aion/workflow/entrypoint

workflow.entrypoint: the engine-facing run adapter, assembled from a WorkflowDefinition’s codecs and typed entry function.

The engine spawns entry_module:entry_function/1 with one argument: a BEAM binary holding the start input’s JSON text. Every workflow used to hand-write the same adapter — decode the binary to a string, decode the string with the input codec, call the typed entry function, encode the output or error back to JSON text. entrypoint is that adapter, built purely from the definition’s own accessors, so a workflow module’s engine entry collapses to one line:

pub fn run(raw_input: Dynamic) -> Result(String, String) {
  workflow.entrypoint(definition(), raw_input)
}

Success and typed failure are byte-identical to the hand-written adapter: Ok encodes with the definition’s output codec, Error with its error codec, so an awaiting parent decodes both with the same codecs it already holds. Only the garbage-input edge has a fixed shape: when the raw payload is not a string or the input codec rejects it, the failure payload is the documented JSON envelope {"aion_error":"input_decode","reason":...,"path":[...]} — the engine records it as failure details, and a parent awaiting the child surfaces it as typed error-decode data, never a crash.

pub fn entrypoint(
  definition: define.WorkflowDefinition(
    input,
    output,
    workflow_error,
  ),
  raw_input: dynamic.Dynamic,
) -> Result(String, String)