Merge pull request #5 from gsoft-inc/feature/cached-configuration-sou…

…rces

Caching configuration sources to prevent duplicating configuration providers

README.md

@@ -20,10 +20,6 @@ var builder = WebApplication.CreateBuilder(args);
 builder.Configuration.AddJsonFile("appsettings.json");
 builder.Configuration.AddEnvironmentVariables();
 builder.Configuration.AddSubstitution(); // <-- Add this after other configuration providers
-
-// Setup your services
-// [...]
-builder.Services.AddSubstitution(); // <-- Add also this to your service collection
 ```
 
 

src/GSoft.Extensions.Configuration.Substitution.Tests/GSoft.Extensions.Configuration.Substitution.Tests.csproj

@@ -8,7 +8,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="6.0.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.1.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3">

src/GSoft.Extensions.Configuration.Substitution/CachedConfigurationSource.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Diagnostics;
+using Microsoft.Extensions.Configuration;
+
+namespace GSoft.Extensions.Configuration.Substitution;
+
+[DebuggerDisplay("CachedConfigurationSource({_underlyingConfigurationSourceType})")]
+internal sealed class CachedConfigurationSource : IConfigurationSource
+{
+    private readonly object _lockObject = new object();
+    private readonly IConfigurationSource _underlyingConfigurationSource;
+    private readonly string _underlyingConfigurationSourceType;
+    private volatile IConfigurationProvider? _configurationProvider;
+
+    public CachedConfigurationSource(IConfigurationSource underlyingConfigurationSource)
+    {
+        this._underlyingConfigurationSource = underlyingConfigurationSource ?? throw new ArgumentNullException(nameof(underlyingConfigurationSource));
+        this._underlyingConfigurationSourceType = this._underlyingConfigurationSource.GetType().Name;
+    }
+
+    public IConfigurationProvider Build(IConfigurationBuilder builder)
+    {
+        if (this._configurationProvider != null)
+        {
+            return this._configurationProvider;
+        }
+
+        lock (this._lockObject)
+        {
+            if (this._configurationProvider != null)
+            {
+                return this._configurationProvider;
+            }
+
+            this._configurationProvider = this._underlyingConfigurationSource.Build(builder);
+        }
+
+        return this._configurationProvider;
+    }
+}

src/GSoft.Extensions.Configuration.Substitution/ChainedSubstitutedConfigurationProvider.cs

@@ -1,24 +1,24 @@
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Primitives;
 
 namespace GSoft.Extensions.Configuration.Substitution;
 
-internal sealed class ChainedSubstitutedConfigurationProvider : ConfigurationProvider
+internal sealed class ChainedSubstitutedConfigurationProvider : IConfigurationProvider
 {
+    private readonly IConfiguration _configuration;
     private readonly bool _eagerValidation;
 
-    public ChainedSubstitutedConfigurationProvider(IConfigurationRoot configuration, bool eagerValidation)
+    public ChainedSubstitutedConfigurationProvider(IConfiguration configuration, bool eagerValidation)
     {
-        this.Configuration = configuration;
+        this._configuration = configuration;
         this._eagerValidation = eagerValidation;
     }
 
-    public IConfigurationRoot Configuration { get; }
-
-    public override bool TryGet(string key, out string value)
+    public bool TryGet(string key, out string value)
     {
-        var substituted = ConfigurationSubstitutor.GetSubstituted(this.Configuration, key);
+        var substituted = ConfigurationSubstitutor.GetSubstituted(this._configuration, key);
         if (substituted == null)
         {
             value = string.Empty;
@@ -29,9 +29,14 @@ public override bool TryGet(string key, out string value)
         return true;
     }
 
-    public override void Set(string key, string value) => this.Configuration[key] = value;
+    public void Set(string key, string value) => this._configuration[key] = value;
+
+    public IChangeToken GetReloadToken()
+    {
+        return this._configuration.GetReloadToken();
+    }
 
-    public override void Load()
