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Workflow

State machine helpers live in serenade-workflow (#239).

Symfony Workflow shaped: places, transitions, guards, marking store. No commerce types.

Concepts

Section titled “Concepts”
Piece Role
Definition / DefinitionBuilder Places, transitions, initial marking
Transition Named edge from → to (one or many places each side)
Marking Places currently occupied by a subject
MarkingStore / MemoryMarkingStore Persist markings by subject id
Workflow can / apply / enabled_transitions
Guard Block a transition before it applies (Rust closure or ExpressionGuard)
ExpressionGuard Guard from a boolean expression string (see EXPRESSION.md)
TransitionListener Hook after a successful apply

Example

Section titled “Example”
use std::sync::Arc;
use serenade_workflow::{DefinitionBuilder, MemoryMarkingStore, Workflow};


let definition = DefinitionBuilder::new()
    .places(["draft", "published", "archived"])
    .edge("publish", "draft", "published")
    .edge("archive", "published", "archived")
    .build()?;
let store = Arc::new(MemoryMarkingStore::new());
let workflow = Workflow::new("article", definition, store);


assert!(workflow.can("post-1", "publish"));
workflow.apply("post-1", "publish")?;
assert!(!workflow.can("post-1", "publish"));
assert!(workflow.can("post-1", "archive"));

Guards

Section titled “Guards”

Register per transition name, or "*" for every transition:

use std::sync::Arc;
use serenade_workflow::{Guard, TransitionContext, Workflow, block};


workflow.add_guard(
    "publish",
    Arc::new(|ctx: &TransitionContext<'_>| {
        if ctx.subject_id.starts_with("guest:") {
            Err(block(ctx.transition.name(), "guests cannot publish"))
        } else {
            Ok(())
        }
    }),
);

Or use a rule expression (EXPRESSION.md):

use std::sync::Arc;
use serenade_workflow::ExpressionGuard;


workflow.add_guard(
    "publish",
    Arc::new(ExpressionGuard::new(
        r#"!(subject_id == "guest") && place.draft"#,
    )),
);

Limits

Section titled “Limits”
  • Subject identity is a string id (apps map entities → ids)
  • In-memory store only in this crate; implement [MarkingStore] for DB/Redis
  • No DI compile pass yet (construct Workflow in app code)
Section titled “Related”