[Fusion] Properly handle partial schema-settings.json and configuration in code (#9766)

Author: tobias-tengler

src/HotChocolate/Fusion/src/Fusion.Execution/Execution/FusionRequestExecutorManager.cs

@@ -863,18 +863,20 @@ private SourceSchemaClientConfigurations CreateClientConfigurations(
             JsonElement settings)
         {
             var configurations = new List<ISourceSchemaClientConfiguration>();
+            List<string>? unclaimedSourceSchemas = null;
 
             if (settings.TryGetProperty("sourceSchemas", out var sourceSchemas))
             {
                 foreach (var sourceSchema in sourceSchemas.EnumerateObject())
                 {
-                    if (!TryClaimSourceSchema(schema, sourceSchema, setup, out var sourceConfigurations))
+                    if (TryClaimSourceSchema(schema, sourceSchema, setup, out var sourceConfigurations))
                     {
-                        throw new InvalidOperationException(
-                            $"No parser claimed source schema '{sourceSchema.Name}'.");
+                        configurations.AddRange(sourceConfigurations);
+                    }
+                    else
+                    {
+                        (unclaimedSourceSchemas ??= []).Add(sourceSchema.Name);
                     }
-
-                    configurations.AddRange(sourceConfigurations);
                 }
             }
 
@@ -883,6 +885,25 @@ private SourceSchemaClientConfigurations CreateClientConfigurations(
                 configurations.Add(configure.Invoke(applicationServices));
             }
 
+            if (unclaimedSourceSchemas is not null)
+            {
+                var configuredNames = new HashSet<string>(StringComparer.Ordinal);
+                foreach (var configuration in configurations)
+                {
+                    configuredNames.Add(configuration.Name);
+                }
+
+                foreach (var name in unclaimedSourceSchemas)
+                {
+                    if (!configuredNames.Contains(name))
+                    {
+                        throw new InvalidOperationException(
+                            $"The source schema configuration of '{name}' could not be parsed "
+                            + "and no client configuration was registered for it in code.");
+                    }
+                }
+            }
+
             // Register configurations that need post-Seal projection. The
             // per-type completions (Lookup.FieldType, FieldRequirements.Requirements)
             // were registered earlier during type completion; appending here

src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Configuration/DefaultGraphQLClientConfigurationParserTests.cs

@@ -387,7 +387,55 @@ public async Task CreateClientConfigurations_Should_Throw_When_No_Parser_Claims_
 
         // assert
         var exception = await Assert.ThrowsAsync<InvalidOperationException>(Act);
-        Assert.Equal("No parser claimed source schema 'a'.", exception.Message);
+        Assert.Equal(
+            "The source schema configuration of 'a' could not be parsed and no client "
+            + "configuration was registered for it in code.",
+            exception.Message);
+    }
+
+    [Fact]
+    public async Task CreateClientConfigurations_Should_Not_Throw_When_Modifier_Provides_Missing_Configuration()
+    {
+        // arrange
+        // settings carry only a non-http transport, but a client configuration for "a"
+        // is supplied in code via AddHttpClientConfiguration.
+        var config = CreateConfigurationWithSettings(
+            """
+            {
+                "sourceSchemas": {
+                    "a": {
+                        "transports": {
+                            "xyz": { "url": "xyz://localhost" }
+                        }
+                    }
+                }
+            }
+            """);
+
+        var configProvider = new TestFusionConfigurationProvider(config);
+
+        var services =
+            new ServiceCollection()
+                .AddGraphQLGateway()
+                .AddConfigurationProvider(_ => configProvider)
+                .AddHttpClientConfiguration(
+                    new HttpSourceSchemaClientConfiguration(
+                        name: "a",
+                        httpClientName: HttpSourceSchemaClientConfiguration.DefaultClientName,
+                        baseAddress: new Uri("http://localhost:5000/graphql")))
+                .Services
+                .BuildServiceProvider();
+
+        var manager = services.GetRequiredService<FusionRequestExecutorManager>();
+
+        // act
+        var executor = await manager.GetExecutorAsync();
+
+        // assert
+        var clientConfigs = executor.Schema.Features.GetRequired<SourceSchemaClientConfigurations>();
+        Assert.True(clientConfigs.TryGet("a", OperationType.Query, out var queryConfig));
+        var http = Assert.IsType<HttpSourceSchemaClientConfiguration>(queryConfig);
+        Assert.Equal(new Uri("http://localhost:5000/graphql"), http.BaseAddress);
     }
 
     [Fact]