Functions

Breyta functions reference for reusable Clojure transforms in :function steps.

Quick Answer

Define transform logic once in :functions and call by stable :ref from flow/step :function to keep orchestration small and deterministic.

functions define reusable Clojure transforms referenced by :function steps.

Declare functions at top level:

{:functions [{:id :summarize
              :language :clojure
              :code "(fn [input] {:count (count (:rows input))})"}]}

Call from flow:

(flow/step :function :summarize-rows
  {:ref :summarize
   :input {:rows rows}})

keep function logic pure and deterministic
use functions for data transformation, not external side effects
use :function steps for non-trivial shaping/normalization, even if used once
keep inline :flow code focused on orchestration (ordering, branching, retries, waits)
keep ids stable; avoid renaming unless intentional
prefer multiline flow files over long one-line string literals

function code is resolved by :ref from the flow definition
when running a function step in isolation via CLI, include --flow <slug> so refs resolve
only allowlisted Java interop is available in the function runtime

unresolved :ref: confirm function id exists and matches exactly
parse/EDN failures: validate file structure and avoid accidental escaped newlines outside strings
runtime errors: run step in isolation first, then run full flow after fix