getFlagReason always undefined with allFlagsState response

[ClementLevesque]

Is this a support request? No.

Describe the bug

The method allFlagsState returns a Promise resolved by an object on which getFlagReason(key) returns always undefined :

const flagsState = await featureFlagClientInt.allFlagsState({ key });

// flagsState.getFlagReason(key) === undefined
// flagsState.allValues() & flagsState.getFlagValue() are ok 

Whereas featureDetail which returns the proper object :

const { reason, value } = await featureFlagClientInt.featureDetail(featureKey, { key }, false);
// reason.kind === 'OFF' || 'RULE_MATCH' etc.

To reproduce

• Create a feature flag in the dashboard
• Instanciate the LaunchDarklyClient
• Call allFlagsState on that client

Expected behavior getFlagReason should return a LDEvaluationReason object type.

Logs See above.

SDK version Current sdk version: launchdarkly-node-server-sdk: "5.13.4"

Language version, developer tools NodeJS 16.1.0

OS/platform On local env, Mac book pro M1.

Additional context Add any other context about the problem here.

[kinyoklion]

Hello @ClementLevesque,

By default allFlagsState does not include reasons for all flags. You can change the behavior by using LDFlagsStateOptions to indicate you want reasons.

await ldClient.allFlagsState({key}, {withReasons: true});

Thank you, Ryan

[eli-darkly]

Yes, that's what the API docs for getFlagReason mean when they say "it will be null if reasons were not recorded". Reasons are only recorded if you use the option Ryan mentioned.

As background, here's why the default is not to capture reasons. The most common use case for allFlagsState is to produce bootstrap data for initializing the JS SDK. That data will have to be passed in some way to the front end, such as by embedding it in a hidden HTML component, so it's desirable to not make it any bigger than necessary. And most front-end code that uses the JS SDK does not use evaluation reasons— getting them is an opt-in feature for client-side SDKs, even if you are connecting directly to LD and not using bootstrap data. So the reasons are omitted from that data by default.

[ClementLevesque]

It works ! Thanks a lot for your help and precious and detailed answer. I have to admit that the API docs could be more explicit about this option 😉