refactor(mcp_service): migrate index.js to TypeScript

[shayanshafii]

SUMMARY

Migrates the MCP service Node.js entry module from JavaScript to TypeScript, in line with the repo-wide "NO JavaScript files" modernization guidance in AGENTS.md.

superset/mcp_service/index.js exported a thin SupersetMCPServer wrapper class via CommonJS. It is now index.ts with:

• Typed constructor options (SupersetMCPServerOptions) and a fully-resolved internal options shape.
• A typed process: ChildProcess | null field (type imported from child_process).
• Removal of the previously-unused spawn/path-as-dead-code imports; path is now actually used.

The public CommonJS shape is preserved using export = SupersetMCPServer, so require('@superset/mcp-server') still returns the class directly (compiles to module.exports = SupersetMCPServer).

Because the compiled output now lives in dist/, start() resolves the bin script relative to the package root instead of the source dir:

// before (index.js, run from package root)
require('./bin/superset-mcp.js');
// after (index.ts -> dist/index.js)
require(path.join(__dirname, '..', 'bin', 'superset-mcp.js'));

Tooling added to make the TS source build/run, mirroring the existing superset-websocket Node package convention:

• tsconfig.json (module: commonjs, target: es2020, strict, declaration: true, outDir: dist).
• package.json: main -> dist/index.js, added types -> dist/index.d.ts, build/type-check scripts, and typescript + @types/node devDependencies. The bin/superset-mcp.js runner is unchanged and remains the package's bin entry.
• dist/ and node_modules/ are already covered by the root .gitignore, so no build artifacts are committed.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

N/A — no UI changes.

TESTING INSTRUCTIONS

cd superset/mcp_service
npm install
npm run type-check   # tsc --noEmit, passes
npm run build        # emits dist/index.js + dist/index.d.ts
# smoke test: export is still the class and instantiation works
node -e "const S=require('./dist/index.js'); const s=new S({port:6000}); s.stop(); console.log(S.name, s instanceof S);"
# -> SupersetMCPServer true

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

Link to Devin session: https://app.devin.ai/sessions/5c09535882164e0f9746046ea0776643
Requested by: @shayanshafii

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[devin-ai-integration]

Devin Review found 1 potential issue.

[devin-ai-integration]

🚩 Pre-existing: stop() is a no-op because start() never sets this.process

The start() method at superset/mcp_service/index.ts:67-71 calls require() to load the bin script, which internally spawns a Python child process. However, that child process reference is local to the bin script (superset/mcp_service/bin/superset-mcp.js:250) and is never exported or returned. As a result, this.process remains null after start(), and stop() at line 73-78 can never actually kill the spawned process. This is unchanged from the original JS — the old code also never set this.process — but it means the class's lifecycle management is incomplete. If anyone ever calls stop(), it silently does nothing.

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[devin-ai-integration]

Thanks — agreed, and as the note says this is pre-existing: the original index.js also never set this.process, so stop() has always been a no-op. This PR is intentionally a behavior-preserving JS→TS migration, so I've left the lifecycle logic unchanged rather than expanding scope here. Properly wiring up start()/stop() (e.g. having the bin runner expose the spawned ChildProcess so it can be tracked and killed) would be a good follow-up, but it's a functional change beyond this migration.