---
- name: Block Mapping with Missing Keys
  from: NimYAML tests
  tags: duplicate-key mapping empty-key
  yaml: |
    : a
    : b
  tree: |
    +STR
     +DOC
      +MAP
       =VAL :
       =VAL :a
       =VAL :
       =VAL :b
      -MAP
     -DOC
    -STR