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Merged
joker23 merged 1 commit into from
Mar 23, 2026
Merged

chore: adding better bootstrap support for react sdk #1194

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26 changes: 25 additions & 1 deletion packages/sdk/react/__tests__/client/provider/LDReactProvider.test.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,6 @@ jest.mock('../../../src/client/LDReactClient', () => ({
}));

// ─── createLDReactProviderWithClient ────────────────────────────────────────

it('renders children', () => {
const client = makeMockClient();
const Provider = createLDReactProviderWithClient(client);
Expand Down Expand Up @@ -219,6 +218,31 @@ describe('createLDReactProvider (convenience factory)', () => {
expect(mockClient.start).toHaveBeenCalledWith(startOptions);
});

it('merges bootstrap into startOptions when bootstrap is provided', () => {
const bootstrapData = { $flagsState: { flag: { variation: 0 } }, $valid: true };
createLDReactProvider('sdk-key', { kind: 'user', key: 'u1' }, { bootstrap: bootstrapData });

expect(mockClient.start).toHaveBeenCalledWith({ bootstrap: bootstrapData });
});

it('merges bootstrap with existing startOptions', () => {
const bootstrapData = { $flagsState: { flag: { variation: 0 } }, $valid: true };
const startOptions = { timeout: 5 };
createLDReactProvider(
'sdk-key',
{ kind: 'user', key: 'u1' },
{ startOptions, bootstrap: bootstrapData },
);

expect(mockClient.start).toHaveBeenCalledWith({ timeout: 5, bootstrap: bootstrapData });
});

it('does not merge bootstrap into startOptions when bootstrap is not provided', () => {
createLDReactProvider('sdk-key', { kind: 'user', key: 'u1' });

expect(mockClient.start).toHaveBeenCalledWith(undefined);
});

it('uses provided reactContext option', () => {
const CustomContext = initLDReactContext();
const contextValues: LDReactClientContextValue[] = [];
Expand Down
13 changes: 13 additions & 0 deletions packages/sdk/react/src/client/LDOptions.ts
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Expand Up @@ -70,4 +70,17 @@ export interface LDReactProviderOptions {
* @returns {LDReactClientContext} The react context for the LaunchDarkly client.
*/
reactContext?: LDReactClientContext;

/**
* Bootstrap data from the server. Pass the result of `flagsState.toJSON()` obtained
* from the server SDK's `allFlagsState` method.
*
* When provided, the client immediately uses these values before the first network
* response arrives — eliminating the flag-fetch waterfall on page load.
*
* This is merged into `startOptions.bootstrap` when the client is started. If both
* `bootstrap` and `startOptions.bootstrap` are provided, this top-level value takes
* precedence.
*/
bootstrap?: unknown;
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@joker23 joker23 Mar 18, 2026

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This matches https://github.com/launchdarkly/js-core/blob/main/packages/sdk/browser/src/LDClient.ts#L15

}
5 changes: 3 additions & 2 deletions packages/sdk/react/src/client/provider/LDReactProvider.tsx
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Expand Up @@ -120,12 +120,13 @@ export function createLDReactProvider(
context: LDContext,
options?: LDReactProviderOptions,
): React.FC<{ children: React.ReactNode }> {
const { deferInitialization, startOptions, reactContext, ldOptions } = options ?? {};
const { deferInitialization, startOptions, reactContext, ldOptions, bootstrap } = options ?? {};

const client = createClient(clientSideID, context, ldOptions);

if (!deferInitialization) {
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@joker23 joker23 Mar 18, 2026

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I figured if users are deferring start then they will need to provide their own start options. We may need to call this out in docs somewhere.

client.start(startOptions);
const effectiveStartOptions = bootstrap ? { ...startOptions, bootstrap } : startOptions;
client.start(effectiveStartOptions);
}
Comment on lines 127 to 130
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@devin-ai-integration devin-ai-integration bot Mar 18, 2026 •
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🟡 Bootstrap data is silently discarded when deferInitialization: true

When a user passes { bootstrap: myData, deferInitialization: true } to createLDReactProvider, the bootstrap value is destructured from options at line 119 but never used because the if (!deferInitialization) block (lines 123-126) is skipped entirely. Since createLDReactProvider returns a React.FC (not the client), the user has no way to recover the lost bootstrap data. The only way to later call start() is through the useLDClient() hook (packages/sdk/react/src/client/hooks/useLDClient.ts:14), but the bootstrap data from the original options is inaccessible at that point. The API happily accepts this combination without any warning, silently discarding the user's bootstrap data.

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@joker23 joker23 Mar 20, 2026

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I think this is fine as we should have it documented that if developers decide to defer initialization then they are responsible for starting the client however they want.


return createLDReactProviderWithClient(client, reactContext);
Expand Down
30 changes: 30 additions & 0 deletions packages/sdk/react/temp_docs/MIGRATING.md
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Expand Up @@ -179,6 +179,36 @@ state when initialization completes or when `client.identify()` is called.

---

## Bootstrap

### Old SDK

Bootstrap data was passed nested inside `options`:

```tsx
// HOC
withLDProvider({ clientSideID: 'your-id', options: { bootstrap: myData } })(App);

// Async HOC
const LDProvider = await asyncWithLDProvider({ clientSideID: 'your-id', options: { bootstrap: myData } });
```

### New SDK

Bootstrap is a first-class option on `createLDReactProvider`:

```tsx
import { createLDReactProvider } from '@launchdarkly/react-sdk';

const LDProvider = createLDReactProvider('your-client-side-id', { kind: 'user', key: 'user-key' }, {
bootstrap: myData,
});
```

The `bootstrap` data format is unchanged from the old SDK. You can pass either a plain key-value
object (`{ 'my-flag': true }`) or the output of `allFlagsState().toJSON()`, which includes
`$flagsState` and `$valid` metadata.

## Removed APIs

| Old API | Status | Replacement |
Expand Down
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