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.

NOTE --yaml-fix-merge-anchor-to-spec flag

yq doesn't merge anchors <<: to spec, in some circumstances it incorrectly overrides existing keys when the spec documents not to do that.

To minimise disruption while still fixing the issue, a flag has been added to toggle this behaviour. This will first default to false; and log warnings to users. Then it will default to true (and still allow users to specify false if needed).

This flag also enables advanced merging, like inline maps, as well as fixes to ensure when exploding a particular path, neighbours are not affect ed.

Long story short, you should be setting this flag to true.

See examples of the flag differences below, where LEGACY is with the flag off; and FIXED is with the flag on.

Merge one map

see https://yaml.org/type/merge.html

Given a sample.yml file of:

- &CENTER
  x: 1
  y: 2
- &LEFT
  x: 0
  y: 2
- &BIG

then

yq '.[4] | explode(.)' sample.yml

will output

x: 1
y: 2
r: 10

Get anchor

Given a sample.yml file of:

a: &billyBob cat

then

yq '.a | anchor' sample.yml

will output

billyBob

Set anchor

Given a sample.yml file of:

a: cat

then

yq '.a anchor = "foobar"' sample.yml

will output

a: &foobar cat

Set anchor relatively using assign-update

Given a sample.yml file of:

a:
  b: cat

then

yq '.a anchor |= .b' sample.yml

will output

a: &cat
  b: cat

Get alias

Given a sample.yml file of:

b: &billyBob meow
a: *billyBob

then

yq '.a | alias' sample.yml

will output

billyBob

Set alias

Given a sample.yml file of:

b: &meow purr
a: cat

then

yq '.a alias = "meow"' sample.yml

will output

b: &meow purr
a: *meow

Set alias to blank does nothing

Given a sample.yml file of:

b: &meow purr
a: cat

then

yq '.a alias = ""' sample.yml

will output

b: &meow purr
a: cat

Set alias relatively using assign-update

Given a sample.yml file of:

b: &meow purr
a:
  f: meow

then

yq '.a alias |= .f' sample.yml

will output

b: &meow purr
a: *meow

Explode alias and anchor

Given a sample.yml file of:

f:
  a: &a cat
  b: *a

then

yq 'explode(.f)' sample.yml

will output

f:
  a: cat
  b: cat

Explode with no aliases or anchors

Given a sample.yml file of:

a: mike

then

yq 'explode(.a)' sample.yml

will output

a: mike

Explode with alias keys

Given a sample.yml file of:

f:
  a: &a cat
  *a: b

then

yq 'explode(.f)' sample.yml

will output

f:
  a: cat
  cat: b

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(.) | sort_keys(.)) * {"value": false}' sample.yml

will output

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

LEGACY: Explode with merge anchors

Caution: this is for when --yaml-fix-merge-anchor-to-spec=false; it's not to YAML spec because the merge anchors incorrectly override the object values (foobarList.b is set to bar_b when it should still be foobarList_b). Flag will default to true in late 2025

Given a sample.yml file of:

foo: &foo
  a: foo_a
  thing: foo_thing
  c: foo_c
bar: &bar
  b: bar_b
  thing: bar_thing
  c: bar_c
foobarList:
  b: foobarList_b
  !!merge <<:
    - *foo
    - *bar
  c: foobarList_c
foobar:
  c: foobar_c
  !!merge <<: *foo
  thing: foobar_thing

then

yq 'explode(.)' sample.yml

will output

foo:
  a: foo_a
  thing: foo_thing
  c: foo_c
bar:
  b: bar_b
  thing: bar_thing
  c: bar_c
foobarList:
  b: bar_b
  thing: foo_thing
  c: foobarList_c
  a: foo_a
foobar:
  c: foo_c
  a: foo_a
  thing: foobar_thing

LEGACY: Merge multiple maps

see https://yaml.org/type/merge.html. This has the correct data, but the wrong key order; set --yaml-fix-merge-anchor-to-spec=true to fix the key order.

Given a sample.yml file of:

- &CENTER
  x: 1
  y: 2
- &LEFT
  x: 0
  y: 2
- &BIG
  r: 10
- &SMALL
  r: 1
- !!merge <<:
    - *CENTER
    - *BIG

then

yq '.[4] | explode(.)' sample.yml

will output

r: 10
x: 1
y: 2

LEGACY: Override

see https://yaml.org/type/merge.html. This has the correct data, but the wrong key order; set --yaml-fix-merge-anchor-to-spec=true to fix the key order.

Given a sample.yml file of:

- &CENTER
  x: 1
  y: 2
- &LEFT
  x: 0
  y: 2
- &BIG
  r: 10
- &SMALL
  r: 1
- !!merge <<:
    - *BIG
    - *LEFT
    - *SMALL
  x: 1

then

yq '.[4] | explode(.)' sample.yml

will output

r: 10
x: 1
y: 2

FIXED: Explode with merge anchors

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour (flag will default to true in late 2025). Observe that foobarList.b property is still foobarList_b.

Given a sample.yml file of:

foo: &foo
  a: foo_a
  thing: foo_thing
  c: foo_c
bar: &bar
  b: bar_b
  thing: bar_thing
  c: bar_c
foobarList:
  b: foobarList_b
  !!merge <<:
    - *foo
    - *bar
  c: foobarList_c
foobar:
  c: foobar_c
  !!merge <<: *foo
  thing: foobar_thing

then

yq 'explode(.)' sample.yml

will output

foo:
  a: foo_a
  thing: foo_thing
  c: foo_c
bar:
  b: bar_b
  thing: bar_thing
  c: bar_c
foobarList:
  b: foobarList_b
  a: foo_a
  thing: foo_thing
  c: foobarList_c
foobar:
  c: foobar_c
  a: foo_a
  thing: foobar_thing

FIXED: Merge multiple maps

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour (flag will default to true in late 2025). Taken from https://yaml.org/type/merge.html. Same values as legacy, but with the correct key order.

Given a sample.yml file of:

- &CENTER
  x: 1
  y: 2
- &LEFT
  x: 0
  y: 2
- &BIG
  r: 10
- &SMALL
  r: 1
- !!merge <<:
    - *CENTER
    - *BIG

then

yq '.[4] | explode(.)' sample.yml

will output

x: 1
y: 2
r: 10

FIXED: Override

Given a sample.yml file of:

- &CENTER
  x: 1
  y: 2
- &LEFT
  x: 0
  y: 2
- &BIG
  r: 10
- &SMALL
  r: 1
- !!merge <<:
    - *BIG
    - *LEFT
    - *SMALL
  x: 1

then

yq '.[4] | explode(.)' sample.yml

will output

r: 10
y: 2
x: 1

Exploding inline merge anchor

Set --yaml-fix-merge-anchor-to-spec=true to get this correct merge behaviour (flag will default to true in late 2025).

Given a sample.yml file of:

a:
  b: &b 42
!!merge <<:
  c: *b

then

yq 'explode(.) | sort_keys(.)' sample.yml

will output

a:
  b: 42
c: 42

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