unique

unique is a DTL operation that deduplicates a sequence while keeping the first occurrence.

Use it after appends or extraction passes that may repeat values.

YOp

- unique:
    path: tags

Parameters

Parameter	Type	Required	Description
path	string	yes	Path to the sequence to deduplicate.
by	string	no	Key to deduplicate by when the sequence contains mappings. Omit for full-value equality.

Behavior

• Requires the target path to exist.
• Requires the target to be a sequence.
• Keeps the first occurrence and removes later duplicates.
• If by is provided, every item must be a mapping containing that key.
• Equality uses canonical encoding, so mapping key order does not affect equality.

Errors

Error	Meaning
PATH_NOT_FOUND	Target path does not exist.
NOT_A_SEQUENCE	Target is not a sequence.
INVALID_OP	by was provided but an item is not a mapping or lacks that key.

Example

yops:
  - unique:
      path: tags

Input:

tags:
  - a
  - b
  - a
  - c
  - b

Output:

tags:
  - a
  - b
  - c