TypeScript SDD Constitution

 

Core Principles

I. Specification-First Development

Every feature, module, and component must have a complete specification before implementation. Specifications define interfaces using TypeScript types, expected behaviors through JSDoc comments, and test scenarios via test specification files. No code merges without corresponding .spec.md and .d.ts files that fully describe the implementation contract.

II. Type-Safety Enforcement

TypeScript strict mode is mandatory across the entire codebase. All data flows must be fully typed with explicit interfaces - no any types except in exceptional, documented cases. Runtime type validation required at all system boundaries using libraries like zod or io-ts. Type definitions serve as executable specifications that compile-time verify implementation compliance.

III. Test-Driven Implementation (NON-NEGOTIABLE)

Strict TDD cycle: Write failing tests from specifications → Get stakeholder approval → Tests must fail → Implement minimal code to pass → Refactor with confidence. Test files must be created before implementation files. Coverage requirements: 100% for business logic, 90% overall. Tests are specifications expressed as executable code.

IV. Module Architecture

Every feature implemented as an independent, publishable npm package within a monorepo structure. Modules communicate only through well-defined, versioned interfaces. Each module maintains its own package.json, tsconfig.json, README, and changelog. Dependencies explicitly declared - no implicit coupling allowed. Modules must be independently deployable and testable.

V. CLI-First Interface

Every module exposes primary functionality through a CLI using commander.js or yargs. Standard I/O protocol: JSON input via stdin/args, JSON/text output to stdout, errors to stderr with structured error codes. CLI serves as both user interface and integration testing interface. All CLI commands must be idempotent and composable.

VI. Observability & Debugging

Comprehensive structured logging using winston or pino with correlation IDs across module boundaries. Debug mode for all modules via DEBUG environment variable. Source maps required for all compiled code. OpenTelemetry instrumentation for distributed tracing. Every error must include actionable context and recovery suggestions.

VII. Progressive Complexity

Start with the simplest working implementation that satisfies the specification. YAGNI (You Aren't Gonna Need It) strictly enforced - no speculative features. Complexity added only when proven necessary through documented requirements. Premature optimization is forbidden without performance specifications and benchmarks.

TypeScript Standards

Type System Requirements

  • Compiler Options: strict: true, noImplicitAny: true, strictNullChecks: true, noUncheckedIndexedAccess: true
  • Type Coverage: Minimum 95% type coverage using type-coverage tool
  • Generic Constraints: All generics must have explicit constraints
  • Discriminated Unions: Preferred over class hierarchies for polymorphism
  • Branded Types: Use for domain primitives (e.g., UserId, Email)

Code Organization

  • Barrel Exports: Each module has single entry point via index.ts
  • File Structure: src/ for source, lib/ for compiled, test/ for tests, spec/ for specifications
  • Naming Conventions: PascalCase for types/interfaces, camelCase for functions/variables, SCREAMING_SNAKE_CASE for constants
  • Import Order: Node built-ins → External packages → Internal packages → Relative imports
  • File Size: Maximum 300 lines per file, prefer smaller focused modules

Async Patterns

  • Promise-Based: All async operations use Promises, no callbacks
  • Error Handling: Every Promise must have explicit error handling
  • Async/Await: Preferred over .then() chains for readability
  • Concurrency Control: Use p-limit or similar for controlled parallelism
  • Timeouts: All async operations must have configurable timeouts

Quality Gates

Pre-Commit Checks

  1. Specification Verification: Ensure .spec.md exists and is up-to-date
  2. Type Check: tsc --noEmit must pass
  3. Linting: ESLint with @typescript-eslint strict configuration
  4. Format: Prettier with consistent configuration
  5. Test Execution: All unit tests must pass
  6. Coverage Check: Meet minimum coverage thresholds

Pull Request Requirements

  • Specification Review: Spec changes reviewed before implementation
  • Type Safety Review: No new any types or type assertions without justification
  • Test Review: Tests reviewed for completeness against specifications
  • Performance Impact: Benchmarks for performance-critical paths
  • Breaking Change Assessment: Semantic versioning impact documented
  • Documentation Update: README, API docs, and inline comments current

Continuous Integration

  • Matrix Testing: Test against multiple Node.js versions (LTS versions)
  • Dependency Audit: npm audit must pass with no high/critical vulnerabilities
  • Bundle Size Check: Monitor and limit bundle size growth
  • Integration Tests: Full end-to-end tests for critical user paths
  • Performance Regression: Automated performance benchmarks with thresholds

Development Workflow

Specification Phase

  1. Create specification document in spec/[feature-name].spec.md
  2. Define TypeScript interfaces in spec/[feature-name].types.ts
  3. Write test specifications in spec/[feature-name].test-spec.ts
  4. Get stakeholder approval on specifications
  5. Create implementation ticket with specification links

Implementation Phase

  1. Create test file implementing test specifications
  2. Verify all tests fail appropriately
  3. Implement minimal code to pass tests
  4. Refactor while maintaining green tests
  5. Update documentation and examples
  6. Submit PR with specification compliance checklist

Release Process

  1. Version bump following semantic versioning
  2. Update CHANGELOG.md with breaking changes highlighted
  3. Run full regression test suite
  4. Generate API documentation from TypeScript definitions
  5. Publish to npm registry with appropriate tags
  6. Update dependent modules to use new version

Toolchain Requirements

Essential Tools

  • TypeScript: Latest stable version, upgraded quarterly
  • Node.js: Latest LTS version for development
  • Package Manager: pnpm for monorepo management
  • Testing: Jest with ts-jest for unit tests, Playwright for E2E
  • Linting: ESLint with TypeScript plugins
  • Formatting: Prettier with explicit configuration
  • Documentation: TypeDoc for API documentation

Development Tools

  • Build: esbuild or swc for fast compilation
  • Watch Mode: tsx or ts-node-dev for development
  • Debugging: Node.js inspector with source map support
  • Profiling: clinic.js for performance analysis
  • Security: Snyk or npm audit for vulnerability scanning

Governance

Constitution Authority

This constitution supersedes all other development practices and guidelines. Any deviation requires explicit amendment through the defined process. All code reviews must verify constitutional compliance before approval. Violations must be documented with justification and remediation timeline.

Amendment Process

Amendments require: Written proposal with rationale, impact analysis on existing codebase, migration plan for affected code, 2/3 team approval vote, and 1-week comment period. Emergency amendments allowed for security issues with retroactive approval.

Compliance Verification

Weekly automated constitution compliance reports. Monthly manual audit of randomly selected modules. Quarterly full codebase constitutional review. Annual constitution effectiveness assessment with team feedback.

Escalation Path

  1. Team discussion for minor violations
  2. Tech lead review for repeated violations
  3. Stakeholder intervention for systemic issues
  4. Constitution amendment for irreconcilable conflicts

Version: 1.0.0 | Ratified: 2025-01-20 | Last Amended: 2025-01-20

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