typescript-monorepo-exports

name	typescript-monorepo-exports
description	Resolve TypeScript export conflicts and isolatedModules requirements in monorepo packages. Use when package index re-exports cause TS2308 (duplicate member) or TS1205 (export type required) errors.

TypeScript Monorepo Export Patterns

When to Use

• Package index uses export * from multiple modules
• Typecheck fails with TS2308: "Module X has already exported a member named 'Y'"
• Typecheck fails with TS1205: "Re-exporting a type when 'isolatedModules' is enabled requires using 'export type'"

TS2308: Duplicate Export Conflicts

Cause: Two or more source modules export types/functions with the same name. Re-exporting both via export * causes ambiguity.

Solution: Use explicit exports and exclude conflicting names from one source.

// ❌ Fails - both quiz-module-management and v2 export AddPageArgs
export * from "./internal/quiz-module-management";
export * from "./json/raw-quiz-config/v2";

// ✅ Fix - explicit exports from v2, exclude *Args (quiz-module-management has those)
export type { QuizConfig, NestedQuizConfig, Question, ... } from "./json/raw-quiz-config/v2";
export { calculateTotalPoints, createDefaultQuizConfig, addPage, ... } from "./json/raw-quiz-config/v2";

Alternative: Add a subpath export so consumers can import conflicting types directly:

// package.json
"exports": {
  ".": "./src/index.ts",
  "./json/raw-quiz-config/v2": "./src/json/raw-quiz-config/v2.ts"
}

TS1205: isolatedModules and export type

Cause: With isolatedModules: true, TypeScript cannot infer type-only vs value exports from a single export { type X, Y } statement.

Solution: Split type exports and value exports into separate statements:

// ❌ May fail with TS1205
export { type QuizConfig, calculateTotalPoints } from "./v2";

// ✅ Correct
export type { QuizConfig, NestedQuizConfig } from "./v2";
export { calculateTotalPoints, createDefaultQuizConfig } from "./v2";

Checklist

1. Identify which modules export the conflicting names
2. Decide which module "owns" each name for the main package export
3. Use explicit export type { ... } and export { ... } instead of export *
4. Add subpath exports for modules that need full access (including conflicting types)
5. Run typecheck to verify: bun typecheck or tsc --noEmit

Reference

See incident report: release-notes/incidents/2026-03-03-typescript-duplicate-export-conflicts.md