Minifier: Drop Redundant Doubled Properties?

Hi @devongovett ! 👋 First of all, thanks for all of your effort on this, really amazing for the community to have such a great tool!

I was looking for a feature of @parcel/css that would allow for removal of duplicate properties.

For example:

Input

div {
  color: green;
  color: red;
}

@parcel/css Output (Playground Link)

div{color:green;color:red}

Expected Output

div{color:red}

However, it could be a problem with my understanding of the CSS spec somehow, because I see that some duplicated properties do indeed get dropped:

Input

div {
  background: green;
  background: red;
}

@parcel/css Output (Playground Link)

div{background:red}

Start with the two CSS examples and their linked @parcel/css Playground outputs, then check the CSS specification rules for removing earlier declarations without changing fallback behavior. Done means redundant doubled properties such as color are safely removed while valid duplicate-declaration cases remain preserved, matching the expected output.