ironflow_engine/context/steps/sub_workflow.rs
1//! Sub-workflow step for [`WorkflowContext`].
2//!
3//! A sub-workflow runs a registered [`WorkflowHandler`] in its own child run.
4//! The child context is built here from the parent's private fields, which is
5//! possible because this module is a descendant of `context`.
6//!
7//! A child that suspends (approval, human input, delay, signal) keeps its own
8//! suspension status and the parent's `Workflow` step stays open with the
9//! child run id in its output. The whole chain is suspended with it; when the
10//! root run replays, the open step re-enters the same child run.
11//!
12//! With `allow_failure` (see [`WorkflowContext::workflow_with`]) a child whose
13//! handler fails is still marked failed, but the parent's step completes with
14//! the failure in its [`SubWorkflowOutput`].
15//!
16//! [`WorkflowContext::workflows_with`] records a wave of `Workflow` steps at
17//! one position and runs their children concurrently (see [`wave`]).
18//!
19//! The child run itself is prepared in [`child`] and executed in
20//! [`child_run`].
21
22mod child;
23mod child_run;
24mod wave;
25
26use chrono::Utc;
27use rust_decimal::Decimal;
28use serde_json::{Value, from_value, json, to_value};
29use tracing::{error, info, warn};
30use uuid::Uuid;
31
32use ironflow_store::models::{
33 NewStep, RunStatus, Step, StepKind, StepStatus, StepUpdate, normalize_worker_tags,
34 step_trace_id,
35};
36
37use crate::config::{WorkflowOptions, WorkflowStepConfig};
38use crate::context::WorkflowContext;
39use crate::context::lifecycle::check_replay_identity;
40use crate::error::EngineError;
41use crate::executor::{
42 ConcurrencyConflict, RecordedWorkflowStep, SubWorkflowOutcome, SubWorkflowOutput,
43};
44use crate::guard::WorkflowRejection;
45use crate::handler::{TypedWorkflow, WorkflowHandler};
46use crate::plan::{SharedPlanRecorder, lock_plan};
47
48/// Key of the open `Workflow` step output that records the child run id.
49const CHILD_RUN_ID_KEY: &str = "child_run_id";
50
51/// The child run id recorded on an open or interrupted `Workflow` step, if any.
52///
53/// A missing or unparsable id means the parent stopped before the child run
54/// was recorded: a new child run is started.
55pub(crate) fn recorded_child_run_id(step: &Step) -> Option<Uuid> {
56 let raw = step.output.as_ref()?.get(CHILD_RUN_ID_KEY)?.as_str()?;
57 match Uuid::parse_str(raw) {
58 Ok(id) => Some(id),
59 Err(err) => {
60 warn!(
61 step_id = %step.id,
62 value = %raw,
63 error = %err,
64 "open workflow step records an invalid child run id"
65 );
66 None
67 }
68 }
69}
70
71/// How a `Workflow` step reaches a child run it already started.
72#[derive(Clone, Copy)]
73enum ChildResume {
74 /// The step was left open by a child that suspended.
75 Suspended(Uuid),
76 /// The step was interrupted by a lost worker lease: the child run may
77 /// still hold the steps that were running in the dead worker.
78 Interrupted(Uuid),
79}
80
81impl ChildResume {
82 /// The child run to re-enter.
83 fn run_id(self) -> Uuid {
84 match self {
85 Self::Suspended(id) | Self::Interrupted(id) => id,
86 }
87 }
88}
89
90/// How a child workflow execution ended, short of a suspension or an error.
91enum ChildOutcome {
92 /// The child run finished; the flag tells whether at least one
93 /// `allow_failure` step failed.
94 Finished(SubWorkflowOutput, bool),
95 /// No child run was created: another active run holds the concurrency key.
96 Conflict(ConcurrencyConflict),
97}
98
99/// Whether `err` stops the parent without closing the child's step: the next
100/// replay re-enters the same child run.
