a3s-flow 1.1.0

Durable workflow engine and Rust SDK for A3S
Documentation 
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use std::sync::Arc;

use a3s_flow::{
    ChildWorkflowCancellationPolicy, FlowEngine, FlowError, FlowEvent, FlowEventStore, FlowRuntime,
    InMemoryEventStore, RuntimeCommand, StepInvocation, WorkflowInvocation, WorkflowSpec,
    WorkflowTerminalOutcome,
};
use async_trait::async_trait;
use serde_json::{json, Value};

fn spec() -> WorkflowSpec {
    WorkflowSpec::rust_embedded(
        "child-validation",
        "1",
        "tests::child_workflow_validation",
        "main",
    )
}

async fn create_started(store: &InMemoryEventStore, run_id: &str) {
    store
        .append(
            run_id,
            FlowEvent::RunCreated {
                spec: spec(),
                input: json!({}),
            },
        )
        .await
        .unwrap();
    store.append(run_id, FlowEvent::RunStarted).await.unwrap();
}

fn request(child_id: &str, child_run_id: &str, input: Value) -> FlowEvent {
    FlowEvent::ChildWorkflowRequested {
        child_id: child_id.into(),
        child_run_id: child_run_id.into(),
        spec: spec(),
        input,
        cancellation_policy: ChildWorkflowCancellationPolicy::RequestCancellation,
    }
}

struct CompleteRuntime;

#[async_trait]
impl FlowRuntime for CompleteRuntime {
    async fn run_workflow(
        &self,
        invocation: WorkflowInvocation,
    ) -> a3s_flow::Result<RuntimeCommand> {
        Ok(invocation.context().complete(json!({})))
    }

    async fn run_step(&self, _invocation: StepInvocation) -> a3s_flow::Result<Value> {
        unreachable!("validation tests do not execute steps")
    }
}

#[tokio::test]
async fn projection_rejects_parent_completion_with_a_blocking_child() {
    let store = Arc::new(InMemoryEventStore::new());
    create_started(&store, "blocking-parent").await;
    store
        .append(
            "blocking-parent",
            request("child", "blocking-child", json!({})),
        )
        .await
        .unwrap();
    store
        .append(
            "blocking-parent",
            FlowEvent::RunCompleted { output: json!({}) },
        )
        .await
        .unwrap();

    let engine = FlowEngine::new(store, Arc::new(CompleteRuntime));
    assert!(matches!(
        engine.snapshot("blocking-parent").await,
        Err(FlowError::InvalidTransition(message))
            if message.contains("cannot terminate while child workflow child is open")
    ));
}

#[tokio::test]
async fn projection_rejects_unknown_duplicate_and_intermediate_child_resolutions() {
    let store = Arc::new(InMemoryEventStore::new());
    create_started(&store, "unknown-resolution").await;
    store
        .append(
            "unknown-resolution",
            FlowEvent::ChildWorkflowResolved {
                child_id: "missing".into(),
                outcome: WorkflowTerminalOutcome::Completed { output: json!({}) },
            },
        )
        .await
        .unwrap();
    let engine = FlowEngine::new(store.clone(), Arc::new(CompleteRuntime));
    assert!(matches!(
        engine.snapshot("unknown-resolution").await,
        Err(FlowError::InvalidTransition(message)) if message.contains("unknown child missing")
    ));

    create_started(&store, "continued-resolution").await;
    store
        .append(
            "continued-resolution",
            request("child", "continued-child", json!({})),
        )
        .await
        .unwrap();
    store
        .append(
            "continued-resolution",
            FlowEvent::ChildWorkflowResolved {
                child_id: "child".into(),
                outcome: WorkflowTerminalOutcome::ContinuedAsNew {
                    successor_run_id: "continued-leaf".into(),
                },
            },
        )
        .await
        .unwrap();
    assert!(matches!(
        engine.snapshot("continued-resolution").await,
        Err(FlowError::InvalidTransition(message))
            if message.contains("cannot resolve to a continuation segment")
    ));
}

struct DriftedReplayRuntime;

#[async_trait]
impl FlowRuntime for DriftedReplayRuntime {
    async fn run_workflow(
        &self,
        invocation: WorkflowInvocation,
    ) -> a3s_flow::Result<RuntimeCommand> {
        Ok(invocation
            .context()
            .start_child_workflow("child", spec(), json!({ "value": 99 })))
    }

    async fn run_step(&self, _invocation: StepInvocation) -> a3s_flow::Result<Value> {
        unreachable!("validation tests do not execute steps")
    }
}

#[tokio::test]
async fn resolved_child_command_drift_is_reported_as_non_determinism() {
    let store = Arc::new(InMemoryEventStore::new());
    create_started(&store, "drift-parent").await;
    store
        .append(
            "drift-parent",
            request("child", "drift-child", json!({ "value": 1 })),
        )
        .await
        .unwrap();
    store
        .append(
            "drift-parent",
            FlowEvent::ChildWorkflowResolved {
                child_id: "child".into(),
                outcome: WorkflowTerminalOutcome::Completed { output: json!({}) },
            },
        )
        .await
        .unwrap();

    let engine = FlowEngine::new(store, Arc::new(DriftedReplayRuntime));
    assert!(matches!(
        engine.drive("drift-parent").await,
        Err(FlowError::NonDeterministic { reason, .. })
            if reason.contains("child workflow child differs")
    ));
}