+    public void Load()
     {
         if (this._eagerValidation)
         {
@@ -41,18 +46,17 @@ public override void Load()
 
     private void EnsureAllKeysAreSubstituted()
     {
-        foreach (var kvp in this.Configuration.AsEnumerable())
+        foreach (var kvp in this._configuration.AsEnumerable())
         {
             // This loop goes through the entire configuration (even nested sections).
             // Reading each individual value triggers the substitution process and it will throw if a referenced key is unresolved.
             _ = kvp.Value;
         }
     }
 
-    public override IEnumerable<string> GetChildKeys(IEnumerable<string> earlierKeys, string? parentPath)
+    public IEnumerable<string> GetChildKeys(IEnumerable<string> earlierKeys, string? parentPath)
     {
-        IConfiguration config = this.Configuration;
-        var section = parentPath == null ? config : config.GetSection(parentPath);
+        var section = parentPath == null ? this._configuration : this._configuration.GetSection(parentPath);
         var keys = section.GetChildren().Select(c => c.Key);
         return keys.Concat(earlierKeys).OrderBy(k => k, ConfigurationKeyComparer.Instance).ToArray();
     }

src/GSoft.Extensions.Configuration.Substitution/ChainedSubstitutedConfigurationSource.cs

@@ -4,22 +4,20 @@ namespace GSoft.Extensions.Configuration.Substitution;
 
 internal sealed class ChainedSubstitutedConfigurationSource : IConfigurationSource
 {
-    private readonly IConfigurationSource[] _configurationSources;
     private readonly bool _eagerValidation;
 
-    public ChainedSubstitutedConfigurationSource(IConfigurationSource[] configurationSources, bool eagerValidation)
+    public ChainedSubstitutedConfigurationSource(bool eagerValidation)
     {
-        this._configurationSources = configurationSources;
         this._eagerValidation = eagerValidation;
     }
 
     public IConfigurationProvider Build(IConfigurationBuilder builder)
     {
         var configurationBuilder = new ConfigurationBuilder();
 
-        foreach (var configurationSource in this._configurationSources)
+        for (var i = 0; i < builder.Sources.Count && builder.Sources[i] is not ChainedSubstitutedConfigurationSource; i++)
         {
-            configurationBuilder.Add(configurationSource);
+            configurationBuilder.Add(builder.Sources[i]);
         }
 
         return new ChainedSubstitutedConfigurationProvider(configurationBuilder.Build(), this._eagerValidation);

src/GSoft.Extensions.Configuration.Substitution/ConfigurationSubstitutorBuilderExtensions.cs

@@ -1,4 +1,3 @@
-using System.Linq;
 using GSoft.Extensions.Configuration.Substitution;
 
 // ReSharper disable once CheckNamespace
@@ -17,8 +16,15 @@ public static class ConfigurationSubstitutorBuilderExtensions
     /// <returns>The <see cref="IConfigurationBuilder"/>.</returns>
     public static IConfigurationBuilder AddSubstitution(this IConfigurationBuilder configurationBuilder, bool eagerValidation = false)
     {
-        // Filtering the sources prevents infinite recursive loop where several instances of our configuration source type would wrap each other
-        var configurationSources = configurationBuilder.Sources.Where(x => x is not ChainedSubstitutedConfigurationSource).ToArray();
-        return configurationBuilder.Add(new ChainedSubstitutedConfigurationSource(configurationSources, eagerValidation));
+        for (var i = 0; i < configurationBuilder.Sources.Count; i++)
+        {
+            var configurationSource = configurationBuilder.Sources[i];
+            if (configurationSource is not CachedConfigurationSource)
+            {
+                configurationBuilder.Sources[i] = new CachedConfigurationSource(configurationSource);
+            }
+        }
+
+        return configurationBuilder.Add(new ChainedSubstitutedConfigurationSource(eagerValidation));
     }
 }

src/GSoft.Extensions.Configuration.Substitution/GSoft.Extensions.Configuration.Substitution.csproj

@@ -14,7 +14,6 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="6.0.0" />
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="6.0.0" />
   </ItemGroup>
 
   <ItemGroup>