101fn leaves_step_open(err: &EngineError) -> bool {
102 err.is_suspension() || matches!(err, EngineError::RunPaused { .. })
103}
104
105/// The output of a `workflow` or `workflow_dyn` step, which records no
106/// concurrency key and so can only complete.
107///
108/// A conflict is only met on replay, when the step was recorded by
109/// `workflow_with` before the handler code changed.
110fn expect_completed(
111 outcome: SubWorkflowOutcome,
112 position: u32,
113) -> Result<SubWorkflowOutput, EngineError> {
114 match outcome {
115 SubWorkflowOutcome::Completed(output) => Ok(output),
116 SubWorkflowOutcome::Conflict(_) => Err(EngineError::StepConfig(format!(
117 "workflow step at position {position} recorded a concurrency conflict; \
118 call workflow_with to read it"
119 ))),
120 }
121}
122
123impl WorkflowContext {
124 /// Execute a sub-workflow step.
125 ///
126 /// Creates a child run of `handler` whose payload is `input`, executes it
127 /// with its own steps and lifecycle, and returns its run ID and aggregated
128 /// metrics. The child declares its input type through [`TypedWorkflow`],
129 /// so only a `W::Input` is accepted.
130 ///
131 /// When the child suspends (approval, human input, delay or signal), the
132 /// parent is suspended with it and this step stays open. Resuming the
133 /// child resumes the whole chain: the parent replays and re-enters the
134 /// same child run, whose completed steps are replayed.
135 ///
136 /// To tolerate a failed child, see [`workflow_with`](Self::workflow_with).
137 ///
138 /// Requires the context to be created with
139 /// `with_handler_resolver`.
140 ///
141 /// # Errors
142 ///
143 /// Returns [`EngineError::InvalidWorkflow`] if no handler is registered
144 /// with the given name, or if no handler resolver is available, and
145 /// [`EngineError::Serialization`] if `input` cannot be serialized. Returns
146 /// [`EngineError::ReplayDivergence`] when the step recorded at this
147 /// position has a different name or kind, and
148 /// [`EngineError::ChildSuspended`] when the child run suspended.
149 ///
150 /// # Examples
151 ///
152 /// ```no_run
153 /// use ironflow_engine::context::WorkflowContext;
154 /// use ironflow_engine::error::EngineError;
155 /// use ironflow_engine::handler::{HandlerFuture, TypedWorkflow, WorkflowHandler};
156 /// use serde::{Deserialize, Serialize};
157 ///
158 /// #[derive(Serialize, Deserialize)]
159 /// struct CollectInput {
160 /// scope: String,
161 /// }
162 ///
163 /// struct Collect;
164 ///
165 /// impl WorkflowHandler for Collect {
166 /// fn name(&self) -> &str { "collect" }
167 /// fn execute<'a>(&'a self, _ctx: &'a mut WorkflowContext) -> HandlerFuture<'a> {
168 /// Box::pin(async move { Ok(()) })
169 /// }
170 /// }
171 ///
172 /// impl TypedWorkflow for Collect {
173 /// type Input = CollectInput;
174 /// }
175 ///
176 /// # async fn example(ctx: &mut WorkflowContext) -> Result<(), EngineError> {
177 /// let child = ctx.workflow(&Collect, CollectInput { scope: "system".to_string() }).await?;
178 /// let steps = ctx.store()?.list_steps(child.run_id()).await?;
179 /// # Ok(())
180 /// # }
181 /// ```
182 ///
183 /// Any other input type is a compile error:
184 ///
185 /// ```compile_fail,E0308
186 /// # use ironflow_engine::context::WorkflowContext;
187 /// # use ironflow_engine::error::EngineError;
188 /// # use ironflow_engine::handler::{HandlerFuture, TypedWorkflow, WorkflowHandler};
189 /// # #[derive(serde::Serialize, serde::Deserialize)]
190 /// # struct CollectInput { scope: String }
191 /// # struct Collect;
192 /// # impl WorkflowHandler for Collect {
193 /// # fn name(&self) -> &str { "collect" }
194 /// # fn execute<'a>(&'a self, _ctx: &'a mut WorkflowContext) -> HandlerFuture<'a> {
195 /// # Box::pin(async move { Ok(()) })
196 /// # }
197 /// # }
198 /// # impl TypedWorkflow for Collect { type Input = CollectInput; }
199 /// # async fn example(ctx: &mut WorkflowContext) -> Result<(), EngineError> {
200 /// ctx.workflow(&Collect, serde_json::json!({"scope": "system"})).await?;
201 /// # Ok(())
202 /// # }
203 /// ```
204 pub async fn workflow<W: TypedWorkflow>(
205 &mut self,
206 handler: &W,
207 input: W::Input,
208 ) -> Result<SubWorkflowOutput, EngineError> {
209 let payload = to_value(&input)?;
210 let position = self.position;
211 let outcome = self
212 .run_sub_workflow(handler, payload, WorkflowOptions::default())
213 .await?;
214 expect_completed(outcome, position)
215 }
216
217 /// Execute a sub-workflow step with [`WorkflowOptions`].
