# SPDX-License-Identifier: Apache-2.0
# yaml-language-server: $schema=https://nika.sh/spec/v1/workflow.schema.json
#
# 07 · for_each fan-out — one task, many items.
#
# 02 fanned out by writing three tasks. That works until the list is decided
# at run time, or has fifty entries. `for_each:` is the same fan-out with the
# collection as data: one task definition, one iteration per element, and a
# `.output` that is the array of results in input order.
#
# Demonstrates ·
#   - `for_each:` · run a task once per element of a collection
#   - `${{ item }}` + `${{ index }}` · loop-scoped locals, not a namespace
#   - `max_parallel:` · a ceiling on concurrent iterations
#   - `fail_fast: false` · finish the batch even when one element fails
#   - fan-in · the whole array lands in one downstream binding
#
# Run · nika run examples/07-for-each-locales.nika.yaml

nika: v1
workflow:
  id: for-each-locales

model: mock/echo   # the dry twin · this file teaches the loop, not the translations

permits: {}        # pure compute · no file, no host, no program (see 01)

const:
  source: "Welcome to the launch."
  locales: ["fr", "es", "de", "ja", "pt"]

tasks:
  translate:
    for_each: ${{ const.locales }}   # five elements → five iterations
    max_parallel: 3                  # at most 3 in flight · the rest queue
    # Default is fail_fast: true — the first failure cancels the siblings.
    # A batch job usually wants the opposite: four good translations beat
    # zero, and you would rather learn which one broke.
    fail_fast: false
    on_error:
      # Without this, a failed element fails the task even under
      # fail_fast: false. `recover: null` keeps the array whole and puts a
      # null at that index — so filter nulls at the fan-in below.
      recover: null
    with:
      locale: ${{ item }}   # the current element
      n: ${{ index }}       # its 0-based position
    infer:
      prompt: "Translate to locale '${{ with.locale }}' (#${{ with.n }}) · ${{ const.source }}"
      max_tokens: 256

  collect:
    with:
      # One binding, five results. `tasks.translate.output` is the ARRAY, in
      # the order of `const.locales` — not the order they finished.
      translations: ${{ tasks.translate.output }}
    infer:
      prompt: "Combine these translations into a localization table · ${{ with.translations }}"
      max_tokens: 1024

# Both the array and the table, so the ordering guarantee is visible · read
# with `--output json`.
outputs:
  translations: ${{ tasks.translate.output }}
  table: ${{ tasks.collect.output }}

the path · 07

for_each fan-out — one task, many items.

run itnika try 07-for-each-locales

07-for-each-locales.nika.yaml

1# SPDX-License-Identifier: Apache-2.02# yaml-language-server: $schema=https://nika.sh/spec/v1/workflow.schema.json3#4# 07 · for_each fan-out — one task, many items.5#6# 02 fanned out by writing three tasks. That works until the list is decided7# at run time, or has fifty entries. `for_each:` is the same fan-out with the8# collection as data: one task definition, one iteration per element, and a9# `.output` that is the array of results in input order.10#11# Demonstrates ·12#   - `for_each:` · run a task once per element of a collection13#   - `${{ item }}` + `${{ index }}` · loop-scoped locals, not a namespace14#   - `max_parallel:` · a ceiling on concurrent iterations15#   - `fail_fast: false` · finish the batch even when one element fails16#   - fan-in · the whole array lands in one downstream binding17#18# Run · nika run examples/07-for-each-locales.nika.yaml1920nika: v121workflow:22  id: for-each-locales2324model: mock/echo   # the dry twin · this file teaches the loop, not the translations2526⛨permits: {}        # pure compute · no file, no host, no program (see 01)2728const:29  source: "Welcome to the launch."30  locales: ["fr", "es", "de", "ja", "pt"]3132tasks:33  translate:34    for_each: ${{ const.locales }}   # five elements → five iterations35    max_parallel: 3                  # at most 3 in flight · the rest queue36    # Default is fail_fast: true — the first failure cancels the siblings.37    # A batch job usually wants the opposite: four good translations beat38    # zero, and you would rather learn which one broke.39    fail_fast: false40    on_error:41      # Without this, a failed element fails the task even under42      # fail_fast: false. `recover: null` keeps the array whole and puts a43      # null at that index — so filter nulls at the fan-in below.44      recover: null45    with:46      locale: ${{ item }}   # the current element47      n: ${{ index }}       # its 0-based position48    ◇infer:49      prompt: "Translate to locale '${{ with.locale }}' (#${{ with.n }}) · ${{ const.source }}"50      max_tokens: 2565152  collect:53    with:54      # One binding, five results. `tasks.translate.output` is the ARRAY, in55      # the order of `const.locales` — not the order they finished.56      translations: ${{ tasks.translate.output }}57    ◇infer:58      prompt: "Combine these translations into a localization table · ${{ with.translations }}"59      max_tokens: 10246061# Both the array and the table, so the ordering guarantee is visible · read62# with `--output json`.63outputs:64  translations: ${{ tasks.translate.output }}65  table: ${{ tasks.collect.output }}66

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