fix(dontet): excessive overrides generated (#3355)

A mis-understanding of the jsii specification early on was carried over
in the .NET code generators until now, which caused all methods and
properties that are overrides (of other JS implementations) to result in
jsii overrides being registered by the runtime.

This behavior caused unnecessary round-trips between the .NET CLR and
the node sidekick process, which affected the performance of .NET
bindings (unnecessary round-trips with JSON encoding aren't free), and
had a tendency to hit obscure edge case bugs in the jsii kernel's Ser/De
behavior.

This PR removes all `isOverride: true` declarations from generated .NET
code and neutralizes the behavior of specifying it to be true.
User-defined overrides (.NET code overriding JS code) continue to work
as they previously did (the `isOverride` attribute should simply not
have existed, ever).



---

By submitting this pull request, I confirm that my contribution is made under the terms of the [Apache 2.0 license].

[Apache 2.0 license]: https://www.apache.org/licenses/LICENSE-2.0

packages/@jsii/dotnet-runtime/src/Amazon.JSII.Runtime/Deputy/DeputyBase.cs

@@ -76,7 +76,7 @@ IEnumerable<Override> GetMethodOverrides()
                     var inheritedAttribute = method.GetAttribute<JsiiMethodAttribute>();
                     var uninheritedAttribute = method.GetAttribute<JsiiMethodAttribute>(false);
 
-                    if ((inheritedAttribute != null && uninheritedAttribute == null) || uninheritedAttribute?.IsOverride == true)
+                    if (inheritedAttribute != null && uninheritedAttribute == null)
                     {
                         yield return new Override(method: (inheritedAttribute ?? uninheritedAttribute)!.Name);
                     }
@@ -93,7 +93,7 @@ IEnumerable<Override> GetPropertyOverrides()
                     var inheritedAttribute = property.GetAttribute<JsiiPropertyAttribute>();
                     var uninheritedAttribute = property.GetAttribute<JsiiPropertyAttribute>(false);
 
-                    if ((inheritedAttribute != null && uninheritedAttribute == null) || uninheritedAttribute?.IsOverride == true)
+                    if (inheritedAttribute != null && uninheritedAttribute == null)
                     {
                         yield return new Override(property: (inheritedAttribute ?? uninheritedAttribute)!.Name);
                     }

packages/@jsii/dotnet-runtime/src/Amazon.JSII.Runtime/Deputy/JsiiMethodAttribute.cs

@@ -12,6 +12,7 @@ public sealed class JsiiMethodAttribute : Attribute
             string? returnsJson = null,
             string? parametersJson = null,
             bool isAsync = false,
+            // Unused, retained for backwards-compatibility
             bool isOverride = false)
         {
             Name = name ?? throw new ArgumentNullException(nameof(name));
@@ -23,7 +24,6 @@ public sealed class JsiiMethodAttribute : Attribute
                 : JsonConvert.DeserializeObject<Parameter[]>(parametersJson)
                   ?? throw new ArgumentException("Invalid JSON descriptor", nameof(parametersJson));
             IsAsync = isAsync;
-            IsOverride = isOverride;
         }
 
         public string Name { get; }
@@ -34,7 +34,5 @@ public sealed class JsiiMethodAttribute : Attribute
 
 
         public bool IsAsync { get; }
-
-        public bool IsOverride { get; }
     }
-}
+}

packages/@jsii/dotnet-runtime/src/Amazon.JSII.Runtime/Deputy/JsiiPropertyAttribute.cs

@@ -7,22 +7,24 @@ namespace Amazon.JSII.Runtime.Deputy
     [AttributeUsage(AttributeTargets.Property)]
     public sealed class JsiiPropertyAttribute : Attribute, IOptionalValue
     {
-        public JsiiPropertyAttribute(string name, string typeJson, bool isOptional = false, bool isOverride = false)
+        public JsiiPropertyAttribute(
+            string name,
+            string typeJson,
+            bool isOptional = false,
+            // Unused, retained for backwards-compatibility
+            bool isOverride = false)
         {
             Name = name ?? throw new ArgumentNullException(nameof(name));
             Type = JsonConvert.DeserializeObject<TypeReference>(typeJson ??
                                                                 throw new ArgumentNullException(nameof(typeJson)))
                    ?? throw new ArgumentException("Invalid JSON descriptor", nameof(typeJson));
             IsOptional = isOptional;
-            IsOverride = isOverride;
         }
 
         public string Name { get; }
 
         public TypeReference Type { get; }
 
         public bool IsOptional { get; }
-
-        public bool IsOverride { get; }
     }
-}
+}

packages/jsii-pacmak/lib/targets/dotnet/dotnetgenerator.ts

@@ -942,7 +942,7 @@ export class DotNetGenerator extends Generator {
     if (prop.optional) {
       this.code.line('[JsiiOptional]');
     }
-    this.dotnetRuntimeGenerator.emitAttributesForProperty(prop, datatype);
+    this.dotnetRuntimeGenerator.emitAttributesForProperty(prop);
 
     let isOverrideKeyWord = '';
     let isVirtualKeyWord = '';

packages/jsii-pacmak/lib/targets/dotnet/dotnetruntimegenerator.ts

@@ -78,8 +78,6 @@ export class DotNetRuntimeGenerator {
     cls: spec.ClassType | spec.InterfaceType,
     method: spec.Method /*, emitForProxyOrDatatype: boolean = false*/,
   ): void {
-    const isOverride =
-      spec.isClassType(cls) && method.overrides ? ', isOverride: true' : '';
     const isAsync =
       spec.isClassType(cls) && method.async ? ', isAsync: true' : '';
     const parametersJson = method.parameters
@@ -92,28 +90,23 @@ export class DotNetRuntimeGenerator {
           .replace(/"/g, '\\"')
           .replace(/\\{2}"/g, 'test')}"`
       : '';
-    const jsiiAttribute = `[JsiiMethod(name: "${method.name}"${returnsJson}${parametersJson}${isAsync}${isOverride})]`;
+    const jsiiAttribute = `[JsiiMethod(name: "${method.name}"${returnsJson}${parametersJson}${isAsync})]`;
     this.code.line(jsiiAttribute);
     this.emitDeprecatedAttributeIfNecessary(method);
   }
 
   /**
    * Emits the proper jsii .NET attribute for a property
    *
-   * Ex: [JsiiProperty(name: "foo", typeJson: "{\"fqn\":\"@scope/jsii-calc-base-of-base.Very\"}", isOptional: true, isOverride: true)]
+   * Ex: [JsiiProperty(name: "foo", typeJson: "{\"fqn\":\"@scope/jsii-calc-base-of-base.Very\"}", isOptional: true)]
    */
-  public emitAttributesForProperty(
-    prop: spec.Property,
-    datatype = false,
-  ): void {
-    // If we are on a datatype then we want the property to override in Jsii
-    const isJsiiOverride = datatype ? ', isOverride: true' : '';
+  public emitAttributesForProperty(prop: spec.Property): void {
     const isOptionalJsii = prop.optional ? ', isOptional: true' : '';
     const jsiiAttribute =
       `[JsiiProperty(name: "${prop.name}", ` +
       `typeJson: "${JSON.stringify(prop.type)
         .replace(/"/g, '\\"')
-        .replace(/\\{2}"/g, 'test')}"${isOptionalJsii}${isJsiiOverride})]`;
+        .replace(/\\{2}"/g, 'test')}"${isOptionalJsii})]`;
     this.code.line(jsiiAttribute);
     this.emitDeprecatedAttributeIfNecessary(prop);
   }