All keys being evaluated and returned when requesting specific ones

[obedparla]

Describe the bug
Hey guys,

Whenever a connection is made with withLDProvider using the flags option, all keys are evaluated in LaunchDarkly, and all of them are returned in the network response, even though only the requested one in the flags option is available through the code.

I'm not sure if this is intended behavior, I'm doing something wrong, or if it's a bug. But clarification would be greatly appreciated 🙏. I'm assuming it's a bug because the documentation states

flags: If specified, the React SDK will only request and subscribe for updates to these flags. The React SDK will request for and subscribe to all flags when this property is unspecified. This property is optional.

Docs here

To reproduce
Here's my code:

const MyExtendedComp = withLDProvider({
  clientSideID: clientsideId,
  user: {
    key: userKey,
    custom: {
      'operator-id': operatorId,
    },
  },
  flags: {
    'admin-my-key': false,
  },
})(MyComponent);

Expected behavior
I'd expect that LD only evaluates and returns the flag I'm requesting. In this case admin-my-key and not all of them only to filter it out in the client.

SDK version
"launchdarkly-react-client-sdk": "^2.18.0",

[obedparla]

I landed on this issue launchdarkly/js-client-sdk#193 (comment) on the JS SDK, and they explain that the flags are always evaluated, but that the analytics will only be affected by the flags we request. Can someone confirm this is the case?

[bwoskow-ld]

Hi @obedparla,

What you've described is intended behavior. The entire flag set, regardless of whether or not individual flags are specified in the flags property, are included in the requests between LaunchDarkly and your SDK instance on SDK initialization and on changing users. The filtering happens within the React SDK as a post-function after those flags are received from LaunchDarkly.

You're correct in calling out a mistake in our docs. I remember personally adding that doc content when we last spoke on this topic. I'll submit a PR to update the docs so that it doesn't say that the SDK will only request for specified flags.

[obedparla]

Cheers, thank you for the clarification @bwoskow-ld.

Is it correct to assume that the analytics are not affected by this, and only the requested flags will be recorded as "used"?

I'll do some validation on our end to make sure this is the case, but I'd like to confirm the intended behavior of the SDK

[bwoskow-ld]

That is correct. Analytics (evaluation events) are sent once per flag in the flags object. Flags not specified in this object will not have corresponding events published to LaunchDarkly.

[obedparla]

Thank you for clarifying! Have a great day :)