Generate State Machine Diagrams

The compiler generates Mermaid diagrams from .ddd files. Each diagram type operates on the validated AST — no additional configuration is needed.

What You Get

Each decider produces one stateDiagram-v2 diagram showing states, transitions, and terminal markers.

Example

Given this .ddd decider:

decider User {
    commands: Register, Deactivate
    events: Registered, Deactivated
    state: Unregistered | Active | Inactive
    initial: Unregistered
    terminal: Inactive

    evolve(Unregistered, Registered) -> Active
    evolve(Unregistered, Deactivated) -> Inactive
    evolve(Active, Registered) -> Active
    evolve(Active, Deactivated) -> Inactive
}

The generator produces:

stateDiagram-v2
    [*] --> Unregistered
    Unregistered --> Active : Registered
    Unregistered --> Inactive : Deactivated
    Active --> Active : Registered
    Active --> Inactive : Deactivated
    Inactive --> [*]

Prerequisites

A valid .ddd file with evolve clauses and (optionally) terminal and initial declarations.

Mapping Reference

DSL Source	Mermaid Output
initial: StateName	[*] --> StateName (initial state)
evolve(From, Event) -> To	From --> To : Event
terminal: State	State --> [*]

Self-transitions (evolve(A, E) -> A) produce A --> A : E.

Conventions

• Declaration order preserved: Transitions appear in the same order as evolve clauses in the source .ddd file.
• Initial state: The state declared in initial: is the initial state ([*] -->).
• Terminal states: Only states listed in terminal: produce end markers (--> [*]). States not listed as terminal do not.
• State names: The grammar enforces identifiers matching [_a-zA-Z][\w]*, which is valid Mermaid syntax. No escaping is needed.

Output

Diagram files use the .mmd extension and are written to the configured output directory, never mixed with .ddd source files.