218 ///
219 /// Same as [`workflow`](Self::workflow), plus a concurrency key set with
220 /// [`WorkflowOptions::concurrency_key`]: the key is held by the child run
221 /// until it reaches a terminal state (Completed, Failed, Warning,
222 /// Cancelled). While another non-terminal run holds it, no child run is
223 /// created and the step completes at once with
224 /// [`SubWorkflowOutcome::Conflict`], naming the run in place. A conflict
225 /// never fails the parent, and it is replayed as-is on resume: the child
226 /// is not attempted again.
227 ///
228 /// A parent that itself holds the key gets a conflict naming its own run.
229 ///
230 /// With [`allow_failure`](WorkflowOptions::allow_failure), a child whose
231 /// handler fails does not fail the parent: the child run is still marked
232 /// failed, but this step completes with a
233 /// [`SubWorkflowOutcome::Completed`] whose [`SubWorkflowOutput`] has a
234 /// [`status`](SubWorkflowOutput::status) of `Failed` (or `Cancelled` when a
235 /// guardrail stopped it) and an [`error`](SubWorkflowOutput::error)
236 /// carrying the child error. The parent run then ends as `Warning`. A
237 /// resumed parent replays the completed step and creates no new child.
238 ///
239 /// A suspension is never tolerated: a child that suspends suspends the
240 /// parent. Errors raised outside the child (no resolver, unknown handler,
241 /// store errors, replay divergence, guard rejection of the invocation) are
242 /// not tolerated either.
243 ///
244 /// # Errors
245 ///
246 /// Same as [`workflow`](Self::workflow), except that the failure of the
247 /// child handler is returned in the output when `allow_failure` is set. A
248 /// conflict raised while creating the child is data, not an error.
