fix (#339)

Author: dferber90

.changeset/brave-rooms-go.md

@@ -0,0 +1,6 @@
+---
+"@vercel/flags-core": patch
+"@flags-sdk/vercel": patch
+---
+
+Loosen the type restrictions on the `Evaluation` type as the previous implementation would only work with `interface` but not with `type` that lead to an accidental breaking change.

packages/adapter-vercel/src/index.test.ts

@@ -1,5 +1,5 @@
 import { flagsClient, resetDefaultFlagsClient } from '@vercel/flags-core';
-import type { Origin, ProviderData } from 'flags';
+import type { Adapter, Origin, ProviderData } from 'flags';
 import { flag } from 'flags/next';
 import { HttpResponse, http } from 'msw';
 import { setupServer } from 'msw/node';
@@ -10,6 +10,7 @@ import {
   beforeEach,
   describe,
   expect,
+  expectTypeOf,
   it,
   vi,
 } from 'vitest';
@@ -102,6 +103,20 @@ describe('createVercelAdapter', () => {
       sdkKey: 'vf_my_sdk_key',
     } satisfies Origin);
   });
+
+  it('has correct types', () => {
+    const adapter = createVercelAdapter(flagsClient);
+    type SampleValue = boolean;
+    type SampleEvaluationContext = { user: { id: string } };
+    const instance = adapter<SampleValue, SampleEvaluationContext>();
+    expectTypeOf(instance).toEqualTypeOf<
+      Adapter<SampleValue, SampleEvaluationContext>
+    >();
+    expectTypeOf(instance.decide)
+      .parameter(0)
+      .toHaveProperty('entities')
+      .toEqualTypeOf<SampleEvaluationContext | undefined>();
+  });
 });
 
 describe('when used with getProviderData', () => {

packages/adapter-vercel/src/index.ts

@@ -30,10 +30,10 @@ export function createVercelAdapter(
       ? createClient(sdkKeyOrFlagsClient)
       : sdkKeyOrFlagsClient;
 
-  return function vercelAdapter<
+  return function vercelAdapter<ValueType, EntitiesType>(): Adapter<
     ValueType,
-    EntitiesType extends Record<string, unknown>,
-  >(): Adapter<ValueType, EntitiesType> {
+    EntitiesType
+  > {
     return {
       origin: flagsClient.origin,
       config: { reportValue: false },
@@ -75,10 +75,10 @@ export function resetDefaultVercelAdapter() {
  *
  */
 // This is initialized lazily to avoid warning when it is not actually used and env vars are missing.
-export function vercelAdapter<
+export function vercelAdapter<ValueType, EntitiesType>(): Adapter<
   ValueType,
-  EntitiesType extends Record<string, unknown>,
->(): Adapter<ValueType, EntitiesType> {
+  EntitiesType
+> {
   if (!defaultVercelAdapter) {
     defaultVercelAdapter = createVercelAdapter(flagsClient);
   }

packages/vercel-flags-core/src/types.ts

@@ -1,5 +1,3 @@
-import type { ControllerInstance } from './controller-fns';
-
 /**
  * Options for stream connection behavior
  */
@@ -138,7 +136,7 @@ export type FlagsClient<Entities = Record<string, unknown>> = {
    * @param entities
    * @returns
    */
-  evaluate: <T = Value, E extends Entities = Entities>(
+  evaluate: <T = Value, E = Entities>(
     flagKey: string,
     defaultValue?: T,
     entities?: E,