Create LaunchDarkly adapter

.changeset/kind-carpets-unite.md

@@ -0,0 +1,5 @@
+---
+'@flags-sdk/launchdarkly': minor
+---
+
+Add LaunchDarkly adapter

.github/workflows/release-snapshot.yaml

@@ -84,9 +84,10 @@ jobs:
           EDGE_CONFIG: ${{ secrets.EDGE_CONFIG }}
           FLAGS_SECRET: ${{ secrets.FLAGS_SECRET }}
           FLAGS: ${{ secrets.FLAGS }}
-          LAUNCHDARKLY_API_TOKEN: ${{ secrets.LAUNCHDARKLY_API_TOKEN }}
           HAPPYKIT_API_TOKEN: ${{ secrets.HAPPYKIT_API_TOKEN }}
           HAPPYKIT_ENV_KEY: ${{ secrets.HAPPYKIT_ENV_KEY }}
+          LAUNCHDARKLY_CLIENT_SIDE_ID: ${{ secrets.LAUNCHDARKLY_CLIENT_SIDE_ID }}
+          LAUNCHDARKLY_PROJECT_SLUG: ${{ secrets.LAUNCHDARKLY_PROJECT_SLUG }}
 
       - name: Publish Snapshot Release
         run: pnpm changeset publish --no-git-tag --tag snapshot

.github/workflows/release.yml

@@ -42,6 +42,7 @@ jobs:
           NPM_TOKEN: ${{ secrets.NPM_TOKEN_ELEVATED }}
           EDGE_CONFIG: ${{ secrets.EDGE_CONFIG }}
           FLAGS_SECRET: ${{ secrets.FLAGS_SECRET }}
-          LAUNCHDARKLY_API_TOKEN: ${{ secrets.LAUNCHDARKLY_API_TOKEN }}
           HAPPYKIT_API_TOKEN: ${{ secrets.HAPPYKIT_API_TOKEN }}
           HAPPYKIT_ENV_KEY: ${{ secrets.HAPPYKIT_ENV_KEY }}
+          LAUNCHDARKLY_CLIENT_SIDE_ID: ${{ secrets.LAUNCHDARKLY_CLIENT_SIDE_ID }}
+          LAUNCHDARKLY_PROJECT_SLUG: ${{ secrets.LAUNCHDARKLY_PROJECT_SLUG }}

examples/shirt-shop/package.json

@@ -25,7 +25,7 @@
     "framer-motion": "12.4.7",
     "js-xxhash": "4.0.0",
     "nanoid": "5.1.2",
-    "next": "15.2.1-canary.4",
+    "next": "15.2.2-canary.4",
     "react": "^19.0.0",
     "react-dom": "^19.0.0",
     "sonner": "2.0.1"

examples/snippets/package.json

@@ -9,6 +9,8 @@
     "start": "next start"
   },
   "dependencies": {
+    "@flags-sdk/launchdarkly": "workspace:*",
+    "@launchdarkly/vercel-server-sdk": "1.3.21",
     "@radix-ui/react-dialog": "1.1.2",
     "@radix-ui/react-separator": "1.1.0",
     "@radix-ui/react-slot": "1.1.0",
@@ -19,7 +21,7 @@
     "clsx": "2.0.0",
     "flags": "workspace:*",
     "nanoid": "5.0.7",
-    "next": "15.2.1-canary.2",
+    "next": "15.2.2-canary.4",
     "next-themes": "0.4.4",
     "react": "19.0.0-rc.1",
     "react-dom": "19.0.0-rc.1",

packages/adapter-launchdarkly/README.md

@@ -0,0 +1,67 @@
+# Flags SDK - LaunchDarkly Provider
+
+The [LaunchDarkly provider](https://flags-sdk.dev/docs/api-reference/adapters/launchdarkly) for the [Flags SDK](https://flags-sdk.dev/) contains support for LaunchDarkly's Feature Flags.
+
+## Setup
+
+The Statsig provider is available in the `@flags-sdk/statsig` module. You can install it with
+
+```bash
+npm i @flags-sdk/launchdarkly
+```
+
+## Provider Instance
+
+**NOTE:** The [LaunchDarkly Vercel integration](https://vercel.com/integrations/launchdarkly) must be installed on your account, as this adapter loads LaunchDarkly from Edge Config. The adapter can not be used without Edge Config.
+
+Import the default adapter instance `launchDarkly` from `@flags-sdk/launchdarkly`:
+
+```ts
+import { launchDarkly } from '@flags-sdk/launchdarkly';
+```
+
+The default adapter uses the following environment variables to configure itself:
+
+```sh
+export LAUNCHDARKLY_CLIENT_SIDE_ID="612376f91b8f5713a58777a1"
+export LAUNCHDARKLY_PROJECT_SLUG="my-project"
+# Provided by Vercel when connecting an Edge Config to the project
+export EDGE_CONFIG="https://edge-config.vercel.com/ecfg_abdc1234?token=xxx-xxx-xxx"
+```
+
+## Example
+
+```ts
+import { flag, dedupe } from 'flags/next';
+import { launchDarkly, type LDContext } from '@flags-sdk/launchdarkly';
+
+const identify = dedupe(async (): Promise<LDContext> => {
+  return {
+    key: 'user_123',
+  };
+});
+
+export const showBanner = flag<boolean, LDContext>({
+  key: 'show-banner',
+  identify,
+  adapter: launchDarkly(),
+});
+```
+
+## Custom Adapter
+
+Create an adapter by using the `createLaunchDarklyAdapter` function:
+
+```ts
+import { createLaunchDarklyAdapter } from '@flags-sdk/launchdarkly';
+
+const adapter = createLaunchDarklyAdapter({
+  projectSlug: 'my-project',
+  ldClientSideKey: '612376f91b8f5713a58777a1',
+  edgeConfigConnectionString: process.env.EDGE_CONFIG,
+});
+```
+
+## Documentation
+
+Please check out the [LaunchDarkly provider documentation](https://flags-sdk.dev/docs/api-reference/adapters/launchdarkly) for more information.

