Add configuration-based feature value provider

docs/en/framework/infrastructure/features.md

@@ -395,8 +395,31 @@ There are three pre-defined value providers, executed by the given order:
 
 * `TenantFeatureValueProvider` tries to get if the feature value is explicitly set for the **current tenant**.
 * `EditionFeatureValueProvider` tries to get the feature value for the current edition. Edition Id is obtained from the current principal identity (`ICurrentPrincipalAccessor`) with the claim name `editionid` (a constant defined as`AbpClaimTypes.EditionId`). Editions are not implemented for the [tenant management](../../modules/tenant-management.md) module. You can implement it yourself or consider to use the [SaaS module](https://abp.io/modules/Volo.Saas) of the ABP Commercial.
+* `ConfigurationFeatureValueProvider`: Gets the value from the [IConfiguration service](../fundamentals/configuration.md).
 * `DefaultValueFeatureValueProvider` gets the default value of the feature.
 
+#### Feature Values in the Application Configuration
+
+The `ConfigurationFeatureValueProvider` reads the feature values from the `IConfiguration` service, which can read values from the `appsettings.json` by default. So, the easiest way to configure feature values is to define them in the `appsettings.json` file.
+
+For example, you can configure feature values as shown below:
+
+````json
+{
+  "Features": {
+    "MyApp.Reporting": "true",
+    "MyApp.PdfReporting": "true",
+    "MyApp.MaxProductCount": "50"
+  }
+}
+````
+
+Feature values should be configured under the `Features` section as like in this example.
+
+> `IConfiguration`  is an .NET Core service and it can read values not only from the `appsettings.json`, but also from the environment, user secrets... etc. See [Microsoft's documentation](https://docs.microsoft.com/en-us/aspnet/core/fundamentals/configuration/) for more.
+
+#### Custom Feature Value Providers
+
 You can write your own provider by inheriting the `FeatureValueProvider`.
 
 **Example: Enable all features for a user with "SystemAdmin" as a "User_Type" claim value**

docs/en/modules/feature-management.md

@@ -72,9 +72,10 @@ namespace Demo
 
 ## Feature Management Providers
 
-Features Management Module is extensible, just like the [features system](../framework/infrastructure/features.md).  You can extend it by defining feature management providers. There are 3 pre-built feature management providers registered it the following order:
+Features Management Module is extensible, just like the [features system](../framework/infrastructure/features.md).  You can extend it by defining feature management providers. There are 4 pre-built feature management providers registered in the following order:
 
 * `DefaultValueFeatureManagementProvider`: Gets the value from the default value of the feature definition. It can not set the default value since default values are hard-coded on the feature definition.
+* `ConfigurationFeatureManagementProvider`: Gets the value from the [IConfiguration service](../framework/fundamentals/configuration.md).
 * `EditionFeatureManagementProvider`: Gets or sets the feature values for an edition. Edition is a group of features assigned to tenants. Edition system has not implemented by the Tenant Management module. You can implement it yourself or purchase the ABP [SaaS Module](https://abp.io/modules/Volo.Saas) which implements it and also provides more SaaS features, like subscription and payment.
 * `TenantFeatureManagementProvider`: Gets or sets the features values for tenants.
 

framework/src/Volo.Abp.Features/Volo/Abp/Features/AbpFeaturesModule.cs

@@ -31,6 +31,7 @@ public override void ConfigureServices(ServiceConfigurationContext context)
         context.Services.Configure<AbpFeatureOptions>(options =>
         {
             options.ValueProviders.Add<DefaultValueFeatureValueProvider>();
+            options.ValueProviders.Add<ConfigurationFeatureValueProvider>();
             options.ValueProviders.Add<EditionFeatureValueProvider>();
             options.ValueProviders.Add<TenantFeatureValueProvider>();
         });

framework/src/Volo.Abp.Features/Volo/Abp/Features/ConfigurationFeatureValueProvider.cs

