Introduced Fusion Configuration Rewriter (#6311)

Author: michaelstaib

src/HotChocolate/Fusion/src/Core/Configuration/ConfigurationRewriter.cs

@@ -0,0 +1,123 @@
+using HotChocolate.Fusion.Metadata;
+using HotChocolate.Language;
+
+namespace HotChocolate.Fusion.Configuration;
+
+/// <summary>
+/// This base class allows to rewrite the gateway configuration before it is applied.
+/// </summary>
+public abstract class ConfigurationRewriter : IConfigurationRewriter
+{
+    /// <summary>
+    /// Rewrites the gateway configuration.
+    /// </summary>
+    /// <param name="configuration">
+    /// The gateway configuration.
+    /// </param>
+    /// <param name="cancellationToken">
+    /// The cancellation token.
+    /// </param>
+    /// <returns>
+    /// Returns the rewritten gateway configuration.
+    /// </returns>
+    public virtual async ValueTask<DocumentNode> RewriteAsync(
+        DocumentNode configuration,
+        CancellationToken cancellationToken = default)
+    {
+        if (configuration == null)
+        {
+            throw new ArgumentNullException(nameof(configuration));
+        }
+
+        var config = FusionGraphConfiguration.Load(configuration);
+
+        SchemaDefinitionNode? schemaDefinitionNode = null;
+        List<DirectiveNode>? schemaDirectives = null;
+
+        foreach (var client in config.HttpClients)
+        {
+            var rewritten = await RewriteAsync(client, cancellationToken).ConfigureAwait(false);;
+
+            if (!ReferenceEquals(rewritten, client))
+            {
+                var arguments = new List<ArgumentNode>();
+                arguments.Add(new ArgumentNode(FusionDirectiveArgumentNames.ClientNameArg, rewritten.ClientName));
+                arguments.Add(new ArgumentNode(FusionDirectiveArgumentNames.SubgraphArg, rewritten.SubgraphName));
+                arguments.Add(new ArgumentNode(FusionDirectiveArgumentNames.BaseAddressArg, rewritten.EndpointUri.ToString()));
+                Replace(client.SyntaxNode!, client.SyntaxNode!.WithArguments(arguments));
+            }
+        }
+
+        foreach (var client in config.WebSocketClients)
+        {
+            var rewritten = await RewriteAsync(client, cancellationToken).ConfigureAwait(false);
+
+            if (!ReferenceEquals(rewritten, client))
+            {
+                var arguments = new List<ArgumentNode>();
+                arguments.Add(new ArgumentNode(FusionDirectiveArgumentNames.ClientNameArg, rewritten.ClientName));
+                arguments.Add(new ArgumentNode(FusionDirectiveArgumentNames.SubgraphArg, rewritten.SubgraphName));
+                arguments.Add(new ArgumentNode(FusionDirectiveArgumentNames.BaseAddressArg, rewritten.EndpointUri.ToString()));
+                Replace(client.SyntaxNode!, client.SyntaxNode!.WithArguments(arguments));
+            }
+        }
+
+        return configuration;
+
+        void Replace(DirectiveNode currentDirective, DirectiveNode newDirective)
+        {
+            if (schemaDirectives is null)
+            {
+                if (schemaDefinitionNode is null)
+                {
+                    schemaDefinitionNode = configuration.Definitions.OfType<SchemaDefinitionNode>().First();
+                }
+
+                var definitions = configuration.Definitions.ToList();
+                schemaDirectives = schemaDefinitionNode.Directives.ToList();
+
+                var definitionIndex = definitions.IndexOf(schemaDefinitionNode);
+                schemaDefinitionNode = schemaDefinitionNode.WithDirectives(schemaDirectives);
+                definitions[definitionIndex] = schemaDefinitionNode;
+                configuration = configuration.WithDefinitions(definitions);
+            }
+
+            var index = schemaDirectives.IndexOf(currentDirective);
+            schemaDirectives[index] = newDirective;
+        }
+    }
+
+    /// <summary>
+    /// Rewrites the HTTP client configuration of a subgraph.
+    /// </summary>
+    /// <param name="configuration">
+    /// The HTTP client configuration.
+    /// </param>
+    /// <param name="cancellationToken">
+    /// The cancellation token.
+    /// </param>
+    /// <returns>
+    /// Returns the rewritten HTTP client configuration.
+    /// </returns>
+    protected virtual ValueTask<HttpClientConfiguration> RewriteAsync(
+        HttpClientConfiguration configuration,
+        CancellationToken cancellationToken)
+        => new(configuration);
+
+    /// <summary>
+    /// Rewrites the WebSocket client configuration of a subgraph.
+    /// </summary>
+    /// <param name="configuration">
+    /// The WebSocket client configuration.
+    /// </param>
+    /// <param name="cancellationToken">
+    /// The cancellation token.
+    /// </param>
+    /// <returns>
+    /// Returns the rewritten WebSocket client configuration.
+    /// </returns>
+    protected virtual ValueTask<WebSocketClientConfiguration> RewriteAsync(
+        WebSocketClientConfiguration configuration,
+        CancellationToken cancellationToken)
+        => new(configuration);
+}