packages/adapter-launchdarkly/package.json

@@ -35,7 +35,10 @@
     "test:watch": "vitest",
     "type-check": "tsc --noEmit"
   },
-  "dependencies": {},
+  "dependencies": {
+    "@launchdarkly/vercel-server-sdk": "^1.3.23",
+    "@vercel/edge-config": "^1.4.0"
+  },
   "devDependencies": {
     "@types/node": "20.11.17",
     "eslint-config-custom": "workspace:*",
@@ -48,7 +51,6 @@
     "vite": "5.1.1",
     "vitest": "1.4.0"
   },
-  "peerDependencies": {},
   "publishConfig": {
     "access": "public"
   }

packages/adapter-launchdarkly/src/index.ts

@@ -1 +1,79 @@
+import type { Adapter } from 'flags';
+import { createClient } from '@vercel/edge-config';
+import {
+  init,
+  LDClient,
+  type LDContext,
+} from '@launchdarkly/vercel-server-sdk';
+
 export { getProviderData } from './provider';
+export type { LDContext };
+
+interface AdapterOptions<ValueType> {
+  defaultValue?: ValueType;
+}
+
+let defaultLaunchDarklyAdapter:
+  | ReturnType<typeof createLaunchDarklyAdapter>
+  | undefined;
+
+function assertEnv(name: string): string {
+  const value = process.env[name];
+  if (!value) {
+    throw new Error(
+      `LaunchDarkly Adapter: Missing ${name} environment variable`,
+    );
+  }
+  return value;
+}
+
+export function createLaunchDarklyAdapter({
+  projectSlug,
+  clientSideId,
+  edgeConfigConnectionString,
+}: {
+  projectSlug: string;
+  clientSideId: string;
+  edgeConfigConnectionString: string;
+}) {
+  const edgeConfigClient = createClient(edgeConfigConnectionString);
+  const ldClient = init(clientSideId, edgeConfigClient);
+
+  return function launchDarklyAdapter<ValueType>(
+    options: AdapterOptions<ValueType> = {},
+  ): Adapter<ValueType, LDContext> & { ldClient: LDClient } {
+    return {
+      /** The LaunchDarkly client instance used by the adapter. */
+      ldClient,
+      origin(key) {
+        return `https://app.launchdarkly.com/projects/${projectSlug}/flags/${key}/`;
+      },
+      async decide({ key, entities }): Promise<ValueType> {
+        await ldClient.waitForInitialization();
+        return ldClient.variation(
+          key,
+          entities as LDContext,
+          options.defaultValue,
+        ) as ValueType;
+      },
+    };
+  };
+}
+
+export function launchDarkly<ValueType>(
+  options?: AdapterOptions<ValueType>,
+): Adapter<ValueType, LDContext> {
+  if (!defaultLaunchDarklyAdapter) {
+    const edgeConfigConnectionString = assertEnv('EDGE_CONFIG');
+    const clientSideId = assertEnv('LAUNCHDARKLY_CLIENT_SIDE_ID');
+    const projectSlug = assertEnv('LAUNCHDARKLY_PROJECT_SLUG');
+
+    defaultLaunchDarklyAdapter = createLaunchDarklyAdapter({
+      projectSlug,
+      clientSideId,
+      edgeConfigConnectionString,
+    });
+  }
+
+  return defaultLaunchDarklyAdapter(options);
+}

packages/flags/src/types.ts

@@ -150,6 +150,7 @@ export interface Adapter<ValueType, EntitiesType> {
     entities?: EntitiesType;
     headers: ReadonlyHeaders;
     cookies: ReadonlyRequestCookies;
+    defaultValue?: ValueType;
   }) => Promise<ValueType> | ValueType;
 }