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Sarj Sarj Sarj Standards

prefer-str-enum

Prefer StrEnum for application-owned string domains with explicit closed-set evidence.

SARJ006 Rule source Tests Catalog JSON

Why

A named closed domain lets type checking and review catch invalid values and incomplete handling.

Fix

Define a StrEnum, or a named Literal alias when enum runtime behavior is unnecessary.

Examples

Before — flagged Dispatch rejects every unlisted string
app/render.py
def render(kind: str) -> str:
    match kind:
        case "text":
            return "Text"
        case "image":
            return "Image"
        case _:
            raise ValueError("unsupported kind")
After — preferred Dispatch forwards unlisted strings
app/render.py
def render(kind: str) -> str:
    if kind == "text":
        return "Text"
    if kind == "image":
        return "Image"
    return render_plugin(kind)
Before — flagged String field backed by a closed choice collection
app/order.py
class Order:
    statuses = ("pending", "shipped")
    status: str = "pending"
After — preferred Closed domain represented by a string enum
app/order.py
from enum import StrEnum




class Status(StrEnum):
    PENDING = "pending"
    SHIPPED = "shipped"




class Order:
    status: Status = Status.PENDING