[Mgmt Generator] Multi-scope resource generates duplicate GetXxxResource factory methods (CS0111)

[mzhongl524]

Bug Description

The MPG generator (Azure Management Plane Generator) produces duplicate identical GetXxxResource factory methods when a TypeSpec spec defines a multi-scope resource using Legacy.ExtensionOperations with multiple interfaces. This causes CS0111 ("Type already defines a member with the same parameter types") compilation errors.

Spec Structure

Repo: Azure/azure-rest-api-specs
Path: specification/kubernetesconfiguration/resource-manager/Microsoft.KubernetesConfiguration/extensionTypes/
Commit: 8d0a948edb8a860ea00768533210f98634a0870e

ExtensionType.tsp

Defines the ExtensionType resource model with 2 interfaces at different scopes:

// Scope 1: Subscription/Location
// Path: /subscriptions/{subscriptionId}/providers/Microsoft.KubernetesConfiguration/locations/{location}/extensionTypes/{extensionTypeName}
alias ExtensionTypeOps = Azure.ResourceManager.Legacy.ExtensionOperations<
  { ...ApiVersionParameter; ...SubscriptionIdParameter; @path @segment("providers") @key providerNamespace: "Microsoft.KubernetesConfiguration"; ...LocationParameter; },
  {},
  { @path @segment("extensionTypes") @key @pattern("^[a-zA-Z][a-zA-Z0-9-_]*$") extensionTypeName: string; }
>;
@armResourceOperations(#{ omitTags: true })
interface ExtensionTypes { ... }

// Scope 2: ResourceGroup/Cluster
// Path: /subscriptions/{subscriptionId}/resourceGroups/{rg}/providers/{clusterRp}/{clusterResourceName}/{clusterName}/providers/Microsoft.KubernetesConfiguration/extensionTypes/{extensionTypeName}
alias ExtensionTypeOperationGroupOps = Azure.ResourceManager.Legacy.ExtensionOperations<
  { ...ApiVersionParameter; ...SubscriptionIdParameter; ...ResourceGroupParameter; @path @segment("providers") @key clusterRp: string; @key @path clusterResourceName: string; @key @path clusterName: string; },
  { ...Extension.ExtensionProviderNamespace<ExtensionType>; ...ParentKeysOf<ExtensionType>; },
  { ...Extension.ExtensionProviderNamespace<ExtensionType>; ...KeysOf<ExtensionType>; }
>;
@armResourceOperations(#{ omitTags: true })
interface ExtensionTypeOperationGroup { ... }

ExtensionTypeVersionForReleaseTrain.tsp

Defines a child resource @parentResource(ExtensionType) with another 2 interfaces at different scopes:

interface ExtensionTypeVersionForReleaseTrains { ... }          // Location scope
interface ExtensionTypeVersionForReleaseTrainOperationGroup { ... }  // Cluster scope

back-compatible.tsp

Uses @@clientLocation to consolidate operations:

@@clientLocation(ExtensionTypeOperationGroup.get, ExtensionTypes);
@@clientLocation(ExtensionTypeOperationGroup.list, ExtensionTypes);
@@clientLocation(ExtensionTypeVersionForReleaseTrains.getVersion, ExtensionTypes);
@@clientLocation(ExtensionTypeVersionForReleaseTrains.listVersions, ExtensionTypes);
@@clientLocation(ExtensionTypeVersionForReleaseTrainOperationGroup.clusterGetVersion, ExtensionTypes);
@@clientLocation(ExtensionTypeVersionForReleaseTrainOperationGroup.clusterListVersions, ExtensionTypes);

But @@clientLocation only moves operations (Read/List), not the resource factory methods.

Swagger (Generated OpenAPI)

The swagger produces 4 operation groups that all reference the same ExtensionType schema:

• ExtensionTypes_LocationGet / ExtensionTypes_LocationList (subscription/location scope)
• ExtensionTypeOperationGroup_Get / ExtensionTypeOperationGroup_List (cluster scope)
• ExtensionTypeVersionForReleaseTrains_GetVersion / ..._ListVersions (location scope)
• ExtensionTypeVersionForReleaseTrainOperationGroup_ClusterGetVersion / ..._ClusterListVersions (cluster scope)

All operation groups share the same resource model ExtensionType, which maps to the single C# class ExtensionTypeInterfaceResource.

