yq/pkg/yqlib/doc/usage/properties.md

Properties

Encode to a property file (decode not yet supported). Line comments on value nodes will be copied across.

By default, empty maps and arrays are not encoded - see below for an example on how to encode a value for these.

Encode properties

Note that empty arrays and maps are not encoded by default.

Given a sample.yml file of:

# block comments don't come through
person: # neither do comments on maps
    name: Mike # comments on values appear
    pets: 
    - cat # comments on array values appear
    food: [pizza] # comments on arrays do not
emptyArray: []
emptyMap: []

then

yq -o=props -I=0 '.' sample.yml

will output

# comments on values appear
person.name = Mike

# comments on array values appear
person.pets.0 = cat
person.food.0 = pizza

Encode properties: no comments

Given a sample.yml file of:

# block comments don't come through
person: # neither do comments on maps
    name: Mike # comments on values appear
    pets: 
    - cat # comments on array values appear
    food: [pizza] # comments on arrays do not
emptyArray: []
emptyMap: []

then

yq -o=props -I=0 '... comments = ""' sample.yml

will output

person.name = Mike
person.pets.0 = cat
person.food.0 = pizza

Encode properties: include empty maps and arrays

Use a yq expression to set the empty maps and sequences to your desired value.

Given a sample.yml file of:

# block comments don't come through
person: # neither do comments on maps
    name: Mike # comments on values appear
    pets: 
    - cat # comments on array values appear
    food: [pizza] # comments on arrays do not
emptyArray: []
emptyMap: []

then

yq -o=props -I=0 '(.. | select( (tag == "!!map" or tag =="!!seq") and length == 0)) = ""' sample.yml

will output

# comments on values appear
person.name = Mike

# comments on array values appear
person.pets.0 = cat
person.food.0 = pizza
emptyArray = 
emptyMap =