249 ///
250 /// # Examples
251 ///
252 /// ```no_run
253 /// use ironflow_engine::config::WorkflowOptions;
254 /// use ironflow_engine::context::WorkflowContext;
255 /// use ironflow_engine::error::EngineError;
256 /// use ironflow_engine::executor::SubWorkflowOutcome;
257 /// use ironflow_engine::handler::{HandlerFuture, TypedWorkflow, WorkflowHandler};
258 /// use serde::{Deserialize, Serialize};
259 ///
260 /// #[derive(Serialize, Deserialize)]
261 /// struct FixInput {
262 /// issue: u64,
263 /// }
264 ///
265 /// struct FixIssue;
266 ///
267 /// impl WorkflowHandler for FixIssue {
268 /// fn name(&self) -> &str { "fix-issue" }
269 /// fn execute<'a>(&'a self, _ctx: &'a mut WorkflowContext) -> HandlerFuture<'a> {
270 /// Box::pin(async move { Ok(()) })
271 /// }
272 /// }
273 ///
274 /// impl TypedWorkflow for FixIssue {
275 /// type Input = FixInput;
276 /// }
277 ///
278 /// # async fn example(ctx: &mut WorkflowContext) -> Result<(), EngineError> {
279 /// let options = WorkflowOptions::new().concurrency_key("issue:12");
280 /// match ctx.workflow_with(&FixIssue, FixInput { issue: 12 }, options).await? {
281 /// SubWorkflowOutcome::Completed(child) => println!("fixed in run {}", child.run_id()),
282 /// SubWorkflowOutcome::Conflict(c) => println!("already handled by run {}", c.run_id()),
283 /// }
284 /// # Ok(())
285 /// # }
286 /// ```
287 pub async fn workflow_with<W: TypedWorkflow>(
288 &mut self,
289 handler: &W,
290 input: W::Input,
291 options: WorkflowOptions,
292 ) -> Result<SubWorkflowOutcome, EngineError> {
293 let payload = to_value(&input)?;
294 self.run_sub_workflow(handler, payload, options).await
295 }
296
297 /// Execute a sub-workflow step whose child is only known at run time.
298 ///
299 /// Same as [`workflow`](Self::workflow), without the compile-time check of
300 /// the payload: the child must deserialize `payload` itself.
301 ///
302 /// # Errors
303 ///
304 /// Same as [`workflow`](Self::workflow).
305 ///
306 /// # Examples
307 ///
308 /// ```no_run
309 /// use ironflow_engine::context::WorkflowContext;
310 /// use ironflow_engine::error::EngineError;
311 /// use ironflow_engine::handler::WorkflowHandler;
312 /// use serde_json::json;
313 ///
314 /// # #[allow(deprecated)]
315 /// # async fn example(ctx: &mut WorkflowContext, child: &dyn WorkflowHandler) -> Result<(), EngineError> {
316 /// let result = ctx.workflow_dyn(child, json!({"scope": "system"})).await?;
317 /// println!("child run {}", result.run_id());
318 /// # Ok(())
319 /// # }
320 /// ```
321 #[deprecated(
322 note = "implement `TypedWorkflow` on the child and call `workflow`: its payload is then checked at compile time"
323 )]
324 pub async fn workflow_dyn(
325 &mut self,
326 handler: &dyn WorkflowHandler,
327 payload: Value,
328 ) -> Result<SubWorkflowOutput, EngineError> {
329 let position = self.position;
330 let outcome = self
331 .run_sub_workflow(handler, payload, WorkflowOptions::default())
332 .await?;
333 expect_completed(outcome, position)
334 }
335
336 /// Record, then run or plan, a sub-workflow step.
337 ///
338 /// A `Workflow` step completed in a previous execution is replayed without
339 /// running the child again. A step left open (`Running`) by a suspended
340 /// child is reused and re-enters the child run it recorded.
341 /// A step interrupted by a lost worker lease is recorded again at the same
342 /// position and re-enters the child run the interrupted step recorded.
343 async fn run_sub_workflow(
344 &mut self,
345 handler: &dyn WorkflowHandler,
346 payload: Value,
347 options: WorkflowOptions,
348 ) -> Result<SubWorkflowOutcome, EngineError> {
349 let (step_name, config) = options.into_step_config(handler.name(), payload);
350
351 // Plan mode: record the invocation, expand the child handler in the
352 // same recorder, and return a synthetic output. No child run is
353 // created and no step of the child is executed.
354 if let Some(plan) = self.plan().cloned() {
355 let planned = self
356 .plan_sub_workflow(&plan, handler, &step_name, config.payload)
357 .await?;
358 return Ok(SubWorkflowOutcome::Completed(planned));
359 }
360
361 let position = self.position;
362
363 let existing = self.replay_steps.get(&position).cloned();
364 if let Some(existing) = &existing {
365 check_replay_identity(existing, position, &step_name, &StepKind::Workflow)?;
366 if existing.status.state == StepStatus::Completed {
367 return self.replay_sub_workflow(existing);
368 }
369 }
370
371 // A step interrupted by a lost lease must be the same step the handler
372 // calls now before its child run is re-entered.
