Bug in local evaluation of feature flags without multivariates when calling GetFeatureFlag

[dpovey]

I have a boolean flag that is defined with filters with seperate rollout percentages.

Here is a rough structure of the flag

flag posthog.FeatureFlag = {
  Key = ...
  IsSimpleFlag = false
  RolloutPercentage = nil
  Active = true
  Filters = {
    AggregationGroupTypeIndex = nil
    Groups = [
        { 
            Properties = ...
            RolloutPercentage = 50
            Variant = nil
        },
        ...
    ],
    Multivariate = nil,
   Payloads = {}
   }
   EnsureExperienceContinuity = false
  }

I can see that my condition matches in matchFeatureFlagProperties, but in the processing of this code:

if isMatch {
  		variantOverride := condition.Variant
  		multivariates := flag.Filters.Multivariate

  		if variantOverride != nil && multivariates != nil && multivariates.Variants != nil && containsVariant(multivariates.Variants, *variantOverride) {
  			return *variantOverride, nil
  		} else {
  			return getMatchingVariant(flag, distinctId)
  		}
  	}

It doesn't correctly handle the case where there are no variants. It calls getMatchingVariant when it could just cal checkIfSimpleFlagEnabled like so:

                if isMatch {
			variantOverride := condition.Variant
			multivariates := flag.Filters.Multivariate

			if variantOverride != nil && multivariates != nil && multivariates.Variants != nil && containsVariant(multivariates.Variants, *variantOverride) {
				return *variantOverride, nil
			} else if multivariates == nil || multivariates.Variants == nil || len(multivariates.Variants) == 0 {
				// Handle boolean flag with condition-specific rollout percentage
				if condition.RolloutPercentage != nil {
					return checkIfSimpleFlagEnabled(flag.Key, distinctId, *condition.RolloutPercentage)
				}
				return true, nil
			} else {
				return getMatchingVariant(flag, distinctId)
			}
		}

Or perhaps some variation that has a different salt. This is preventing me being able to use Posthog as I need to be able to locally evaluate these flags.