fix: support exactOptionalPropertyTypes in Transport interface#1507
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corvid-agent wants to merge 1 commit intomodelcontextprotocol:mainfrom
Open
fix: support exactOptionalPropertyTypes in Transport interface#1507corvid-agent wants to merge 1 commit intomodelcontextprotocol:mainfrom
corvid-agent wants to merge 1 commit intomodelcontextprotocol:mainfrom
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…tyTypes support When TypeScript's `exactOptionalPropertyTypes` is enabled, optional properties typed as `prop?: T` cannot be assigned `undefined` unless the type explicitly includes `| undefined`. This caused TS2420 errors when implementing the Transport interface. Update all optional callback/property types in the Transport interface, TransportSendOptions, and WebStandardStreamableHTTPServerTransportOptions to use the `| undefined` union pattern (e.g., `onclose?: (() => void) | undefined`). Fixes modelcontextprotocol#1314 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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@modelcontextprotocol/client
@modelcontextprotocol/server
@modelcontextprotocol/express
@modelcontextprotocol/hono
@modelcontextprotocol/node
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Summary
| undefinedto all optional properties in theTransportinterface,TransportSendOptionstype, andWebStandardStreamableHTTPServerTransportOptionsinterfaceexactOptionalPropertyTypescompiler option, which otherwise causesTS2420: Class incorrectly implements interfaceerrors when implementingTransportDetails
When
exactOptionalPropertyTypes: trueis enabled intsconfig.json, TypeScript distinguishes between "property may be missing" (prop?: T) and "property may be undefined" (prop?: T | undefined). Without the| undefinedunion, classes that declare optional properties (e.g.,onclose?: () => void) cannot be assignedundefinedat runtime, triggering type errors.Affected types:
Transport.onclose,Transport.onerror,Transport.onmessage,Transport.sessionId,Transport.setProtocolVersion,Transport.setSupportedProtocolVersionsTransportSendOptions.onresumptiontokenWebStandardStreamableHTTPServerTransportOptions.sessionIdGenerator,.onsessioninitialized,.onsessionclosedFixes #1314
Test plan
tsc --noEmitpasses for all packages (core, server, client, middleware/node, middleware/express, middleware/hono)| undefinedto optional property types🤖 Generated with Claude Code