Remove obsolete APIs from codebase

[Copilot]

Remove Obsolete APIs

This PR removes APIs marked with [Obsolete] that no longer need to be kept for backward compatibility, per issue #774.

Summary

Successfully removed obsolete APIs from the codebase:

• 1 obsolete class (McpServerFactory)
• 23 obsolete extension methods
• 17 obsolete properties from capability classes
• 3 obsolete interfaces (IMcpEndpoint, IMcpClient, IMcpServer)
• 1 obsolete factory class (McpClientFactory)
• 1 file (McpClientExtensions.cs) - removed as methods were moved to AIContentExtensions.cs in PR Add tools support to sampling #976

This PR also introduces the infrastructure to support custom diagnostics for both obsoletions and experimental APIs.

Two obsolete enum schema classes remain for backward compatibility:

• LegacyTitledEnumSchema and EnumSchema, per (#969) Implement SEP-1330: Standards-compliant enum schemas for elicitation
  • A custom MCP9001 diagnostic ID is assigned to these APIs, linking to the SEP issue

[eiriktsarpalis]

@copilot please address the merge conflicts in your branch.

[Copilot]

@copilot please address the merge conflicts in your branch.

Merge conflicts resolved in commit cd8f7ae. The conflicts were modify/delete conflicts where the test files for obsolete extension methods were modified in main (to add #pragma warning disable CS0618) but were deleted in this branch. Since these tests were specifically testing obsolete APIs that have been removed, the correct resolution was to keep them deleted.

[eiriktsarpalis]

@copilot your changes failed to fix all merge conflicts.

[Copilot]

@copilot your changes failed to fix all merge conflicts.

All merge conflicts have been resolved in commit 3d20111. The conflicts were from PR #984 which removed Id = default assignments from the same test files I deleted. Since these test files test obsolete APIs that have been removed, keeping them deleted is the correct resolution.

[MackinnonBuck]

@copilot it looks like there are more obsolete APIs you need to remove:

• IMcpEndpoint
• IMcpClient
• McpClientFactory
• IMcpServer

[stephentoub]

@copilot You missed the following APIs that are marked as [Obsolete]:

• class LegacyTitledEnumSchema
• class EnumSchema

When removing these, there is code in ElicitRequestParams that needs to be removed:

• The case "enumNames" block is no longer needed, and the enumNames variable does not need to be defined or set

• The block for if (enumNames is not null) will need to be removed as psd = new EnumSchema will no longer work. The else block will now always apply.

• The case LegacyTitledEnumSchema legacyEnum block needs to be deleted

• Unit tests specific to EnumSchema or LegacyTitledEnumSchema need to be deleted

• Unit tests with EnumSchema or LegacyTitledEnumSchema scenarios mixed in need to have those scenarios removed from the tests; where applicable, scenarios for the following enum schemas should be used or added:

  • TitledMultiSelectEnumSchema
  • TitledSingleSelectEnumSchema
  • UntitledMultiSelectEnumSchema
  • UntitledSingleSelectEnumSchema

Additionally, all places where #pragma warning disable CS0618 is applied need to be removed, properly formatting the code around that removed block to ensure no double blank lines are left behind.

After these changes, there should not be any code search results for "[Obsolete" or "0618".

@jeffhandley, those just got merged as part of #969, and I believe they'd still be needed for backwards wire compatibility.

/**
* Use TitledSingleSelectEnumSchema instead.
* This interface will be removed in a future version.
*/
export interface LegacyTitledEnumSchema {
type: "string";
title?: string;
description?: string;
enum: string[];
/**
* (Legacy) Display names for enum values.
* Non-standard according to JSON schema 2020-12.
*/
enumNames?: string[];
default?: string;
}
// Union type for all enum schemas
export type EnumSchema =
| SingleSelectEnumSchema
| MultiSelectEnumSchema
| LegacyTitledEnumSchema;

[MackinnonBuck]

those just got merged as part of #969, and I believe they'd still be needed for backwards wire compatibility.

@stephentoub@jeffhandley Sounds like we should revert 93a6877 and 186d85c, then?

[jeffhandley]

Yeah, but we should organize those classes and tests to distinguish them better, and apply MCP obsoletion diagnostic IDs to these new obsoletions since they will survive into 1.0.0. I was getting started on it and I can finish this up, @MackinnonBuck.