373 let interrupted = self
374 .interrupted_children
375 .get(&(position, step_name.clone()))
376 .cloned();
377 if let Some(interrupted) = &interrupted {
378 check_replay_identity(interrupted, position, &step_name, &StepKind::Workflow)?;
379 }
380
381 // A child runs on the worker that runs its parent: refuse it here
382 // rather than run it on a host missing what it requires.
383 self.check_child_worker_tags(handler)?;
384
385 // Guard: verify the limits and claim the invocation before creating the
386 // step (fail-closed). The claim is atomic, so a sibling of a wave
387 // running its own child at the same time cannot cross the fan-out too.
388 if let (Some(guard_config), Some(guard_state)) = (&self.guard_config, &self.guard_state) {
389 guard_state
390 .lock()
391 .map_err(|_| WorkflowRejection::GuardUnavailable)?
392 .enter(guard_config, handler.name())?;
393 }
394
395 // Paused while it ran: no child is started, the run stops here.
396 if let Err(err) = self.check_not_paused().await {
397 self.guard_record_return();
398 return Err(err);
399 }
400
401 self.position += 1;
402
403 // An open step was left by a child that suspended: reuse it instead of
404 // recording a second step at the same position.
405 let (step_id, resume) = match existing.filter(|s| s.status.state == StepStatus::Running) {
406 Some(step) => (
407 step.id,
408 recorded_child_run_id(&step).map(ChildResume::Suspended),
409 ),
410 None => {
411 let recorded = self
412 .record_workflow_step(&step_name, &config, position)
413 .await;
414 let step_id = match recorded {
415 Ok(step_id) => step_id,
416 Err(err) => {
417 self.guard_record_return();
418 return Err(err);
419 }
420 };
421 // A step interrupted by a lost lease re-enters the child run it
422 // recorded instead of starting a new one.
423 let resume = interrupted
424 .as_ref()
425 .and_then(recorded_child_run_id)
426 .map(ChildResume::Interrupted);
427 (step_id, resume)
428 }
429 };
430
431 let run = self.execute_child_workflow(&config, step_id, resume).await;
432 if matches!(&run.result, Err(err) if err.is_suspension()) {
433 self.sibling_suspensions.extend(run.sibling_suspensions);
434 }
435 let settled = self.settle_child_step(step_id, &config, run.result).await;
436 self.guard_record_return();
437 if settled.is_ok() {
438 self.last_step_ids = vec![step_id];
439 }
440 settled
441 }
442
443 /// Record a `Workflow` step at `position` and start it.
444 async fn record_workflow_step(
445 &self,
446 step_name: &str,
447 config: &WorkflowStepConfig,
448 position: u32,
449 ) -> Result<Uuid, EngineError> {
450 let step = self
451 .store
452 .create_step(NewStep {
453 run_id: self.run_id,
454 trace_id: step_trace_id(self.run_id, step_name, position),
455 name: step_name.to_string(),
456 kind: StepKind::Workflow,
457 position,
458 input: Some(to_value(config)?),
459 is_error_handler: false,
460 })
461 .await?;
462 self.start_step(step.id, Utc::now()).await?;
463 Ok(step.id)
464 }
465
466 /// Close the `Workflow` step `step_id` from what its child produced, and
467 /// account for the child on this run.
468 ///
469 /// A suspended or paused child leaves the step open, neither failed nor
470 /// completed, so the next replay re-enters the same child run.
471 async fn settle_child_step(
472 &mut self,
473 step_id: Uuid,
474 config: &WorkflowStepConfig,
475 result: Result<ChildOutcome, EngineError>,
476 ) -> Result<SubWorkflowOutcome, EngineError> {
477 match result {
478 // No child run was created: the step completes with the conflict
479 // as its output, so a replay serves the same outcome.
