Split a single file into multiple by map value field

[ESipalis]

Hello,
Having an input value like the following:

FirstValue:
    name: John
    group: FirstGroup
SecondValue:
    name: NotJohn
    group: SecondGroup
ThirdValue:
    name: MaybeJohn
    group: SecondGroup

I'd like to split it into multiple files, where the destination file would depend on the value of <key>.group.
Expected output:

# FirstGroup.yaml
FirstValue:
    name: John
    group: FirstGroup

# SecondGroup.yaml
SecondValue:
    name: NotJohn
    group: SecondGroup
ThirdValue:
    name: MaybeJohn
    group: SecondGroup

I've tried yq ..\yq-input.yaml -s 'to_entries | .[] | .value.group', but it produces only 1 file with all the output.

# FirstGroup.yaml
FirstValue:
    name: John
    group: FirstGroup
SecondValue:
    name: NotJohn
    group: SecondGroup
ThirdValue:
    name: MaybeJohn
    group: SecondGroup

Thanks!

[mikefarah]

Sure:

yq 'to_entries | group_by(.value.group) | (.[] |= from_entries) | .[]' -s '.. | .group + ".yaml"'

Explanation:

• to_entries converts the map into an entries array
• then we can use group_by to group by the entry value group
• Now we have and array with two elements, grouped by group name. Each of which is itself an array of entries
• Convert the nested array elements back into objects (.[] |= from_entries)
• Now we have an array with two elements, each of which is a map
• Splat that array into its components .[]
• Use the -s flag to write a file of each of the splatted components. Use .. | .group as the filename