[Mgmt CodeGen] Support customizing resource names via @@clientOption resource-name-mappings

[haiyuazhang]

Resolves #59210.

Problem

In the Swagger world,
equest-path-to-resource-name lets users override the generated resource name for path-templated resources (the canonical example being DNS, where …/dnsZones/{zoneName}/{recordType}/{relativeRecordSetName}|Microsoft.Network/dnsZones/A: DnsARecord produces DnsARecord instead of an auto-derived name).

The TypeSpec mgmt emitter already expands a single resource with a dynamic {parentType} segment into one concrete resource per enum value (see expandDynamicParentResourcesInSchema in resource-metadata.ts), but the names are always built as Capitalize(singular(enumValue)) + baseResourceName with no customization knob. The issue asks for that knob.

Approach

Add a generic @@clientOption(model, ""resource-name-mappings"", #{ … }) decorator key. The value is a record mapping the currently generated resourceName (LHS) to the desired resourceName (RHS).

The rename is applied as a pure, name-only, late transformation – after expansion, parent inference, scope assignment, post-processing, and api-version resolution. Nothing downstream in the emitter depends on resourceName for correctness (parent lookup is by resourceModelId + path-prefix, scope by path), so the rename is a safe last step.

Because it's generic (keyed by final generated name + the model), it works uniformly for:

• normal resources (rename the SDK class without renaming the underlying model),
• singleton resources,
• expanded {parentType} resources (the DNS / issue motivation),
  without any special-casing inside the expansion code.

What's in this PR

Commit 1 – emitter feature (eng/packages/http-client-csharp-mgmt/emitter):

• New "resource-name-mappings" key + extractResourceNameMappings and applyResourceNameOverrides helpers in resource-metadata.ts.
• Wired into both code paths just before the final return:
  • resource-detection.ts:buildArmProviderSchema (legacy path)
  • resolve-arm-resources-converter.ts:resolveArmResources (modern resolveArmResources path)
• Diagnostics for unused mapping entries (catches typos / generator-name drift) and for post-rename name collisions.

Commit 2 – end-to-end demonstration on generator/TestProjects/Local/Mgmt-TypeSpec:

• routedoperations.tsp adds the decorator to the existing EventGridPrivateEndpointConnection expandable resource.
• Six generated C# files renamed (EventGridTopicEventGridPrivateEndpointConnection* → EventGridTopicPrivateEndpointConnection*, similarly for Domain).
• Surrounding generated files (parent resources, extensions, context, tspCodeModel.json) updated to reference the new names. dotnet build passes with 0 warnings / 0 errors.

Example usage

``tsp
// One model shared by N expanded resources
@@clientoption(EventGridPrivateEndpointConnection,
""resource-name-mappings"",
#{
EventGridTopicEventGridPrivateEndpointConnection: ""EventGridTopicPrivateEndpointConnection"",
EventGridDomainEventGridPrivateEndpointConnection: ""EventGridDomainPrivateEndpointConnection"",
},
""csharp"");

// Plain resource rename
@@clientoption(RecordSet, ""resource-name-mappings"", #{ RecordSet: ""DnsRecordSet"" }, ""csharp"");
``

Follow-ups (not in this PR)

• Unit tests for applyResourceNameOverrides mirroring the existing resource-name-constraint tests in resource-detection.test.ts (single resource rename, partial expansion override, unused-key diagnostic, collision diagnostic).
• Doc page under eng/packages/http-client-csharp-mgmt/docs listing the supported @@clientOption keys.

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com

[Copilot]

Pull request overview

This PR adds a new TypeSpec @@clientOption key ("resource-name-mappings") to the C# mgmt emitter to allow late-stage, name-only overrides of generated ARM resource wrapper names (including {parentType} expanded resources), and updates the local Mgmt-TypeSpec test project to demonstrate the feature end-to-end.

Changes:

• Added parsing/apply logic for @@clientOption(model, "resource-name-mappings", #{ ... }, "csharp") in the mgmt emitter, wired into both legacy and resolveArmResources code paths.
• Added a TypeSpec usage example in the local Mgmt-TypeSpec test project and regenerated outputs to reflect renamed expanded resources.
• Updated generated C# types/methods and the tspCodeModel.json snapshot to match the new resource names.

Reviewed changes

Copilot reviewed 5 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
eng/packages/http-client-csharp-mgmt/emitter/src/resource-metadata.ts	Introduces extraction + application of resource-name-mappings, including unused-key and collision diagnostics.
eng/packages/http-client-csharp-mgmt/emitter/src/resource-detection.ts	Applies overrides as a final step in the legacy buildArmProviderSchema path.
eng/packages/http-client-csharp-mgmt/emitter/src/resolve-arm-resources-converter.ts	Applies overrides as a final step in the resolveArmResources-based path.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/routedoperations.tsp	Demonstrates resource-name-mappings on an expandable resource model.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/tspCodeModel.json	Updates the code model snapshot to include the new clientOption and renamed resourceName metadata.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/Models/AzureGeneratorMgmtTypeSpecTestsContext.cs	Updates model registration attributes to reference renamed resource types.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/Extensions/MockableAzureGeneratorMgmtTypeSpecTestsArmClient.cs	Renames ArmClient helper methods to return renamed resource wrapper types.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/Extensions/AzureGeneratorMgmtTypeSpecTestsExtensions.cs	Renames extension methods and cref targets to match renamed resource wrappers.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/EventGridTopicResource.cs	Updates child-collection accessors to use renamed private endpoint connection wrappers.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/EventGridTopicPrivateEndpointConnectionResource.Serialization.cs	Regenerated serialization partial for the renamed topic child resource wrapper.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/EventGridTopicPrivateEndpointConnectionResource.cs	Renames the topic private endpoint connection resource wrapper and related diagnostics strings.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/EventGridTopicPrivateEndpointConnectionCollection.cs	Renames the topic private endpoint connection collection wrapper and related diagnostics strings.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/EventGridDomainResource.cs	Updates child-collection accessors to use renamed private endpoint connection wrappers.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/EventGridDomainPrivateEndpointConnectionResource.Serialization.cs	Regenerated serialization partial for the renamed domain child resource wrapper.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/EventGridDomainPrivateEndpointConnectionResource.cs	Renames the domain private endpoint connection resource wrapper and related diagnostics strings.
eng/packages/http-client-csharp-mgmt/generator/TestProjects/Local/Mgmt-TypeSpec/src/Generated/EventGridDomainPrivateEndpointConnectionCollection.cs	Renames the domain private endpoint connection collection wrapper and related diagnostics strings.

[ArcturusZhang]

I think the config should be apply to the Read operation instead of the model considering the existence of multi-path resources.
If we decide to add this to the Read operation, the resource id in the config looks redundant, therefore maybe this could be a simple name, or a map from resource type to resource name when it is expandable.