Fix API version enum collisions in multservice clients

[Copilot]

PR #10061 unconditionally used the full namespace for API version enum names in multi-service scenarios. This produces unnecessarily verbose names when services have distinct last namespace segments. This PR changes the logic to only use the full namespace when there's an actual collision, and restores the ClientHelper.BuildNameForService helper for proper prefix/suffix-aware naming. The collision-aware naming applies to all multi-service generated members — enum type names, version property names, and latest version field names all use BuildNameForService by default, falling back to a segment-by-segment resolution when last segments collide. The enum type naming follows the {X}ServiceVersion pattern (e.g., KeyVaultServiceVersion) rather than Service{X}Version.

When last segments collide, the new ClientHelper.GetShortestUniqueNamespacePrefix method progressively adds namespace segments from right to left until a unique suffix is found, producing shorter names than the previous full-namespace approach. When multiple enums share the exact same full namespace (e.g., when the emitter remaps both services to the same C# output namespace), the enum's input name is appended for disambiguation to prevent duplicate member names.

Behavior

Namespaces	Member	Before (PR #10061)	After (no collision)	After (last segment collision)	After (full namespace collision)
Sample.KeyVault, Sample.Storage	Enum type	SampleKeyVaultVersion	KeyVaultServiceVersion	—	—
Sample.KeyVault, Sample.Storage	Version property	SampleKeyVaultApiVersion	KeyVaultApiVersion	—	—
Sample.KeyVault, Sample.Storage	Latest field	LatestServiceKeyVaultVersion	LatestKeyVaultVersion	—	—
Azure.One.Tests, Azure.Two.Tests	Enum type	AzureOneTestsVersion	—	ServiceOneTestsVersion (shortest unique: 2 segments)	—
Azure.One.Tests, Azure.Two.Tests	Version property	AzureOneTestsApiVersion	—	ServiceOneTestsApiVersion (shortest unique: 2 segments)	—
Same namespace for both enums	Enum type	—	—	—	{Namespace}{EnumName}Version (disambiguated by input name)

Changes

• ClientHelper.cs — restored BuildNameForService helper (removed in PR Fix duplicate API version field names for multi-service clients with colliding namespaces #10061) that extracts the last namespace segment and ensures proper prefix/suffix without duplication; added shared GetLastNamespaceSegment and HasLastSegmentCollision static helpers; added GetShortestUniqueNamespacePrefix that progressively adds segments from right to left until finding a unique suffix, falling back to appending the enum input name when namespaces are identical
• ClientHelperTests.cs — restored all 22 tests for BuildNameForService
• ApiVersionEnumProvider.BuildName() — uses ClientHelper.BuildNameForService with empty prefix and "ServiceVersion" suffix for the non-collision case, producing {X}ServiceVersion names; uses GetShortestUniqueNamespacePrefix for segment-by-segment resolution when last segments collide
• ClientOptionsProvider.BuildVersionProperties() — uses ClientHelper.BuildNameForService for version property names in the non-collision case; uses GetShortestUniqueNamespacePrefix when last segments collide
• ClientOptionsProvider.BuildLatestVersionsFields() — uses ClientHelper.BuildNameForService for latest version field names in the non-collision case; uses GetShortestUniqueNamespacePrefix when last segments collide
• Tests — updated assertions and expected test data files (ClientOptionsProvider, ClientProvider, RestClientProvider) for member name changes; added MultiServiceClient_WithCollidingLastSegments_UsesShortestUniquePrefix test with TestData golden file validation; added MultiServiceClient_SameLastSegment_ProducesUniqueVersionEnums test; added MultiServiceClient_UniqueNamespaces_ProducesUniqueVersionEnums test simulating distinct service namespaces; added MultiServiceClient_SameNamespace_ProducesUniqueVersionEnums test for the same-namespace scenario where the emitter remaps both services to the same C# output namespace

Original prompt

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This section details on the original issue you should resolve

<issue_title>Only Use Full Namespace for Api Version Enum When There are Conflicts</issue_title>
<issue_description>Follow up to #10061.

