Highlighting "flickering" while applying formatting

[jonkri]

Under some circumstances, lines lose their syntax highlighting for a while when formatting is applied.

The attached image illustrates it.

I would like for the text not to temporarily turn to the foreground color.

[SpiderPig]

This has to do with the way it applies the formatting. It could probably benefit from the way prettier-js and go-mode/gofmt work. They compute the differences and then apply the changes by spot patching the contents without rewriting the entire buffer. It also protects the undo history.