Recently, minecraft:horizontal_tree_decoration_feature was introduced to decorate features with things like vines. Unfortunately, this feature type is near-worthless to creators: places_block’s block is required to have both the cardinal_direction and growth block states. Almost no blocks in Vanilla have both of these states, and it’s impossible for a custom block to have the proper growth state.

Realistically, this feature should accept any block and auto-rotate dynamically. Another property could then also be given to control growth state application. Alternatively, places_block could be a weighted list like single block features support.

Demonstration

The attached screenshot demonstrates this issue. The content log errors show the state requirements. The associated feature is as follows:

{
  "format_version": "1.26.50",
  "minecraft:horizontal_tree_decoration_feature": {
    "description": {"identifier": "bug_features:horizontal_tree_decoration_feature"},
    
    "places_block": "minecraft:obsidian",
    "bark_side_only": true,
    "allow_adjacent": true
  }
}

Reproduction

The demo screenshot and code are taken from the behavior pack in the attached world for convenience. This world can be opened (in Minecraft Preview) for inspection or unzipped to access the code associated with such.