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Lambda Doctor — Implementation Guide

Project scaffold is ready. Implement in the following order.

Implementation Order

1. src/analyzers/bundle-size.ts

  • Scan all files under node_modules/ using fast-glob
  • Group scoped packages correctly (@aws-sdk/client-dynamodb → @aws-sdk/client-dynamodb)
  • Collect file sizes via fs.stat
  • Report top 10 largest dependencies
  • Thresholds: >50MB critical, >10MB warning, single dep >5MB critical, >1MB warning

2. src/analyzers/heavy-dependencies.ts

  • Read package.json, split dependencies and devDependencies
  • Check each dependency against known-heavy-packages.ts
  • Flag dev tools (typescript, ts-node) in dependencies as critical
  • Add alternative and estimatedSavingsMs to each diagnostic

3. src/analyzers/import-analysis.ts

  • Find .ts, .js, .mjs files using fast-glob (excluding node_modules)
  • Extract import/require patterns with regex:
    • ESM: /^import\s+.*\s+from\s+['"](.+)['"]/gm
    • CJS: /^(?:const|let|var)\s+.*=\s*require\(['"](.+)['"]\)/gm
  • Top-level vs function-body detection: line indentation 0-1 = top-level
  • Flag top-level imports of heavy packages
  • Flag import * as patterns (blocks tree-shaking)

4. src/analyzers/aws-sdk.ts

  • aws-sdk (v2) in package.json → critical
  • @aws-sdk/client-* present → good, count them
  • Both v2 and v3 → warning (incomplete migration)
  • More than 5 @aws-sdk clients → info (too many clients)
  • @aws-sdk/client-sso import in source → warning (unnecessary in Lambda)

5. src/analyzers/bundler-detection.ts

  • Check devDependencies for bundlers: esbuild, webpack, rollup, tsup, parcel
  • Check for config files: webpack.config., rollup.config., tsup.config., esbuild.config.
  • Check package.json scripts for bundler keywords
  • Check serverless.yml for serverless-esbuild or serverless-webpack
  • Check for "type": "module" (ESM)
  • No bundler found → critical (biggest optimization opportunity)

6. src/reporters/console.ts

  • Colored output with chalk
  • Severity icon mapping: critical=🔴, warning=⚠️, info=💡
  • Bundle size breakdown (top dependencies table)
  • Diagnostics sorted by severity
  • Footer with total estimated improvement

7. src/bin/cli.ts

  • Show ora spinner during analysis
  • Error handling: meaningful messages for missing path or package.json
  • JSON output format support
  • Exit code 1 if critical issues found

Quality Standards

  • Each analyzer returns its own AnalyzerResult
  • All file I/O must be async (fs/promises)
  • Every diagnostic must have: title, description, recommendation, estimatedImpactMs
  • No analyzer should crash — return empty result on error, log warning to console
  • Test fixtures: unhealthy-lambda must have at least 8 issues
  • Test fixtures: healthy-lambda must have 0 critical issues

Run & Verify

npm install
npm run build
npm test

# Manual test with fixtures
node dist/bin/cli.js analyze test/fixtures/unhealthy-lambda
node dist/bin/cli.js analyze test/fixtures/healthy-lambda
node dist/bin/cli.js analyze test/fixtures/unhealthy-lambda --format json