Add typed createIdentify

Author: mikechabot

src/identify.ts

@@ -0,0 +1,13 @@
+import { FsUserContext } from '@flagsync/node-sdk';
+import { Identify } from '@vercel/flags';
+
+type ExtractParams<T> = T extends (params: infer P) => any ? P : never;
+
+export const createIdentify =
+  (
+    callback: (
+      params: ExtractParams<Identify<FsUserContext>>,
+    ) => Promise<FsUserContext> | FsUserContext,
+  ): Identify<FsUserContext> =>
+  (params) =>
+    callback(params);

src/index.ts

@@ -19,3 +19,5 @@ export {
   createJsonFlagAdaptor,
   createNumberFlagAdaptor,
 } from './adapter';
+
+export { createIdentify } from './identify';

src/types.ts

@@ -1,6 +1,6 @@
-export type JsonPrimitive = string | number | boolean | null;
-export type JsonValue = JsonPrimitive | JsonObject | JsonArray;
-export interface JsonArray extends Array<JsonValue> {}
-export interface JsonObject {
-  [key: string]: JsonValue;
-}
+export type JsonPrimitive = string | number | boolean | null;
+export type JsonValue = JsonPrimitive | JsonObject | JsonArray;
+export type JsonArray = Array<JsonValue>;
+export interface JsonObject {
+  [key: string]: JsonValue;
+}