Modify 'import css' order more than 2 times, it will not work

• Operating System:mac os 10.14.4
• Node Version:8.9.0
• NPM Version:6.8.0
• webpack Version:4.16.5
• mini-css-extract-plugin Version:0.7.0

Expected Behavior

when I use webpack-dev-server. I modify css order. The out css should be modified at the same time. For example:

import 'a.less';
import 'b.less';

out:

.a{
}
.b{
}

modify:

import 'b.less';
import 'a.less';

out:

.b{
}
.a{
}

Actual Behavior

Only the first modification works. Don’t work from the second time. For example:

import 'a.less';
import 'b.less';

out:

.a{
}
.b{
}

modify:

import 'b.less';
import 'a.less';

out:

.b{
}
.a{
}

modify:

import 'a.less';
import 'b.less';

out:

.b{
}
.a{
}

not change

How Do We Reproduce?

Modify import more than 2 times

[alexander-akait]

Please create minimum reproducible test repo

[alexander-akait]

Fixed for webpack v5 and v1.3.8