Examples
RoleResolverPlugin Scenario
Use a resolve scenario to show why some extension points must produce exactly one final answer
RoleResolverPlugin Scenario
Scenario
You want one runtime path to ask:
- "what is this user's current role?"
That is not a collaborative transformation problem. It is a single-answer resolution problem.
That makes it a classic resolve case.
Example
import {
Plugin,
type PluginResolveHook,
} from "@downcity/city/plugin";
class RoleResolverPlugin extends Plugin {
readonly name = "role_resolver";
readonly title = "Role Resolver";
readonly description = "Resolves one final role for a user.";
private readonly resolveRole: PluginResolveHook = async ({ value }) => {
const body = value as { userId?: unknown };
const userId = String(body.userId || "").trim();
if (!userId) {
throw new Error("userId is required");
}
if (userId === "owner") return "admin";
return "member";
};
readonly resolves = {
"auth.resolve_role": this.resolveRole,
};
}
// City has registered role_resolver and bound it to entry's Agent/Workspace.
const role = await city.plugins.scope({ agent_id: agent.id, workspace_id: workspace.id }).resolve<{ userId: string }, string>(
"auth.resolve_role",
{ userId: "owner" },
);Why there cannot be two resolvers
Because the semantic question is not:
- "let several plugins each add something"
It is:
- "who is the final authority for this answer?"
That is why duplicate resolve registration fails in the current implementation.