Added support for AppConfig Feature Flag profiles #229

sandbrock-nd · 2025-06-18T04:34:42Z

Added support for AppConfig Feature Flag profiles by allowing the consumer to nest the resulting JSON in a named parent node.

Description

This aims to allow consumers to inject feature flags into their application. The user cannot control the schema for AppConfig Feature Flag profiles because they are controlled by AWS. The JSON format is like this:

{"test-flag-1":{"enabled":false},"test-flag-2":{"enabled":true}}

This is not friendly with the .NET builder.Configuration system because there is no named wrapper node around the list of feature flags. The result is that each flag is nested directly under the root of the configuration hierarchy.

This update allows the consumer to pass in the name of a wrapper node to nest the AppConfig JSON inside of by using the extension method for AppConfig registration:

    builder.Configuration.AddAppConfig(new AppConfigConfigurationSource()
    {
        ApplicationId = "application",
        EnvironmentId = "Default",
        ConfigProfileId = "my-appconfig-feature-profile",
        AwsOptions = new AWSOptions(),
        ReloadAfter = new TimeSpan(0, 0, 30),
        WrapperNodeName = "FeatureFlags"
    })

And then read the values from that configuration profile, by deserializing the JSON into a dictionary of feature flag class instances:

builder.Services.Configure<Dictionary<string, AppConfigFeatureFlag>(builder.Configuration.GetSection("FeatureFlags"));

Motivation and Context

The end goal is to allow the consumer to inject feature flags into their controllers and minimal API class constructors, such as in the following:

MyConstructor(IOptionsMonitor<Dictionary<string, AppConfigFeatureFlag>> featureFlags)

This addresses the following feature request:
#228

Testing

Initial testing was done by creating a unit test. Follow-up testing was done by integrating the library into an application that consumed both configuration profiles and feature flag profiles. The tests validated both profiles loaded correctly and were injected into the services DI container.

Screenshots (if appropriate)

Types of changes

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Breaking change (fix or feature that would cause existing functionality to change)

Checklist

My code follows the code style of this project
My change requires a change to the documentation
I have updated the documentation accordingly
I have read the README document
I have added tests to cover my changes
All new and existing tests passed

License

I confirm that this pull request can be released under the Apache 2 license

GarrettBeatty · 2025-07-17T16:34:34Z

reviewing this now

Copilot

Pull Request Overview

Adds support for AppConfig Feature Flag profiles by wrapping AWS AppConfig JSON under a consumer-defined parent node.

Introduces WrapperNodeName on the configuration source and surfaces it in the extension methods
Implements AddWrapperNodeAsync in AppConfigProcessor and applies it in the service-based retrieval path
Adds a unit test for the new wrapper logic and updates the README sample to demonstrate usage

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Amazon.Extensions.Configuration.SystemsManager/AppConfig/AppConfigConfigurationSource.cs	Added `WrapperNodeName` property
src/Amazon.Extensions.Configuration.SystemsManager/AppConfig/AppConfigExtensions.cs	Extended `ConfigureSource` signature to include `wrapperNodeName`
src/Amazon.Extensions.Configuration.SystemsManager/AppConfig/AppConfigProcessor.cs	Implemented `AddWrapperNodeAsync` and applied it in `GetDataFromServiceAsync`
test/Amazon.Extensions.Configuration.SystemsManager.Tests/AppConfigProcessorTests.cs	Added unit test for `AddWrapperNodeAsync` via reflection
README.md	Updated sample code to show how to configure and consume the wrapper

Comments suppressed due to low confidence (3)

README.md:224

Add using System.Text.Json.Serialization; at the top of this sample so the [JsonPropertyName] attribute is recognized.

