yq/pkg/yqlib/doc/operators/anchor-and-alias-operators.md

Anchor and Alias Operators

Use the alias and anchor operators to read and write yaml aliases and anchors. The explode operator normalises a yaml file (dereference (or expands) aliases and remove anchor names).

yq supports merge aliases (like <<: *blah) however this is no longer in the standard yaml spec (1.2) and so yq will automatically add the !!merge tag to these nodes as it is effectively a custom tag.

Dereference and update a field

Use explode with multiply to dereference an object

Given a sample.yml file of:

item_value: &item_value
  value: true
thingOne:
  name: item_1
  !!merge <<: *item_value
thingTwo:
  name: item_2
  !!merge <<: *item_value

then

yq '.thingOne |= explode(.) * {"value": false}' sample.yml

will output

item_value: &item_value
  value: true
thingOne: false
thingTwo:
  name: item_2
  !!merge <<: *item_value