src/HotChocolate/Fusion/src/Core/Configuration/IConfigurationRewriter.cs

@@ -0,0 +1,25 @@
+using HotChocolate.Language;
+
+namespace HotChocolate.Fusion.Configuration;
+
+/// <summary>
+/// This interface allows to rewrite the gateway configuration before it is applied.
+/// </summary>
+public interface IConfigurationRewriter
+{
+    /// <summary>
+    /// Rewrites the gateway configuration.
+    /// </summary>
+    /// <param name="configuration">
+    /// The gateway configuration.
+    /// </param>
+    /// <param name="cancellationToken">
+    /// The cancellation token.
+    /// </param>
+    /// <returns>
+    /// Returns the rewritten gateway configuration.
+    /// </returns>
+    ValueTask<DocumentNode> RewriteAsync(
+        DocumentNode configuration,
+        CancellationToken cancellationToken = default);
+}

src/HotChocolate/Fusion/src/Core/DependencyInjection/GatewayConfigurationContext.cs

@@ -20,9 +20,7 @@ public GatewayConfigurationFileObserver(string filename)
     }
 
     public IDisposable Subscribe(IObserver<GatewayConfiguration> observer)
-    {
-        return new FileConfigurationSession(observer, _filename);
-    }
+        => new FileConfigurationSession(observer, _filename);
 
     private sealed class FileConfigurationSession : IDisposable
     {

src/HotChocolate/Fusion/src/Core/DependencyInjection/GatewayConfigurationFileObserver.cs

@@ -1,18 +1,32 @@
 using HotChocolate;
 using HotChocolate.Execution.Configuration;
 using HotChocolate.Fusion;
+using HotChocolate.Fusion.Configuration;
 using HotChocolate.Fusion.Metadata;
 using HotChocolate.Language;
+using HotChocolate.Utilities;
+using static System.Threading.Tasks.TaskCreationOptions;
 
 namespace Microsoft.Extensions.DependencyInjection;
 
 internal sealed class GatewayConfigurationTypeModule : TypeModule
 {
-    private readonly TaskCompletionSource _ready = new(TaskCreationOptions.RunContinuationsAsynchronously);
+    private readonly IEnumerable<IConfigurationRewriter> _configurationRewriters;
+    private readonly TaskCompletionSource _ready = new(RunContinuationsAsynchronously);
     private DocumentNode? _configuration;
 
-    public GatewayConfigurationTypeModule(IObservable<GatewayConfiguration> configuration)
+    public GatewayConfigurationTypeModule(
+        IObservable<GatewayConfiguration> configuration,
+        IEnumerable<IConfigurationRewriter> configurationRewriters)
     {
+        if (configuration == null)
+        {
+            throw new ArgumentNullException(nameof(configuration));
+        }
+
+        _configurationRewriters = configurationRewriters ??
+            throw new ArgumentNullException(nameof(configurationRewriters));
+
         configuration.Subscribe(
             config =>
             {
@@ -24,7 +38,9 @@ public GatewayConfigurationTypeModule(IObservable<GatewayConfiguration> configur
             () => _ready.TrySetCanceled());
     }
 
-    internal override async ValueTask ConfigureAsync(ConfigurationContext context, CancellationToken cancellationToken)
+    internal override async ValueTask ConfigureAsync(
+        ConfigurationContext context,
+        CancellationToken cancellationToken)
     {
         await _ready.Task.WaitAsync(cancellationToken).ConfigureAwait(false);
 
