Add custom fetch support to transports

[cliffhall]

Summary

• add a fetch option to SSEClientTransport and StreamableHTTPClientTransport
• use the custom fetch implementation for SSE, HTTP POST and DELETE requests
• ensure custom fetch can add auth headers in tests

Testing

• npm install
• npm test

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https://chatgpt.com/codex/tasks/task_e_686405a312f48331b41322eb4cee87cb

[gemini-code-assist]

Summary of Changes

Hello @cliffhall, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant enhancement by allowing the SSEClientTransport and StreamableHTTPClientTransport classes to accept a custom fetch implementation. This provides greater flexibility for integrating with various network environments, enabling custom authentication flows, proxying, or leveraging specific network libraries, thereby giving users more control over how network requests are made by these transports.

Highlights

• Custom Fetch API Integration: I've added a new fetch option to both SSEClientTransportOptions and StreamableHTTPClientTransportOptions, allowing consumers to provide their own fetch-like function for network requests.
• Enhanced Network Request Control: The provided custom fetch implementation is now utilized for all relevant network operations within both transports, including SSE connections (GET), JSON-RPC message sending (POST), and session termination (DELETE).
• Improved Test Coverage: New test cases have been added for both SSEClientTransport and StreamableHTTPClientTransport to ensure that the custom fetch implementation is correctly used and can modify request headers, specifically for authentication.

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[gemini-code-assist]

Code Review

This pull request introduces the ability to use a custom fetch implementation for network requests in SSEClientTransport and StreamableHTTPClientTransport. The changes look good, but I've added some suggestions to consider using the nullish coalescing operator for conciseness.

[gemini-code-assist]

Code Review

This pull request adds support for a custom fetch implementation to the SSEClientTransport and StreamableHTTPClientTransport. I've provided suggestions to improve code maintainability and test robustness.

[cliffhall]

@gemini-code-assist summary

[gemini-code-assist]

Summary of Changes

This pull request significantly enhances the flexibility of the SSEClientTransport and StreamableHTTPClientTransport classes by enabling the injection of a custom fetch implementation. This change empowers users to exert fine-grained control over network requests, facilitating advanced use cases such as custom authentication flows or specialized request handling, thereby improving the adaptability of the transport layer.

Highlights

• Custom Fetch Support: Added a fetch option to SSEClientTransport and StreamableHTTPClientTransport constructors, allowing consumers to provide their own custom fetch implementation for network requests.
• Comprehensive Integration: The custom fetch implementation is now utilized for all internal network operations within these transports, including initial SSE connections (GET), sending messages (POST), and session termination (DELETE).
• Type Standardization: Introduced a shared FetchLike type definition in src/shared/transport.ts to ensure consistent typing for custom fetch functions across the codebase.
• Enhanced Test Coverage: New test cases were added to verify the correct usage and behavior of the custom fetch implementation, specifically ensuring proper authentication header propagation for various request types.

Changelog

• src/client/sse.test.ts
  • Added a new test case to verify that SSEClientTransport correctly utilizes a custom fetch implementation for both initial connection and subsequent POST requests, ensuring proper header propagation.
• src/client/sse.ts
  • Imported the new FetchLike type from src/shared/transport.ts.
  • Added a fetch option to SSEClientTransportOptions and a corresponding private _fetch property.
  • Updated internal fetch calls within _startOrAuth() and send() methods to use the provided custom fetch or fall back to the global fetch.
  • Applied nullish coalescing operator (??) for fetch fallback logic as per review suggestions.
• src/client/streamableHttp.test.ts
  • Imported the StartSSEOptions interface for improved type safety in tests.
  • Added a new test case to confirm StreamableHTTPClientTransport uses the custom fetch implementation for all its network operations, including authentication.
  • Minor formatting adjustments.
• src/client/streamableHttp.ts
  • Imported the new FetchLike type from src/shared/transport.ts.
  • Exported the StartSSEOptions interface.
  • Added a fetch option to StreamableHTTPClientTransportOptions and a corresponding private _fetch property.
  • Modified _startOrAuthSse(), send(), and terminate() methods to use the custom fetch implementation for their respective network requests.
  • Applied nullish coalescing operator (??) for fetch fallback logic as per review suggestions.
  • Minor formatting adjustments.
• src/shared/transport.ts
  • Defined and exported the FetchLike type, standardizing the signature for custom fetch functions across the codebase.
  • Minor formatting adjustments to comments.

Activity

• gemini-code-assist[bot] provided several suggestions to use the nullish coalescing operator (??) instead of the logical OR operator (||) for fetch fallback logic in src/client/sse.ts and src/client/streamableHttp.ts. These suggestions were addressed by the author.
• gemini-code-assist[bot] recommended moving the FetchLike type definition to a shared location (src/shared/transport.ts) to avoid duplication, which the author fixed.
• gemini-code-assist[bot] suggested more specific assertions in src/client/sse.test.ts to verify fetchWithAuth calls, which the author implemented.
• gemini-code-assist[bot] advised exporting the StartSSEOptions interface from src/client/streamableHttp.ts for better type safety in tests, which the author also addressed.
• cliffhall (the author) requested a summary from the bot.