feat: Openfeature Provider implementation powered by DD Flags

[typotter]

What does this PR do?

This PR adds a new OpenFeature provider module (dd-sdk-android-flags-openfeature) that integrates the Datadog Feature Flags SDK with the OpenFeature API, enabling developers to use standardized feature flag management while leveraging Datadog's observability platform.

Key components:

• DatadogFlagsProvider: OpenFeature FeatureProvider implementation that adapts the OpenFeature API to Datadog's FlagsClient
• Type Converters: Bidirectional conversion between OpenFeature Values and JSON types, preserving type information
• Factory Methods: Three factory methods (create(), create(name), create(name, sdkCore)) for flexible provider instantiation, paralleling FlagsClient's create methods
• Extension Function: FlagsClient.asOpenFeatureProvider() for convenient wrapping of existing clients
• Static-Context Paradigm: Implements OpenFeature's static-context model with global context management

Motivation

Why OpenFeature Integration?

1. Standardization: OpenFeature provides a vendor-neutral, community-driven specification for feature flagging
2. Ecosystem: Enables integration with OpenFeature-compatible tools and libraries
3. Migration Path: Allows customers to adopt OpenFeature API while using Datadog as the backend
4. Multi-Vendor: Customers can switch between feature flag providers without code changes

Additional Notes

Architecture Decisions

Static-Context Paradigm

• This provider implements the static-context paradigm per OpenFeature spec
• Global context is set via OpenFeatureAPI.setEvaluationContext()
• Per-evaluation (invocation) contexts are not supported - OpenFeature spec does not support invocation contexts in static-paradigm providers

Type Conversion Strategy

• JSON → OpenFeature Value: Intelligent type promotion (e.g., Long within Int range becomes Value.Integer)
• OpenFeature Value → JSON: Preserves type information (Integer→Int, Boolean→Boolean)
• Null Handling: JSONObject.NULL sentinel values are converted to Value.Null
• Special Values: Handles NaN, Infinity, nested structures, large collections

Error Handling

• Specific exception catching (JSONException, ClassCastException, IllegalStateException)
• Appropriate OpenFeature error codes (PARSE_ERROR, TYPE_MISMATCH, GENERAL)
• Graceful degradation - returns default values on errors
• Comprehensive logging for debugging

Thread Safety

• Provider methods are thread-safe, delegating coordination to FlagsClient
• No synchronization locks (upstream FlagsClient handles concurrency)

Implementation Details

Module Structure:

dd-sdk-android-flags-openfeature/
├── DatadogFlagsProvider.kt       # Main provider implementation
├── FlagsClientExt.kt             # Extension function
└── internal/adapters/
    ├── Converters.kt             # Context & error code converters
    └── ValueConverters.kt        # JSON ↔ OpenFeature Value converters

Test Coverage:

• new unit tests

CI/CD Integration:

• Added to detekt pipeline (:features:dd-sdk-android-flags-openfeature:customDetektRules)
• Publishing configured (publish:release-flags-openfeature)
• License compliance updated (Apache-2.0 for OpenFeature)

Known Limitations & Future Work

TODO FFL-1442: Implement observe() method for provider state observation

• Requires upstream changes in flags module to expose FlagsClient state changes
• Currently uses default implementation (returns empty Flow)

Manual Testing:

val provider = DatadogFlagsProvider.create()
OpenFeatureAPI.setProviderAndWait(provider)
val client = OpenFeatureAPI.getClient()
val isEnabled = client.getBooleanValue("my-feature", false)

Review checklist (to be filled by reviewers)

• [ ] Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• [ ] Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• [ ] Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

:x: Patch coverage is 47.23247% with 143 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 70.86%. Comparing base (6c2f8ab) to head (ef411d2).

Files with missing lines	Patch %	Lines
.../android/flags/openfeature/DatadogFlagsProvider.kt	23.08%	81 Missing and 9 partials :warning:
...s/openfeature/internal/adapters/ValueConverters.kt	68.52%	12 Missing and 5 partials :warning:
.../flags/openfeature/internal/adapters/Converters.kt	57.14%	14 Missing and 1 partial :warning:
...in/kotlin/com/datadog/android/flags/FlagsClient.kt	0.00%	13 Missing :warning:
...atadog/android/flags/internal/FlagsStateManager.kt	86.36%	3 Missing :warning:
.../datadog/android/flags/internal/NoOpFlagsClient.kt	50.00%	2 Missing :warning:
...id/flags/internal/evaluation/EvaluationsManager.kt	93.33%	1 Missing :warning:
...lags/internal/repository/DefaultFlagsRepository.kt	0.00%	0 Missing and 1 partial :warning:
...om/datadog/android/flags/model/FlagsClientState.kt	83.33%	1 Missing :warning:

Additional details and impacted files

@@                   Coverage Diff                   @@
##           feature/flags-ofeat    #2998      +/-   ##
=======================================================
- Coverage                71.10%   70.86%   -0.24%     
=======================================================
  Files                      860      865       +5     
  Lines                    31311    31565     +254     
  Branches                  5275     5334      +59     
=======================================================
+ Hits                     22263    22368     +105     
- Misses                    7556     7673     +117     
- Partials                  1492     1524      +32     

Files with missing lines	Coverage Δ
...atadog/android/flags/openfeature/FlagsClientExt.kt	100.00% <100.00%> (ø)
...tadog/android/flags/internal/DatadogFlagsClient.kt	88.41% <100.00%> (-1.30%)	:arrow_down:
...id/flags/internal/evaluation/EvaluationsManager.kt	91.18% <93.33%> (+1.89%)	:arrow_up:
...lags/internal/repository/DefaultFlagsRepository.kt	64.00% <0.00%> (-1.31%)	:arrow_down:
...om/datadog/android/flags/model/FlagsClientState.kt	83.33% <83.33%> (ø)
.../datadog/android/flags/internal/NoOpFlagsClient.kt	93.10% <50.00%> (-6.90%)	:arrow_down:
...atadog/android/flags/internal/FlagsStateManager.kt	86.36% <86.36%> (ø)
...in/kotlin/com/datadog/android/flags/FlagsClient.kt	35.59% <0.00%> (-2.59%)	:arrow_down:
.../flags/openfeature/internal/adapters/Converters.kt	57.14% <57.14%> (ø)
...s/openfeature/internal/adapters/ValueConverters.kt	68.52% <68.52%> (ø)
... and 1 more

... and 37 files with indirect coverage changes

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[datadog-datadog-prod-us1[bot]]

🎯 Code Coverage
• Patch Coverage: 100.00%
• Total Coverage: 71.03% (-0.22%)
View detailed report

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