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Allow a feature flag to require all registered feature filters be enabled. #192

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Allow a feature flag to require all registered feature filters be enabled. #192

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18 changes: 18 additions & 0 deletions src/Microsoft.FeatureManagement/ConfigurationFeatureFlagDefinitionProvider.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ sealed class ConfigurationFeatureFlagDefinitionProvider : IFeatureFlagDefinition
private const string FeatureManagementSectionName = "FeatureManagement";
private const string FeatureFlagDefinitionsSectionName = "FeatureFlags";
private const string FeatureFiltersSectionName = "EnabledFor";
private const string RequirementTypeKeyword = "RequirementType";
private readonly IConfiguration _configuration;
private readonly ConcurrentDictionary<string, FeatureFlagDefinition> _featureFlagDefinitions;
private IDisposable _changeSubscription;
Expand Down Expand Up @@ -125,6 +126,8 @@ We support

Debug.Assert(configurationSection != null);

RequirementType requirementType = RequirementType.Any;

var enabledFor = new List<FeatureFilterConfiguration>();

string val = configurationSection.Value; // configuration[$"{featureName}"];
Expand All @@ -149,6 +152,20 @@ We support
}
else
{
string rawRequirementType = configurationSection[RequirementTypeKeyword];

if (!string.IsNullOrEmpty(rawRequirementType))
{
if (!Enum.TryParse(rawRequirementType, true, out RequirementType r))
{
throw new FeatureManagementException(
FeatureManagementError.InvalidConfiguration,
$"Invalid requirement type value for feature {configurationSection.Key}.");
}

requirementType = r;
}

IEnumerable<IConfigurationSection> filterSections = configurationSection.GetSection(FeatureFiltersSectionName).GetChildren();

foreach (IConfigurationSection section in filterSections)
Expand All @@ -171,6 +188,7 @@ We support
{
Name = configurationSection.Key,
EnabledFor = enabledFor,
RequirementType = requirementType
};
}

Expand Down
6 changes: 6 additions & 0 deletions src/Microsoft.FeatureManagement/FeatureFlagDefinition.cs
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Expand Up @@ -20,5 +20,11 @@ public class FeatureFlagDefinition
/// The feature filters that the feature flag can be enabled for.
/// </summary>
public IEnumerable<FeatureFilterConfiguration> EnabledFor { get; set; } = Enumerable.Empty<FeatureFilterConfiguration>();

/// <summary>
/// Determines whether any or all registered feature filters must be enabled for the feature to be considered enabled
/// The default value is <see cref="RequirementType.Any"/>.
/// </summary>
public RequirementType RequirementType { get; set; } = RequirementType.Any;
}
}
81 changes: 48 additions & 33 deletions src/Microsoft.FeatureManagement/FeatureManager.cs
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Expand Up @@ -82,7 +82,7 @@ private async Task<bool> IsEnabledAsync<TContext>(string feature, TContext appCo
}
}

bool enabled = false;
bool flagEnabled = false;

FeatureFlagDefinition featureDefinition = await _featureDefinitionProvider.GetFeatureFlagDefinitionAsync(feature, cancellationToken).ConfigureAwait(false);

Expand All @@ -94,7 +94,7 @@ private async Task<bool> IsEnabledAsync<TContext>(string feature, TContext appCo

if (featureDefinition.EnabledFor.Any(featureFilter => string.Equals(featureFilter.Name, "AlwaysOn", StringComparison.OrdinalIgnoreCase)))
{
enabled = true;
flagEnabled = true;
}
else
{
Expand All @@ -104,6 +104,8 @@ private async Task<bool> IsEnabledAsync<TContext>(string feature, TContext appCo

foreach (FeatureFilterConfiguration featureFilterConfiguration in featureDefinition.EnabledFor)
{
bool filterEnabled = false;

if (string.IsNullOrEmpty(featureFilterConfiguration.Name))
{
throw new FeatureManagementException(
Expand All @@ -125,48 +127,61 @@ private async Task<bool> IsEnabledAsync<TContext>(string feature, TContext appCo
{
_logger.LogWarning(errorMessage);
}

continue;
}

var context = new FeatureFilterEvaluationContext()
{
FeatureFlagName = featureDefinition.Name,
Parameters = featureFilterConfiguration.Parameters
};

//
// IFeatureFilter
if (filter is IFeatureFilter featureFilter)
else
{
if (await featureFilter.EvaluateAsync(context, cancellationToken).ConfigureAwait(false))
var context = new FeatureFilterEvaluationContext()
{
enabled = true;
FeatureFlagName = featureDefinition.Name,
Parameters = featureFilterConfiguration.Parameters
};

break;
//
// IFeatureFilter
if (filter is IFeatureFilter featureFilter)
{
filterEnabled = await featureFilter.EvaluateAsync(context, cancellationToken).ConfigureAwait(false);
}
//
// IContextualFeatureFilter
else if (useAppContext &&
TryGetContextualFeatureFilter(featureFilterConfiguration.Name, typeof(TContext), out ContextualFeatureFilterEvaluator contextualFilter))
{
filterEnabled = await contextualFilter.EvaluateAsync(context, appContext, cancellationToken).ConfigureAwait(false);
}
//
// The filter doesn't implement a feature filter interface capable of performing the evaluation
else
{
throw new FeatureManagementException(
FeatureManagementError.InvalidFeatureFilter,
useAppContext ?
$"The feature filter '{featureFilterConfiguration.Name}' specified for the feature '{feature}' is not capable of evaluating the requested feature with the provided context." :
$"The feature filter '{featureFilterConfiguration.Name}' specified for the feature '{feature}' is not capable of evaluating the requested feature.");
}
}
//
// IContextualFeatureFilter
else if (useAppContext &&
TryGetContextualFeatureFilter(featureFilterConfiguration.Name, typeof(TContext), out ContextualFeatureFilterEvaluator contextualFilter))