Generated Code (Bug)

After running dotnet build /t:GenerateCode, the generator produces 4 identical copies of each factory method:

In KubernetesConfigurationExtensionTypesExtensions.cs:

// Copy 1 (from ExtensionTypes interface)
public static ExtensionTypeInterfaceResource GetExtensionTypeInterfaceResource(this ArmClient client, ResourceIdentifier id) { ... }
// Copy 2 (from ExtensionTypeOperationGroup interface)
public static ExtensionTypeInterfaceResource GetExtensionTypeInterfaceResource(this ArmClient client, ResourceIdentifier id) { ... }
// Copy 3 (from ExtensionTypeVersionForReleaseTrains interface)
public static ExtensionTypeInterfaceResource GetExtensionTypeInterfaceResource(this ArmClient client, ResourceIdentifier id) { ... }
// Copy 4 (from ExtensionTypeVersionForReleaseTrainOperationGroup interface)
public static ExtensionTypeInterfaceResource GetExtensionTypeInterfaceResource(this ArmClient client, ResourceIdentifier id) { ... }

In MockableKubernetesConfigurationExtensionTypesArmClient.cs:

// Same 4 identical copies of:
public virtual ExtensionTypeInterfaceResource GetExtensionTypeInterfaceResource(ResourceIdentifier id) { ... }

Expected Behavior

The generator should deduplicate GetXxxResource factory methods. Regardless of how many interfaces/scopes reference the same resource model, only one copy of each factory method should be generated.

Current Workaround

SDK-side workaround using [CodeGenSuppress] + custom partial class implementation:

[CodeGenSuppress("GetExtensionTypeInterfaceResource", typeof(ArmClient), typeof(ResourceIdentifier))]
public static partial class KubernetesConfigurationExtensionTypesExtensions
{
    public static ExtensionTypeInterfaceResource GetExtensionTypeInterfaceResource(this ArmClient client, ResourceIdentifier id) { ... }
}

[CodeGenSuppress("GetExtensionTypeInterfaceResource", typeof(ResourceIdentifier))]
public partial class MockableKubernetesConfigurationExtensionTypesArmClient
{
    public virtual ExtensionTypeInterfaceResource GetExtensionTypeInterfaceResource(ResourceIdentifier id) { ... }
}

Affected Component

eng/packages/http-client-csharp-mgmt — resource factory method generation logic. The deduplication should likely happen when collecting resource factory methods across multiple interfaces/scopes in resolve-arm-resources-converter.ts or the extension method generation code.

[mzhongl524]

Additional Bug: Collection Constructor Parameter Mismatch

Same root cause (multi-scope Legacy.ExtensionOperations + @@clientLocation), different symptom:

Problem

The Mockable classes generate GetExtensionTypeInterfaces() methods that pass extra scope parameters to the ExtensionTypeInterfaceCollection constructor, but the generated Collection only has a 2-arg constructor (ArmClient client, ResourceIdentifier id).

MockableSubscriptionResource generates:

public virtual ExtensionTypeInterfaceCollection GetExtensionTypeInterfaces(string location)
{
    return GetCachedClient(client => new ExtensionTypeInterfaceCollection(client, Id, location));
    // 3-arg call, but Collection only has 2-arg ctor
}

MockableResourceGroupResource generates:

public virtual ExtensionTypeInterfaceCollection GetExtensionTypeInterfaces(string clusterRp, string clusterResourceName, string clusterName)
{
    return GetCachedClient(client => new ExtensionTypeInterfaceCollection(client, Id, clusterRp, clusterResourceName, clusterName));
    // 5-arg call, but Collection only has 2-arg ctor
}

Codegen Source

• MockableResourceProvider.cs:254 - correctly generates scope-specific parameters for each parent scope
• ResourceCollectionClientProvider.cs:253-302 - BuildResourceIdentifierConstructor() only generates the base (ArmClient, ResourceIdentifier) constructor; _extraCtorParameters from SecondaryContextualPathParameters is empty for this multi-scope case

Current Workaround

Custom partial class adds the missing constructor overloads (extra params are ignored since operations derive scope info from ResourceIdentifier):

public partial class ExtensionTypeInterfaceCollection
{
    internal ExtensionTypeInterfaceCollection(ArmClient client, ResourceIdentifier id, string location)
        : this(client, id) { }

    internal ExtensionTypeInterfaceCollection(ArmClient client, ResourceIdentifier id, string clusterRp, string clusterResourceName, string clusterName)
        : this(client, id) { }
}