    [JsonPropertyName("enabled")]

README.md:254

[nitpick] Per C# conventions, private fields should use camelCase (e.g., _featureFlags) instead of PascalCase.

    private readonly IOptionsMonitor<Dictionary<string, AppConfigFeatureFlag>> _FeatureFlags;

src/Amazon.Extensions.Configuration.SystemsManager/AppConfig/AppConfigExtensions.cs:235

The new wrapperNodeName parameter should be added to the XML documentation comments for this method to keep the API docs up to date.

        private static AppConfigConfigurationSource ConfigureSource(

Copilot · 2025-07-17T16:45:40Z

src/Amazon.Extensions.Configuration.SystemsManager/AppConfig/AppConfigProcessor.cs

+            var wrappedConfigBytes = System.Text.Encoding.UTF8.GetBytes(wrappedConfig);
+            await wrappedStream.WriteAsync(wrappedConfigBytes, 0, wrappedConfigBytes.Length).ConfigureAwait(false);
+            wrappedStream.Position = 0;
+        }

        private async Task<IDictionary<string,string>> GetDataFromLambdaExtensionAsync()


The WrapperNodeName wrapping is not applied in the GetDataFromLambdaExtensionAsync path, so feature-flag JSON returned by the Lambda extension won’t be nested. Consider invoking AddWrapperNodeAsync (as in the service path) before parsing when WrapperNodeName is set.

i was thinking about this comment. i couldn't think of a reason to not add the same logic here.

[Question] Can/should we add the new logic you added here too (or is there a specific reason you didn't)

GarrettBeatty · 2025-07-17T17:21:21Z

src/Amazon.Extensions.Configuration.SystemsManager/AppConfig/AppConfigProcessor.cs

+            var wrappedConfigBytes = System.Text.Encoding.UTF8.GetBytes(wrappedConfig);
+            await wrappedStream.WriteAsync(wrappedConfigBytes, 0, wrappedConfigBytes.Length).ConfigureAwait(false);
+            wrappedStream.Position = 0;
+        }

        private async Task<IDictionary<string,string>> GetDataFromLambdaExtensionAsync()


i was thinking about this comment. i couldn't think of a reason to not add the same logic here.

[Question] Can/should we add the new logic you added here too (or is there a specific reason you didn't)

GarrettBeatty · 2025-07-17T17:22:39Z

README.md

@@ -214,6 +214,51 @@ namespace CustomParameterProcessorExample
 }
 ```

+### Simple AppConfig FeatureFlag Sample


can you also add a change file for this change https://github.com/aws/aws-dotnet-extensions-configuration/blob/main/CONTRIBUTING.md#adding-a-change-file-to-your-contribution-branch

GarrettBeatty · 2025-07-17T17:26:34Z

thanks for the pr! i left a couple of small comments/questions @sandbrock-nd

philasmar · 2025-07-18T12:59:58Z

README.md

+//
+
+// Map feature flag configuration 
+builder.Services.Configure<Dictionary<string, AppConfigFeatureFlag>>(builder.Configuration.GetSection("FeatureFlags"));


Instead of injecting Dictionary<string, AppConfigFeatureFlag> into the DI container, why not create an AppConfigFeatureFlagConfiguration object that contains the dictionary you are trying to access? I'd prefer users to access the config using AppConfigFeatureFlagConfiguration instead of Dictionary<string, AppConfigFeatureFlag>

sandbrock-nd added 2 commits June 17, 2025 22:22

Added support for AppConfig Feature Flag profiles

9aa796b

Added support for AppConfig FeatureFlag profiles

af9e090

sandbrock-nd mentioned this pull request Jun 18, 2025

Add support for AppConfig FeatureFlag profiles. #228

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GarrettBeatty requested review from GarrettBeatty and philasmar June 20, 2025 17:15

GarrettBeatty requested a review from Copilot July 17, 2025 16:44

Copilot AI reviewed Jul 17, 2025

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GarrettBeatty changed the base branch from main to dev July 17, 2025 16:46

GarrettBeatty requested changes Jul 17, 2025

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Description

Motivation and Context

Testing

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Types of changes

Checklist

License

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