@@ -33,11 +49,24 @@ internal override async ValueTask ConfigureAsync(ConfigurationContext context, C
             throw ThrowHelper.UnableToLoadConfiguration();
         }
 
+        var config = _configuration;
+
+        foreach (var rewriter in _configurationRewriters)
+        {
+            config = await rewriter.RewriteAsync(config, cancellationToken)
+                .ConfigureAwait(false);
+        }
+
+        ApplyConfiguration(context.SchemaBuilder, config);
+    }
+
+    private void ApplyConfiguration(ISchemaBuilder schemaBuilder, DocumentNode config)
+    {
         var rewriter = new FusionGraphConfigurationToSchemaRewriter();
-        var fusionGraphConfig = FusionGraphConfiguration.Load(_configuration);
-        var schemaDoc = rewriter.Rewrite(_configuration);
+        var fusionGraphConfig = FusionGraphConfiguration.Load(config);
+        var schemaDoc = rewriter.Rewrite(config);
 
-        context.SchemaBuilder
+        schemaBuilder
             .AddDocument(schemaDoc)
             .SetFusionGraphConfig(fusionGraphConfig);
     }

src/HotChocolate/Fusion/src/Core/DependencyInjection/GatewayConfigurationResolver.cs

@@ -50,4 +50,5 @@
     <PackageReference Include="System.Reactive" Version="5.0.0" />
   </ItemGroup>
 
+
 </Project>

src/HotChocolate/Fusion/src/Core/DependencyInjection/GatewayConfigurationTypeModule.cs

@@ -180,7 +180,7 @@ private HttpClientConfiguration ReadHttpClientConfig(
             name = subgraph;
         }
 
-        return new HttpClientConfiguration(name, subgraph, new Uri(baseAddress));
+        return new HttpClientConfiguration(name, subgraph, new Uri(baseAddress), directiveNode);
 
         static void OptionalArgs(HashSet<string> assert)
         {
@@ -239,7 +239,7 @@ private WebSocketClientConfiguration ReadWebSocketClientConfig(
             name = subgraph;
         }
 
-        return new WebSocketClientConfiguration(name, subgraph, new Uri(baseAddress));
+        return new WebSocketClientConfiguration(name, subgraph, new Uri(baseAddress), directiveNode);
 
         static void OptionalArgs(HashSet<string> assert)
         {

src/HotChocolate/Fusion/src/Core/HotChocolate.Fusion.csproj

@@ -1,9 +1,11 @@
+using HotChocolate.Language;
+
 namespace HotChocolate.Fusion.Metadata;
 
 /// <summary>
 /// Represents the configuration of a GraphQL over HTTP client.
 /// </summary>
-public sealed class HttpClientConfiguration : IGraphQLClientConfiguration
+public sealed record HttpClientConfiguration : IGraphQLClientConfiguration
 {
     /// <summary>
     /// Initializes a new instance of <see cref="HttpClientConfiguration"/>.
@@ -17,25 +19,38 @@ public sealed class HttpClientConfiguration : IGraphQLClientConfiguration
     /// <param name="endpointUri">
     /// The base address of the GraphQL over HTTP endpoint.
     /// </param>
-    public HttpClientConfiguration(string clientName, string subgraphName, Uri endpointUri)
+    /// <param name="syntaxNode">
+    /// The configuration syntax node.
+    /// </param>
+    public HttpClientConfiguration(
+        string clientName,
+        string subgraphName,
+        Uri endpointUri,
+        DirectiveNode? syntaxNode = null)
     {
         ClientName = clientName;
         SubgraphName = subgraphName;
         EndpointUri = endpointUri;
+        SyntaxNode = syntaxNode;
     }
 
     /// <summary>
     /// Gets the name of the client.
     /// </summary>
-    public string ClientName { get; }
+    public string ClientName { get; init; }
 
     /// <summary>
     /// Gets the name of the subgraph that the client is connecting to.
     /// </summary>
-    public string SubgraphName { get; }
+    public string SubgraphName { get; init; }
 
     /// <summary>
     /// Gets the URI of the GraphQL over HTTP endpoint.
     /// </summary>
-    public Uri EndpointUri { get; }
+    public Uri EndpointUri { get; init; }
+
+    /// <summary>
+    /// Gets the configuration syntax node.
+    /// </summary>
+    public DirectiveNode? SyntaxNode { get; init; }
 }