[Fusion] Added structure for post-merge validation (#7969)

Author: glen-84

src/HotChocolate/Fusion-vnext/src/Fusion.Composition/Errors/ErrorHelper.cs

@@ -10,6 +10,9 @@ public static CompositionError SourceSchemaParsingFailed()
     public static CompositionError SourceSchemaValidationFailed()
         => new(ErrorHelper_SourceSchemaValidationFailed);
 
+    public static CompositionError PostMergeValidationFailed()
+        => new(ErrorHelper_PostMergeValidationFailed);
+
     public static CompositionError PreMergeValidationFailed()
         => new(ErrorHelper_PreMergeValidationFailed);
 }

src/HotChocolate/Fusion-vnext/src/Fusion.Composition/Events/Contracts/IEvent.cs

@@ -0,0 +1,3 @@
+namespace HotChocolate.Fusion.Events.Contracts;
+
+internal interface IEvent;

src/HotChocolate/Fusion-vnext/src/Fusion.Composition/Events/IEventHandler.cs renamed to src/HotChocolate/Fusion-vnext/src/Fusion.Composition/Events/Contracts/IEventHandler.cs

@@ -1,4 +1,4 @@
-namespace HotChocolate.Fusion.Events;
+namespace HotChocolate.Fusion.Events.Contracts;
 
 internal interface IEventHandler<in TEvent> where TEvent : IEvent
 {

src/HotChocolate/Fusion-vnext/src/Fusion.Composition/PreMergeValidation/Events.cs renamed to src/HotChocolate/Fusion-vnext/src/Fusion.Composition/Events/GroupEvents.cs

@@ -1,8 +1,8 @@
 using System.Collections.Immutable;
-using HotChocolate.Fusion.Events;
+using HotChocolate.Fusion.Events.Contracts;
 using HotChocolate.Fusion.Info;
 
-namespace HotChocolate.Fusion.PreMergeValidation;
+namespace HotChocolate.Fusion.Events;
 
 internal record EnumTypeGroupEvent(
     string TypeName,

src/HotChocolate/Fusion-vnext/src/Fusion.Composition/Events/IEvent.cs

@@ -1,9 +1,9 @@
 using System.Collections.Immutable;
-using HotChocolate.Fusion.Events;
+using HotChocolate.Fusion.Events.Contracts;
 using HotChocolate.Language;
 using HotChocolate.Skimmed;
 
-namespace HotChocolate.Fusion.SourceSchemaValidation;
+namespace HotChocolate.Fusion.Events;
 
 internal record DirectiveArgumentEvent(
     InputFieldDefinition Argument,
@@ -16,6 +16,19 @@ internal record FieldArgumentEvent(
     INamedTypeDefinition Type,
     SchemaDefinition Schema) : IEvent;
 
+internal record InputFieldEvent(
+    InputFieldDefinition InputField,
+    InputObjectTypeDefinition InputType,
+    SchemaDefinition Schema) : IEvent;
+
+internal record InputTypeEvent(
+    InputObjectTypeDefinition InputType,
+    SchemaDefinition Schema) : IEvent;
+
+internal record InterfaceTypeEvent(
+    InterfaceTypeDefinition InterfaceType,
+    SchemaDefinition Schema) : IEvent;
+
 internal record KeyFieldEvent(
     Directive KeyDirective,
     ComplexTypeDefinition EntityType,
@@ -47,6 +60,10 @@ internal record KeyFieldsInvalidTypeEvent(
     ComplexTypeDefinition EntityType,
     SchemaDefinition Schema) : IEvent;
 
+internal record ObjectTypeEvent(
+    ObjectTypeDefinition ObjectType,
+    SchemaDefinition Schema) : IEvent;
+
 internal record OutputFieldEvent(
     OutputFieldDefinition Field,
     INamedTypeDefinition Type,

src/HotChocolate/Fusion-vnext/src/Fusion.Composition/SourceSchemaValidation/Events.cs renamed to src/HotChocolate/Fusion-vnext/src/Fusion.Composition/Events/SchemaEvents.cs

@@ -1,18 +1,83 @@
 using System.Collections.Immutable;
+using HotChocolate.Fusion.Errors;
+using HotChocolate.Fusion.Events;
+using HotChocolate.Fusion.Events.Contracts;
+using HotChocolate.Fusion.Logging.Contracts;
 using HotChocolate.Fusion.Results;
 using HotChocolate.Skimmed;
 
 namespace HotChocolate.Fusion;
 
