fix(browser): Accept precisely-typed GrowthBook class in growthbookIntegration

[codr]

Problem

Following the integration's own documented usage produces a TypeScript compile error. Copy-pasting the snippet from the growthbookIntegration JSDoc / docs:

import { GrowthBook } from '@growthbook/growthbook';
import * as Sentry from '@sentry/browser'; // or @sentry/react

Sentry.init({
  dsn: '...',
  integrations: [Sentry.growthbookIntegration({ growthbookClass: GrowthBook })],
});

fails to type-check against the real @growthbook/growthbook class:

error TS2322: Type 'typeof GrowthBook' is not assignable to type 'GrowthBookClass'.
  Type 'new <AppFeatures...>(options?: Options) => GrowthBook<AppFeatures>'
    is not assignable to type 'new (...args: unknown[]) => GrowthBook'.

So a consumer who does exactly what the docs say is forced to add a cast — e.g. growthbookClass: GrowthBook as unknown as ... — which is poor DX and directly contradicts the documented example. Reproduces on the latest release (10.62.0) via both @sentry/browser and @sentry/react.

Root cause

The parameter is typed as a constructor with unknown[] args:

export type GrowthBookClass = new (...args: unknown[]) => GrowthBook;        // @sentry/browser
export type GrowthBookClassLike = new (...args: unknown[]) => GrowthBookLike; // @sentry/core

GrowthBook's real constructor is constructor(options?: Options). A constructor with a narrow parameter is not assignable to one declared with (...args: unknown[]) — constructor parameters are contravariant, and unknown is not assignable to Options — so typeof GrowthBook is rejected.

This only surfaces through @sentry/browser / @sentry/react. @sentry/core annotates its export as IntegrationFn ((...rest: any[])), which erases the parameter type and hides the problem; @sentry/browser re-declares the wrapper with the strict { growthbookClass: GrowthBookClass } parameter (via satisfies IntegrationFn), preserving the strict type that the public API exposes.

Fix

The integration never constructs growthbookClass — it only reads growthbookClass.prototype to monkey-patch isOn / getFeatureValue. Typing the parameter as exactly that:

export type GrowthBookClass = { prototype: GrowthBook };
export type GrowthBookClassLike = { prototype: GrowthBookLike };

accepts any class whose instances expose the wrapped surface (so the documented typeof GrowthBook usage works with no cast), still rejects classes missing isOn / getFeatureValue, and avoids any. It also makes the internal growthbookClass.prototype as GrowthBookLike cast redundant, which is removed.

Test

Adds packages/browser/test/integrations/featureFlags/growthbook/integration.test.ts: passes a mock class with a real, narrow constructor to growthbookIntegration with no cast (the type regression guard) and asserts boolean evaluations are captured to the scope's flag context.

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• If you've added code that should be tested, please add tests.
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• No related issue is linked — happy to file one if preferred.