This PR introduced a change to avoid collisions in the generated api version enums in the multi-service scenario by using the full namespace of the enum as the name. We should update this to only do this whenever there is a collision in the generated names.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Only Use Full Namespace for Api Version Enum When There are Collisions #10107

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[jorgerangel-msft]

@copilot we also need to ensure we regenerate all the test projects.

[Copilot]

@copilot we also need to ensure we regenerate all the test projects.

Ran eng/scripts/Generate.ps1 to regenerate all test projects. No files changed — all existing test projects are single-service, so the multi-service naming logic doesn't affect them. All unit tests pass (ApiVersionEnumProviderTests: 8, ClientHelperTests: 22, ClientOptionsProviderTests: 31, ClientProviderTests: 238).

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[jorgerangel-msft]

@copilot lets refactor our approach here. Lets only use the naming changes from #10061 when the generated members will collide. Otherwise, lets default to the previous approach prior to the PR which was to use the client helper to create the member name.

[Copilot]

@copilot lets refactor our approach here. Lets only use the naming changes from #10061 when the generated members will collide. Otherwise, lets default to the...

Refactored to apply BuildNameForService for ALL multi-service members (enum type, version properties, field names) when there's no collision. Full namespace naming from PR #10061 is now only used as fallback when last segments collide. Updated 10 test data files and 2 test assertions, and regenerated all test projects (no changes since they're all single-service). See commit 10024bc.

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I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/typespec/typespec/website/node_modules/.bin/../astro/bin/astro.mjs build node pec/�� tput-dir ../../w--llmstxt sh .2_tmp_5782_0/no../../website/src/content/docs/docs/emitters/openapi3/reference --no-emit ture /.bin/sh node /nod�� rs && pnpm build:src tsconfig.build.json 0/x64/lib/node_modules/npm/node_--output-dir build');process.node l/reference /.bin/node node (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

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[Copilot]

@copilot lets change the default naming of the ServiceVersion enum in the multiservice client scenario. Instead of ServiceXVersion lets do XServiceVersion. So services Foo and Bar in a client would ha...

Changed the enum naming from Service{X}Version to {X}ServiceVersion. The BuildName() call now uses BuildNameForService(serviceNamespace, string.Empty, ApiVersionEnumName) which produces KeyVaultServiceVersion, StorageServiceVersion, etc. Updated 4 golden test data files and 2 test assertions. All 299 tests pass. See commit 352b1da.

[jorgerangel-msft]

@copilot it looks that the original bug wasn't fully fixed per this comment. Validate the fix by adding unit tests to simulate the spec defined in the [original issue[(https://github.com//issues/10055#issue-4086914483).

[Copilot]

@copilot it looks that the original bug wasn't fully fixed per this comment. Validate the fix by adding un...

Added two unit tests simulating the original issue #10055 spec, and fixed the same-namespace collision case:

1. MultiServiceClient_OriginalIssueSpec_ProducesUniqueVersionEnums — simulates the exact scenario from the issue with ServiceOne/ServiceTwo namespaces and Versions enums. Validates Fields and Methods access don't crash, enum names are unique (ServiceOneServiceVersion, ServiceTwoServiceVersion), and golden file output matches.

2. MultiServiceClient_SameNamespace_ProducesUniqueVersionEnums — simulates the tspconfig-remapped scenario where both enums share the exact same namespace (Azure.Generator.MgmtTypeSpec.MultiService.Tests). This was the actual crash site — our previous code produced duplicate names. Fixed by adding ClientHelper.HasFullNamespaceCollision() which detects same-namespace collisions and appends the enum's input name for disambiguation.

The fix adds a third tier to the naming logic: when even the full namespace produces duplicates (same namespace), it appends the enum input name (e.g., AzureGeneratorMgmtTypeSpecMultiServiceTestsServiceOneVersionsVersion). All 301 tests pass. See commit 1d1db57.