YAML does *not* support unsplatting/merging lists

15 August, 2025 at 21:19 • 1 min read

YAML does not support unsplatting lists (basically, merging list items inline like you can with objects) and that’s intentional.

So if you have a document like below, there is no syntax to make the commands a three item list:

---
example: &example
  - "Hello"
  - "World!"

name: "hello"
commands:
  - << *example
  - "Oho!"

WILL NOT turn into:

---
example: &example
  - "Hello"
  - "World!"

name: "hello"
commands:
  - "Hello"
  - "World!"
  - "Oho!"

…and just because before I found the issue where it was described that this isn’t happening I had made a test repo to try and understand if it was a library/usage issue, because I noticed I could get things running on CI with << *example which syntax didn’t give syntax error, but also did nothing when running on Drone CI.

#yaml