Compacting nested colors sometimes uses the wrong color

[rymiel]

I don't know the extent of the bug but at the very least: Compacting a component with nested children, where one child-of-a-child uses the color of the outer-most element will incorrectly use the color of the child instead.

Consider the following test case:

  @Test
  void testSomethingIdk() {
    final Component notCompact = text("mew", NamedTextColor.RED)
      .append(text("mow", NamedTextColor.BLUE)
          .append(text("mew", NamedTextColor.RED)));
    final Component expectedCompact = text("mew", NamedTextColor.RED)
      .append(text("mow", NamedTextColor.BLUE))
      .append(text("mew"));

    assertEquals(notCompact.compact(), expectedCompact);
  }

Currently, this test fails because the last "mew" turns blue.

The second component is joined into "mowmew" in blue, but those should never be joined as they are different colors

[rymiel]

I've noticed that swapping the order of childParentStyle and parentStyle here will produce a suboptimal tree, but at least keeps the operation as monotonic. I can't wrap my head around all of the parent and child logic but this is where the mistake is coming from; the style of red color is merged into blue with IF_ABSENT_ON_TARGET, so the blue color "wins"

adventure/api/src/main/java/net/kyori/adventure/text/ComponentCompaction.java

Line 71 in 2497d92

childParentStyle = parentStyle.merge(childParentStyle, Style.Merge.Strategy.IF_ABSENT_ON_TARGET);

[zml2008]

Your change there does appear to be correct. It doesn't look like the compaction algorithm has a way to promote a child to a sibling -- adding that would probably be an interesting feature, but I'd rather prioritize correctness for now.

It seems like all other tests pass with that change though, so I think it's worth applying it for now.