480 Ok(ChildOutcome::Conflict(conflict)) => {
481 self.store
482 .update_step(
483 step_id,
484 StepUpdate {
485 status: Some(StepStatus::Completed),
486 output: Some(json!({ "concurrency_conflict": conflict })),
487 duration_ms: Some(0),
488 cost_usd: Some(Decimal::ZERO),
489 completed_at: Some(Utc::now()),
490 ..StepUpdate::default()
491 },
492 )
493 .await?;
494
495 info!(
496 run_id = %self.run_id,
497 child_workflow = %config.workflow_name,
498 key = %conflict.key(),
499 holder = %conflict.run_id(),
500 "workflow step skipped: concurrency conflict"
501 );
502 Ok(SubWorkflowOutcome::Conflict(conflict))
503 }
504 Ok(ChildOutcome::Finished(output, child_had_allowed_failure)) => {
505 // Not `charge_cost`: a child sharing this run's live total
506 // charged its cost there already, step by step.
507 self.total_cost_usd += output.cost_usd();
508 self.total_duration_ms += output.duration_ms();
509 if child_had_allowed_failure {
510 self.has_allowed_failure = true;
511 }
512
513 self.store
514 .update_step(
515 step_id,
516 StepUpdate {
517 status: Some(StepStatus::Completed),
518 output: Some(to_value(&output)?),
519 duration_ms: Some(output.duration_ms()),
520 cost_usd: Some(output.cost_usd()),
521 completed_at: Some(Utc::now()),
522 ..StepUpdate::default()
523 },
524 )
525 .await?;
526
527 info!(
528 run_id = %self.run_id,
529 child_workflow = %config.workflow_name,
530 duration_ms = output.duration_ms(),
531 "workflow step completed"
532 );
533 Ok(SubWorkflowOutcome::Completed(output))
534 }
535 Err(err) if leaves_step_open(&err) => Err(err),
536 Err(err) => {
537 if let Err(store_err) = self
538 .store
539 .update_step(
540 step_id,
541 StepUpdate {
542 status: Some(StepStatus::Failed),
543 error: Some(err.to_string()),
544 completed_at: Some(Utc::now()),
545 ..StepUpdate::default()
546 },
547 )
548 .await
549 {
550 error!(step_id = %step_id, error = %store_err, "failed to persist step failure");
551 }
552 Err(err)
553 }
554 }
555 }
556
557 /// Replay a `Workflow` step completed in a previous execution: the child
558 /// run is not executed again and nothing is re-counted by the guard.
559 ///
560 /// A step skipped on a concurrency conflict replays the same conflict: the
561 /// child is not attempted again, even if the key has been released since.
562 fn replay_sub_workflow(&mut self, step: &Step) -> Result<SubWorkflowOutcome, EngineError> {
563 let outcome = self.replay_recorded_child(step)?;
564 self.position += 1;
565 self.last_step_ids = vec![step.id];
566 Ok(outcome)
567 }
568
569 /// The outcome recorded on a completed `Workflow` step, accounted for on
570 /// this run like the first time, without moving the position.
571 fn replay_recorded_child(&mut self, step: &Step) -> Result<SubWorkflowOutcome, EngineError> {
572 let recorded = step.output.clone().ok_or_else(|| {
573 EngineError::StepConfig(format!(
574 "completed workflow step {} has no recorded output",
575 step.id
576 ))
577 })?;
578 let recorded: RecordedWorkflowStep = from_value(recorded)?;
579
580 let output = match SubWorkflowOutcome::from(recorded) {
581 SubWorkflowOutcome::Completed(output) => output,
582 SubWorkflowOutcome::Conflict(conflict) => {
583 info!(
584 run_id = %self.run_id,
585 step = %step.name,
586 key = %conflict.key(),
587 holder = %conflict.run_id(),
588 "workflow step replayed: concurrency conflict"
589 );
590 return Ok(SubWorkflowOutcome::Conflict(conflict));
591 }
592 };
593
594 // Cost is not added: `carry_over_run_totals` seeded `total_cost_usd`
595 // from the run totals persisted before the suspension, which already
596 // include this child.
