chore: extend library interfaces to allow injecting a custom connection error handler MCP-132

[himanshusinghs]

Proposed changes

We're expanding the transport runner and server's interface to accept a custom connection error handler so that library consumers can provide their own mechanism of handling connection error and have an opportunity to act on them.

This will allow VSCode to provide its own ConnectionErrorHandler and thus modify the tool responses in case of connection problems.

Checklist

• I have signed the MongoDB CLA

[himanshusinghs]

This entire file is a cut of existing logic in MongodbToolBase.

[Copilot]

Pull Request Overview

This PR extends the MongoDB MCP library to support custom connection error handlers, allowing consumers to inject their own error handling logic for connection-related errors instead of relying solely on the default implementation.

Key changes include:

• Refactored transport runners to accept configuration objects with optional connection error handlers
• Created a new ConnectionErrorHandler interface and default implementation
• Modified the Server class to use injected connection error handlers
• Updated MongoDB tools to delegate connection error handling to the injected handler

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/common/connectionErrorHandler.ts	New file defining the connection error handler interface and default implementation
src/common/errors.ts	Made MongoDBError generic to support type-safe error code handling
src/transports/base.ts	Added TransportRunnerConfig type and updated base class to support connection error handlers
src/transports/stdio.ts	Updated constructor to use new configuration object pattern
src/transports/streamableHttp.ts	Updated constructor to use new configuration object pattern
src/server.ts	Added connection error handler to server options and implementation
src/tools/mongodb/mongodbTool.ts	Refactored to use injected connection error handler instead of hardcoded logic
src/index.ts	Updated transport runner instantiation to use new configuration objects
tests/integration/transports/streamableHttp.test.ts	Updated test instantiation to use new configuration pattern
tests/integration/tools/mongodb/mongodbTool.test.ts	Added comprehensive tests for connection error handler functionality
tests/integration/helpers.ts	Updated test helper to include default connection error handler

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[coveralls]

Pull Request Test Coverage Report for Build 17429932259

Details

• 92 of 106 (86.79%) changed or added relevant lines in 9 files are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.2%) to 81.125%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/lib.ts	0	1	0.0%
src/transports/stdio.ts	3	4	75.0%
src/common/connectionErrorHandler.ts	60	62	96.77%
src/tools/mongodb/mongodbTool.ts	9	11	81.82%
src/index.ts	0	8	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/lib.ts	1	0.0%
src/transports/stdio.ts	1	63.33%

Totals
Change from base Build 17411863932:	0.2%
Covered Lines:	4579
Relevant Lines:	5556

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💛 - Coveralls