I am trying to setup feature flags via the flags sdk with the posthog provider.

Defining

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export const myTestFlag = flag({
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  key: "my-test-flag",
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  adapter: postHogAdapter.isFeatureEnabled(),
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});

is valid and TypeScript doesn't complain.

However it will throw an error:

Error: PostHog Adapter: Missing entities, flag must be defined with an identify() function.

In the docs this is simple referred to as:

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import identify from "@/lib/identify";
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export const myFlag = flag({
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  key: "posthog-is-feature-enabled",
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  adapter: postHogAdapter.isFeatureEnabled(),
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  identify,
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});

with no details how the identify function has to be implemented.

Adding an async function that returns the email as string or as an object {email: string} will lead to an error on the adapter:

After a while of digging it seems identify should return Promise<{distinctId: string}> . This would be a valuable addition to the docs as it's not obvious.

Additionally when a feature-flag is disabled in PostHog and the feature flag is implemented as shown in the docs this will lead to following error:

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Error: PostHog Adapter isFeatureEnabled returned undefined for my-test-flag and no default value was provided.

hence the documentation should contain the defaultValue:

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export const myTestFlag = flag({
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  key: "my-test-flag",
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  defaultValue: false,
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  adapter: postHogAdapter.isFeatureEnabled(),
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  identify,
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});