597 self.total_duration_ms += output.duration_ms();
598 if matches!(
599 output.status(),
600 RunStatus::Warning | RunStatus::Failed | RunStatus::Cancelled
601 ) {
602 self.has_allowed_failure = true;
603 }
604
605 info!(
606 run_id = %self.run_id,
607 child_run_id = %output.run_id(),
608 step = %step.name,
609 "workflow step replayed from previous execution"
610 );
611 Ok(SubWorkflowOutcome::Completed(output))
612 }
613
614 /// Refuse a child whose required worker tags are not all carried by the
615 /// worker running this context.
616 ///
617 /// No check is made outside a tagged worker (API or local mode).
618 fn check_child_worker_tags(&self, handler: &dyn WorkflowHandler) -> Result<(), EngineError> {
619 let Some(carried) = &self.worker_tags else {
620 return Ok(());
621 };
622 let missing: Vec<String> = normalize_worker_tags(handler.required_worker_tags())
623 .into_iter()
624 .filter(|tag| !carried.contains(tag))
625 .collect();
626 if missing.is_empty() {
627 return Ok(());
628 }
629 Err(EngineError::InvalidWorkflow(format!(
630 "sub-workflow '{}' requires worker tags [{}] that this worker does not carry",
631 handler.name(),
632 missing.join(", ")
633 )))
634 }
635
636 /// Record a sub-workflow invocation while planning, expanding the child
637 /// handler into the same plan when the depth limit allows it.
638 ///
639 /// The child plans against its own payload and under its own workflow
640 /// name; the parent's payload is restored on the way out.
641 async fn plan_sub_workflow(
642 &mut self,
643 plan: &SharedPlanRecorder,
644 handler: &dyn WorkflowHandler,
645 step_name: &str,
646 payload: Value,
647 ) -> Result<SubWorkflowOutput, EngineError> {
648 self.position += 1;
649 {
650 let mut recorder = lock_plan(plan);
651 recorder.record_or_stop(step_name, StepKind::Workflow, &self.workflow_name, None)?;
652 recorder.set_last(vec![step_name.to_string()]);
653 }
654 Ok(self.expand_planned_child(plan, handler, payload).await)
655 }
656
657 /// Expand `handler` into the plan, when the depth limit allows it, and
658 /// return the synthetic output of its step.
659 ///
660 /// The child plans against its own payload and under its own workflow
661 /// name; the parent's payload is restored on the way out.
662 async fn expand_planned_child(
663 &self,
664 plan: &SharedPlanRecorder,
665 handler: &dyn WorkflowHandler,
666 payload: Value,
667 ) -> SubWorkflowOutput {
668 let sub_name = handler.name().to_string();
669 // No child run exists while planning: a nil id and zero metrics.
670 let planned = SubWorkflowOutput::new(
671 Uuid::nil(),
672 &sub_name,
673 RunStatus::Completed,
674 Decimal::ZERO,
675 0,
676 );
677
678 let expand = lock_plan(plan).enter_workflow();
679 if expand {
680 let previous_payload = lock_plan(plan).swap_payload(payload.clone());
681
682 let mut child = WorkflowContext::new(
683 Uuid::now_v7(),
684 sub_name.clone(),
685 self.store.clone(),
686 self.provider.clone(),
687 );
688 child.handler_resolver = self.handler_resolver.clone();
689 child.set_plan(plan.clone());
690
691 if let Err(err) = handler.execute(&mut child).await {
692 lock_plan(plan).fail(format!(
693 "sub-workflow {sub_name} could not be planned: {err}"
694 ));
695 }
696
697 let mut recorder = lock_plan(plan);
698 recorder.swap_payload(previous_payload);
699 recorder.leave_workflow();
700 }
701
702 planned
703 }
704}