contenthash generates same filename for different contents

• Operating System: macOS 10.14.6
• Node Version: v8.11.2
• NPM Version: 6.0.1
• webpack Version: 4.41.2
• mini-css-extract-plugin Version: 0.8.0

Expected Behavior

Should generate different filename when content is changed.

Actual Behavior

Same filename was generated when content is updated.

How Do We Reproduce?

https://github.com/zlk89/webpack-css-contenthash-diff

• yarn to install packages
• yarn build
• under dist folder, you will find two css files with same content hash, while content is different.

Basically contenthash is same, when import statement order is different:

// in js
@import 'a.scss';
@import 'b.scss';

// in js
@import 'b.scss';
@import 'a.scss';

[zlk89]

verified the bug has been fixed

[zlk89]

^ bump, this bug essentially prevents us from utilizing long term cache on all css generated by this plugin