Support contextual variant service provider and feature status fallback - #611
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zhiyuanliang-ms wants to merge 1 commit into
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Support contextual variant service provider and feature status fallback#611zhiyuanliang-ms wants to merge 1 commit into
zhiyuanliang-ms wants to merge 1 commit into
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| ServiceProvider serviceProvider = services.BuildServiceProvider(); | ||
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| IVariantFeatureManager featureManager = serviceProvider.GetRequiredService<IVariantFeatureManager>(); |
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featureManager can be removed
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| if (useContext) | ||
| { | ||
| enabled = await _featureManager.IsEnabledAsync(_featureName, context, cancellationToken); | ||
| } | ||
| else | ||
| { | ||
| enabled = await _featureManager.IsEnabledAsync(_featureName, cancellationToken); | ||
| } |
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Pull request overview
This PR expands the variant-service injection capabilities in the Feature Management .NET SDK by introducing a contextual variant service provider API and adding an optional “feature enabled/disabled” fallback path when no variant-based service can be resolved.
Changes:
- Introduces
IContextualVariantServiceProvider<TService>and updates the internalVariantServiceProvider<TService>to support context-aware evaluation. - Adds
WithVariantService<TService, TEnabled, TDisabled>(featureName)to allow falling back to an enabled/disabled implementation when variant resolution fails. - Refactors and extends tests into a dedicated
VariantServiceProviderTestsuite, including new coverage for contextual behavior and feature-status fallback.
Reviewed changes
Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| tests/Tests.FeatureManagement/VariantServices.cs | Adds alias-based test implementations used by new variant/fallback tests. |
| tests/Tests.FeatureManagement/VariantServiceProviderTest.cs | New test suite covering variant DI, keyed service resolution, contextual provider behavior, and status fallback. |
| tests/Tests.FeatureManagement/FeatureManagementTest.cs | Removes variant service provider tests that were moved to the new dedicated test file. |
| tests/Tests.FeatureManagement/AppContext.cs | Adds an additional context type for tests (currently unused). |
| src/Microsoft.FeatureManagement/VariantServiceProvider.cs | Implements contextual service retrieval and optional feature-status fallback. |
| src/Microsoft.FeatureManagement/IContextualVariantServiceProvider.cs | New public interface for contextual variant service providers. |
| src/Microsoft.FeatureManagement/FeatureManagementBuilderExtensions.cs | Adds new DI builder overload enabling feature-status fallback and registers contextual provider interface. |
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| // | ||
| // No implementation resolved from a variant. Fall back to the feature status. | ||
| bool enabled; | ||
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| /// <summary> | ||
| /// Adds a <see cref="VariantServiceProvider{TService}"/> to the feature management system that falls back to the feature status when no variant is assigned. | ||
| /// </summary> | ||
| /// <param name="builder">The <see cref="IFeatureManagementBuilder"/> used to customize feature management functionality.</param> | ||
| /// <param name="featureName">The feature flag that should be used to determine which implementation of the service should be used. The <see cref="VariantServiceProvider{TService}"/> will return the implementation matching the assigned variant, or, when no variant is assigned, <typeparamref name="TEnabled"/> if the feature is enabled and <typeparamref name="TDisabled"/> if it is disabled.</param> |
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| /// <summary> | ||
| /// Gets an implementation variant of TService, using the provided context to evaluate contextual feature filters when determining the assigned variant. | ||
| /// </summary> | ||
| /// <typeparam name="TContext">The type of the context.</typeparam> | ||
| /// <param name="context">A context that provides information used to evaluate contextual feature filters and to determine which variant will be assigned.</param> | ||
| /// <param name="cancellationToken">The cancellation token to cancel the operation.</param> | ||
| /// <returns>An implementation of TService.</returns> |
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| class AccountContext : IAccountContext | ||
| { | ||
| public string AccountId { get; set; } | ||
| } |
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Why this PR?
#604 #608
IVariantServiceProvider<TService>.GetServiceAsynccurrently does not accept a context, which limits it to scenarios that rely on ambient context.This creates a capability gap between
VariantServiceProviderandIVariantFeatureManager, because bothIVariantFeatureManager.IsEnabledAsyncandIVariantFeatureManager.GetVariantAsyncprovide overloads that accept an explicit context.How to fix
This PR introduces
IContextualVariantServiceProvider<TService>with methodGetServiceAsync<TContext>(TContext context, CancellationToken cancellationToken)The PR also adds
WithVariantService<TService, TEnabled, TDisabled>(featureName)which supports falling back to a service based on the feature’s enabled or disabled status.Service resolution behavior
Service resolution follows these steps:
GetVariantAsync.GetVariantAsynconly acceptsITargetingContext, so a non-targeting context is not used during variant resolution.TEnabled.TDisabled.Because
IsEnabledAsyncaccepts an arbitraryTContext, the feature-status fallback honors the supplied context even when it does not implementITargetingContext.