Lowdefy Snippet for Merging Object Arrays

array_merge.yaml

#
# Array merge takes a source array of objects and merges into into a
# destination array of objects, while looking up an defined attribute from each
# object (in both arrays) to de-duplicate the final array.
#
# So if you call with:
#  _ref:
#    path: path/to/array_merge.yaml
#    vars:
#      from: [ {"id": 1, name: "Alice"}, {"id": 2, name: "Bob"} ]
#      into: [ {"id": 2, name: "Robert"}, {"id": 3, name: "Charlie"} ]
#      key: id
#
# ... it will resolve to:
#
#  [ {"id": 1, name: "Alice"}, {"id": 2, name: "Robert"}, {"id": 3, name: Charlie} ]
#
# ... noting that the attributes of 2 took precedence from the values of "into".
---
# Convert {"id1": {on_key: "id1", attr: "a"}} to [{on_key: "id1", attr: "a"}].
_object.values:
  # Deduplicate-merge objects {"id1": {on_key: "id1", attr: "a"}} into {"id1": {on_key: "id1", attr: "a"}}.
  _object.assign:
    # Convert [ ["id1", {on_key: "id1", attr: "a"} ] ] to {"id1": {on_key: "id1", attr: "a"}}
    - _object.fromEntries:
        # Convert [ {on_key: "id1", attr: "a"} ] into [ ["id1", {on_key: "id1", attr: "a"} ] ]
        _array.map:
          'on':
            _var: into
          callback:
            # Convert {on_key: "id1", attr: "a"} into ["id1", {on_key: "id1", attr: "a"} ]
            _function:
              - __get:
                  # Get the *value* of the primary key (passed as the 'on'
                  # var).
                  from:
                    __args: 0
                  key:
                    _var: key
              - __args: 0
    # Same exact process but with the "from" var.
    - _object.fromEntries:
        _array.map:
          'on':
            _var: from
          callback:
            _function:
              - __get:
                  from:
                    __args: 0
                  key:
                    _var: key
              - __args: 0