@@ -0,0 +1,26 @@
+using System.Threading.Tasks;
+using Microsoft.Extensions.Configuration;
+
+namespace Volo.Abp.Features;
+
+public class ConfigurationFeatureValueProvider : FeatureValueProvider
+{
+    public const string ConfigurationNamePrefix = "Features:";
+
+    public const string ProviderName = "C";
+
+    public override string Name => ProviderName;
+
+    protected IConfiguration Configuration { get; }
+
+    public ConfigurationFeatureValueProvider(IFeatureStore featureStore, IConfiguration configuration)
+        : base(featureStore)
+    {
+        Configuration = configuration;
+    }
+
+    public override Task<string?> GetOrNullAsync(FeatureDefinition feature)
+    {
+        return Task.FromResult(Configuration[ConfigurationNamePrefix + feature.Name]);
+    }
+}

modules/feature-management/src/Volo.Abp.FeatureManagement.Domain/Volo/Abp/FeatureManagement/AbpFeatureManagementDomainModule.cs

@@ -29,6 +29,7 @@ public override void ConfigureServices(ServiceConfigurationContext context)
         Configure<FeatureManagementOptions>(options =>
         {
             options.Providers.Add<DefaultValueFeatureManagementProvider>();
+            options.Providers.Add<ConfigurationFeatureManagementProvider>();
             options.Providers.Add<EditionFeatureManagementProvider>();
 
             //TODO: Should be moved to the Tenant Management module

modules/feature-management/src/Volo.Abp.FeatureManagement.Domain/Volo/Abp/FeatureManagement/ConfigurationFeatureManagementProvider.cs

@@ -0,0 +1,44 @@
+using System;
+using System.Threading.Tasks;
+using Microsoft.Extensions.Configuration;
+using Volo.Abp.DependencyInjection;
+using Volo.Abp.Features;
+
+namespace Volo.Abp.FeatureManagement;
+
+public class ConfigurationFeatureManagementProvider : IFeatureManagementProvider, ISingletonDependency
+{
+    public string Name => ConfigurationFeatureValueProvider.ProviderName;
+
+    protected IConfiguration Configuration { get; }
+
+    public ConfigurationFeatureManagementProvider(IConfiguration configuration)
+    {
+        Configuration = configuration;
+    }
+
+    public virtual bool Compatible(string providerName)
+    {
+        return providerName == Name;
+    }
+
+    public virtual Task<IAsyncDisposable> HandleContextAsync(string providerName, string providerKey)
+    {
+        return Task.FromResult<IAsyncDisposable>(NullAsyncDisposable.Instance);
+    }
+
+    public virtual Task<string> GetOrNullAsync(FeatureDefinition feature, string providerKey)
+    {
+        return Task.FromResult(Configuration[ConfigurationFeatureValueProvider.ConfigurationNamePrefix + feature.Name]);
+    }
+
+    public virtual Task SetAsync(FeatureDefinition feature, string value, string providerKey)
+    {
+        throw new AbpException($"Can not set a feature value to the application configuration.");
+    }
+
+    public virtual Task ClearAsync(FeatureDefinition feature, string providerKey)
+    {
+        throw new AbpException($"Can not set a feature value to the application configuration.");
+    }
+}

modules/feature-management/src/Volo.Abp.FeatureManagement.Domain/Volo/Abp/FeatureManagement/ConfigurationValueFeatureManagerExtensions.cs

@@ -0,0 +1,19 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using JetBrains.Annotations;
+using Volo.Abp.Features;
+
+namespace Volo.Abp.FeatureManagement;
+
+public static class ConfigurationValueFeatureManagerExtensions
+{
+    public static Task<string> GetOrNullConfigurationAsync(this IFeatureManager featureManager, [NotNull] string name, bool fallback = true)
+    {
+        return featureManager.GetOrNullAsync(name, ConfigurationFeatureValueProvider.ProviderName, null, fallback);
+    }
+
+    public static Task<List<FeatureNameValue>> GetAllConfigurationAsync(this IFeatureManager featureManager, bool fallback = true)
+    {
+        return featureManager.GetAllAsync(ConfigurationFeatureValueProvider.ProviderName, null, fallback);
+    }
+}