-#pragma warning disable CS9113 // Parameter is unread.
 internal sealed class PostMergeValidator(
     SchemaDefinition mergedSchema,
-    ImmutableArray<object> rules)
-#pragma warning restore CS9113 // Parameter is unread.
+    ImmutableArray<object> rules,
+    ImmutableSortedSet<SchemaDefinition> sourceSchemas,
+    ICompositionLog log)
 {
     public CompositionResult Validate()
     {
-        // FIXME: Implement.
-        return CompositionResult.Success();
+        PublishEvents();
+
+        return log.HasErrors
+            ? ErrorHelper.PostMergeValidationFailed()
+            : CompositionResult.Success();
+    }
+
+    private void PublishEvents()
+    {
+        var context = new CompositionContext(sourceSchemas, log);
+
+        PublishEvent(new SchemaEvent(mergedSchema), context);
+
+        foreach (var type in mergedSchema.Types)
+        {
+            switch (type)
+            {
+                case InputObjectTypeDefinition inputType:
+                    PublishEvent(new InputTypeEvent(inputType, mergedSchema), context);
+
+                    foreach (var field in inputType.Fields)
+                    {
+                        PublishEvent(new InputFieldEvent(field, inputType, mergedSchema), context);
+                    }
+
+                    break;
+
+                case InterfaceTypeDefinition interfaceType:
+                    PublishEvent(new InterfaceTypeEvent(interfaceType, mergedSchema), context);
+                    break;
+
+                case ObjectTypeDefinition objectType:
+                    PublishEvent(new ObjectTypeEvent(objectType, mergedSchema), context);
+                    break;
+            }
+
+            if (type is ComplexTypeDefinition complexType)
+            {
+                foreach (var field in complexType.Fields)
+                {
+                    PublishEvent(new OutputFieldEvent(field, complexType, mergedSchema), context);
+
+                    foreach (var argument in field.Arguments)
+                    {
+                        PublishEvent(
+                            new FieldArgumentEvent(argument, field, complexType, mergedSchema),
+                            context);
+                    }
+                }
+            }
+        }
+    }
+
+    private void PublishEvent<TEvent>(TEvent @event, CompositionContext context)
+        where TEvent : IEvent
+    {
+        foreach (var rule in rules)
+        {
+            if (rule is IEventHandler<TEvent> handler)
+            {
+                handler.Handle(@event, context);
+            }
+        }
     }
 }

src/HotChocolate/Fusion-vnext/src/Fusion.Composition/PostMergeValidator.cs

@@ -1,9 +1,10 @@
 using System.Collections.Immutable;
 using HotChocolate.Fusion.Events;
+using HotChocolate.Fusion.Events.Contracts;
 using HotChocolate.Fusion.Extensions;
 using static HotChocolate.Fusion.Logging.LogEntryHelper;
 
-namespace HotChocolate.Fusion.PreMergeValidation.Rules;
+namespace HotChocolate.Fusion.PreMergeValidationRules;
 
 /// <summary>
 /// <para>

src/HotChocolate/Fusion-vnext/src/Fusion.Composition/PreMergeValidation/Rules/EnumValuesMismatchRule.cs renamed to src/HotChocolate/Fusion-vnext/src/Fusion.Composition/PreMergeValidationRules/EnumValuesMismatchRule.cs

@@ -1,10 +1,11 @@
 using System.Collections.Immutable;
 using HotChocolate.Fusion.Events;
+using HotChocolate.Fusion.Events.Contracts;
 using HotChocolate.Fusion.Extensions;
 using HotChocolate.Language;
 using static HotChocolate.Fusion.Logging.LogEntryHelper;
 
-namespace HotChocolate.Fusion.PreMergeValidation.Rules;
+namespace HotChocolate.Fusion.PreMergeValidationRules;
 
 /// <summary>
 /// This rule ensures that arguments on fields marked as <c>@external</c> have default values

src/HotChocolate/Fusion-vnext/src/Fusion.Composition/PreMergeValidation/Rules/ExternalArgumentDefaultMismatchRule.cs renamed to src/HotChocolate/Fusion-vnext/src/Fusion.Composition/PreMergeValidationRules/ExternalArgumentDefaultMismatchRule.cs

@@ -1,9 +1,10 @@
 using System.Collections.Immutable;
 using HotChocolate.Fusion.Events;
+using HotChocolate.Fusion.Events.Contracts;
 using HotChocolate.Fusion.Extensions;
 using static HotChocolate.Fusion.Logging.LogEntryHelper;
 
-namespace HotChocolate.Fusion.PreMergeValidation.Rules;
+namespace HotChocolate.Fusion.PreMergeValidationRules;
 
 /// <summary>
 /// This rule ensures that any field marked as <c>@external</c> in a source schema is actually