fix: getFeatureFlagPayload wasn't sending the event

[marandaneto]

💡 Motivation and Context

PostHog/posthog-flutter#161 for Android
iOS would need to do the same.

💚 How did you test it?

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

[marandaneto]

before merging this, I'd like to ask if there's a reason why this is not done on the JS SDK either, since we ported the code from there.
https://github.com/PostHog/posthog-js/blob/1a5ce0bf6a7f77c44499de792ad4ec7aa45b8aa5/src/posthog-featureflags.ts#L358-L361

[rafaeelaudibert]

@marandaneto I believe it's intentional in posthog-js. You can see that we actually use getFeatureFlagPayload() inside the code that actually sends the $feature_flag_called event: https://github.com/PostHog/posthog-js/blob/1a5ce0bf6a7f77c44499de792ad4ec7aa45b8aa5/src/posthog-featureflags.ts#L346. We definitely don't want two captures in that case.

This is all very intricate in the posthog-js library, we might need to decouple that a little to figure out how this should behave. It sucks that our SDKs aren't consistent - something the sdk-team-whom-shouldnt-be-mentioned could work on.

The android SDK, for example, is sending much less information than the js SDK, even after your changes.

[ioannisj]

Another difference I see is that we don't seem to include $feature_flag_payload property in $feature_flag_called event on mobile (at least on iOS)

[marandaneto]

$feature_flag_payload

that is new, not added to all SDKs yet

[marandaneto]

@marandaneto I believe it's intentional in posthog-js. You can see that we actually use getFeatureFlagPayload() inside the code that actually sends the $feature_flag_called event: PostHog/posthog-js@1a5ce0b/src/posthog-featureflags.ts#L346. We definitely don't want two captures in that case.

This is all very intricate in the posthog-js library, we might need to decouple that a little to figure out how this should behave. It sucks that our SDKs aren't consistent - something the sdk-team-whom-shouldnt-be-mentioned could work on.

The android SDK, for example, is sending much less information than the js SDK, even after your changes.

Most of the new props are new https://github.com/PostHog/posthog-js/pull/1567/files
they just did not port to all SDKs yet

I think its intentional that getFeatureFlagPayload does not capture $feature_flag_called, so it's better to be clear about that first, I don't recall the reason, though.

[marandaneto]

Closing it until @PostHog/team-feature-flags tell what's the way forward here