if (featureDefinition.RequirementType == RequirementType.Any)
{
if (await contextualFilter.EvaluateAsync(context, appContext, cancellationToken).ConfigureAwait(false))
if (filterEnabled)
{
enabled = true;
flagEnabled = true;

break;
}
}
//
// The filter doesn't implement a feature filter interface capable of performing the evaluation
else
else /* require all filters */
{
throw new FeatureManagementException(
FeatureManagementError.InvalidFeatureFilter,
useAppContext ?
$"The feature filter '{featureFilterConfiguration.Name}' specified for the feature '{feature}' is not capable of evaluating the requested feature with the provided context." :
$"The feature filter '{featureFilterConfiguration.Name}' specified for the feature '{feature}' is not capable of evaluating the requested feature.");
if (!filterEnabled)
{
flagEnabled = false;

break;
}

//
// True unless short-circuited as false
flagEnabled = true;
}
}
}
Expand All @@ -187,10 +202,10 @@ private async Task<bool> IsEnabledAsync<TContext>(string feature, TContext appCo

foreach (ISessionManager sessionManager in _sessionManagers)
{
await sessionManager.SetAsync(feature, enabled, cancellationToken).ConfigureAwait(false);
await sessionManager.SetAsync(feature, flagEnabled, cancellationToken).ConfigureAwait(false);
}

return enabled;
return flagEnabled;
}

private IFeatureFilterMetadata GetFeatureFilterMetadata(string filterName)
Expand Down
6 changes: 3 additions & 3 deletions ...eManagement.AspNetCore/RequirementType.cs → ...soft.FeatureManagement/RequirementType.cs
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Expand Up @@ -4,16 +4,16 @@
namespace Microsoft.FeatureManagement
{
/// <summary>
/// Describes whether any or all features in a given set should be required to be considered enabled.
/// Describes whether any or all conditions in a set should be required to be true.
/// </summary>
public enum RequirementType
{
/// <summary>
/// The enabled state will be attained if any feature in the set is enabled.
/// The set of conditions will be evaluated as true if any condition in the set is true.
/// </summary>
Any,
/// <summary>
/// The enabled state will be attained if all features in the set are enabled.
/// The set of conditions will be evaluated as true if all the conditions in the set are true.
/// </summary>
All
}
Expand Down
44 changes: 44 additions & 0 deletions tests/Tests.FeatureManagement/FeatureManagement.cs
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Expand Up @@ -30,6 +30,8 @@ public class FeatureManagement
private const string ContextualFeature = "ContextualFeature";
private const string WithSuffixFeature = "WithSuffixFeature";
private const string WithoutSuffixFeature = "WithoutSuffixFeature";
private const string AnyFilterFeature = "AnyFilterFeature";
private const string AllFiltersFeature = "AllFiltersFeature";

[Fact]
public async Task ReadsConfiguration()
Expand Down Expand Up @@ -209,6 +211,48 @@ public async Task AllowsSuffix()
Assert.True(called);
}

[Fact]
public async Task UsesRequirementType()
{
IConfiguration config = new ConfigurationBuilder().AddJsonFile("appsettings.json").Build();

var services = new ServiceCollection();

services
.AddSingleton(config)
.AddFeatureManagement()
.AddFeatureFilter<TestFilter>()
.AddFeatureFilter<Test2Filter>();

ServiceProvider serviceProvider = services.BuildServiceProvider();

IFeatureManager featureManager = serviceProvider.GetRequiredService<IFeatureManager>();

IEnumerable<IFeatureFilterMetadata> featureFilters = serviceProvider.GetRequiredService<IEnumerable<IFeatureFilterMetadata>>();

TestFilter testFeatureFilter = (TestFilter)featureFilters.First(f => f is TestFilter && !(f is Test2Filter));

Test2Filter testFeatureFilter2 = (Test2Filter)featureFilters.First(f => f is Test2Filter);

testFeatureFilter.Callback = testFeatureFilter2.Callback = (evaluationContext) => Task.FromResult(false);

Assert.False(await featureManager.IsEnabledAsync(AnyFilterFeature, CancellationToken.None));

Assert.False(await featureManager.IsEnabledAsync(AllFiltersFeature, CancellationToken.None));

testFeatureFilter.Callback = testFeatureFilter2.Callback = (evaluationContext) => Task.FromResult(true);

Assert.True(await featureManager.IsEnabledAsync(AnyFilterFeature, CancellationToken.None));

Assert.True(await featureManager.IsEnabledAsync(AllFiltersFeature, CancellationToken.None));

testFeatureFilter2.Callback = (evaluationContext) => Task.FromResult(false);

Assert.True(await featureManager.IsEnabledAsync(AnyFilterFeature, CancellationToken.None));

Assert.False(await featureManager.IsEnabledAsync(AllFiltersFeature, CancellationToken.None));
}

[Fact]
public async Task Integrates()
{
Expand Down
6 changes: 6 additions & 0 deletions tests/Tests.FeatureManagement/TestFilter.cs
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Expand Up @@ -17,4 +17,10 @@ public Task<bool> EvaluateAsync(FeatureFilterEvaluationContext context, Cancella
return Callback?.Invoke(context) ?? Task.FromResult(false);
}
}

//
// Offers the same functionality as TestFilter, but allows a feature used in tests to reference two different filters
class Test2Filter : TestFilter
{
}
}
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