Fix issue with missing chunks when handling multiple configuration.

[TomekStaszkiewicz]

See #96

I checked what changed from version 0.4.3 and I noticed that back then the small library deep-extend was used to extend resulting contents.
In version 1.0.0 it was replaced by small util assign, but I believe that someone made a small mistake, and actually the util assignin was meant to be used. After changing to that it seems to be working.

[TomekStaszkiewicz]

I was wrong with using the assignin - it is not working as the deep-merge mechanism. It is performing only a shallow merge. I think that using lodash.merge is the best solution for this one

[joaopslins]

Hi @TomekStaszkiewicz

Thanks for the reproduction and the PR! Would you mind adding some regression tests for this use case of multiple export configurations? Both for webpack 4 and webpack 5? If you aren't able to do that please let us know so we can work on it. Thanks!

[joaopslins]

I believe this should not be changed, since it is part of the tests. The fixes you had to make in the tests are caused by this, not by changing assign to merge in the _writeOutput method.

I actually find it weird that this change is affecting the current tests, but I'd like for this PR to focus on one matter at a time. If you could please revert this specific change (and the tests), or provide a reason for that change, it would be great.

[andersk]

This has caused unexpected duplication after webpack-dev-server hot updates, due to the following behavior of lodash.merge:

> chunks = { main: ['a', 'b', 'c', 'd', 'e'] } { main: [ 'a', 'b', 'c', 'd', 'e' ] } > merge(chunks, { main: ['foo', 'bar'] }) { main: [ 'foo', 'bar', 'c', 'd', 'e' ] }

Opened #101 to fix this.