Motivation

After having some thought on the current abstraction model I have decided to make the abstraction much looser to allow for more provider-led customizations. In particular the filters in GrowthBook form general expressions and are not tied to per context property filtering. This should allow more flexibility in driving features within Excos Platform and enable me to incorporate more 3rd party feature providers.

Breaking Changes

1. Removed the IFeatureVariantOverride in order for the client to not be concerned with feature overrides. Those should be implemented via other means (e.g. a custom ILoadContextualOptions)
2. Removed Allocation from the data model. It can be implemented by each provider as a special filter and it can be skipped for settings which are not allocated per user/session.
3. Generalized filters over the whole context instead of being applied per property - this allows more flexible filtering logic and some performance optimizations compared to previous implementation.
4. Variant priority is now mandatory.
5. FeatureMetadata type that was used for injecting resolved variants as part of the options has been removed. Instead user should call the IFeatureEvaluation interface to get the list of resolved variants and their Ids.
6. The builder interface for in code feature specification is changed a little to account for model changes.
7. ExcosOptions class has been removed. Instead UserId is the default allocation unit for configuration provided features. You can no longer set the default globally.

Testing

I had some unit tests and they gave some confidence, but I feel like I could have missed something, so I may need to add more tests.

• Add more tests to verify no accidental breaking changes.

Performance

By changing the abstraction model of filters and then pushing in on the IOptionsContext constraint, I was able to redesign how filtering is executed for the configuration based provider. Excos.Options is now in the same ballpark as Microsoft.FeatureManagement.

Object pools have been removed as they don't seem to be adding much positive value (allocations stay in gen 0).

GrowthBook

I was able to properly implement the GB specification (with some caveats) so now most of the unit tests are actually passing. The ones that don't have been listed in the comment as exceptions with explanations why my implementation differs.

Docs

I've updated the GB Guide and Usage docs to reflect the changes.