thread-loader'),

The production usage is fine, however as mentioned here, when watching is enabled (ie the development config with webpack-dev-server) the poolTimeout option should be changed from its default of 500 ms to Infinity to avoid paying the overhead of worker startup on every rebuild.

See:
https://github.com/webpack-contrib/thread-loader#examples

[gaearon]

Want to send a PR?